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inoLabMulti 720

ba75442e01 03/2004

ba75442e

Operating Manual

Measuring Instrumentfor pH, Redox, Dissolved Oxygen

and Conductivity

Multi

720


2/82

Accuracy when

going to press

The use of advanced technology and the high quality stan-

dard of our instruments are the result of continuous develop-

ment. This may result in differences between this operatingmanual and your instrument.

We cannot guarantee that there are absolutely no errors in

this manual. We are sure you will understand that we cannot

accept any legal claims resulting from the data, figures or

descriptions.

Warranty declara-

tion

The designated instrument is covered by a warranty of three

years from the date of purchase.

The instrument warranty extends to manufacturing faults

that are determined within the period of warranty.

The warranty excludes components that are replaced during

maintenance such as batteries, etc.

The warranty claim extends to restoring the instrument to

readiness for use but not, however, to any further claim for

damages. Improper handling or unauthorized opening of the

instrument invalidates any warranty claim.

To ascertain the warranty liability, return the instrument and

proof of purchase together with the date of purchase freight

paid or prepaid.

Copyright Weilheim 2004, WTW GmbH

Reprinting - even as excerpts - is only allowed with the ex-

plicit written authorization of WTW GmbH, Weilheim.

Printed in Germany.


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Multi 720 Contents

85

1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

1.1 Keypad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

1.2 Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

1.3 Sockets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

1.4 Operating structure. . . . . . . . . . . . . . . . . . . . . . 90

2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

2.1 Authorized use . . . . . . . . . . . . . . . . . . . . . . . . . 92

2.2 General safety instructions. . . . . . . . . . . . . . . . 92

3 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . 95

4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

4.1 Switch on the instrument . . . . . . . . . . . . . . . . . 97

4.2 Measuring the pH value/Redox voltage . . . . . . 98

4.2.1 Measuring the pH value . . . . . . . . . . . 100

4.2.2 Measuring the Redox voltage . . . . . . . 101

4.3 Calibrating for pH measurements. . . . . . . . . . 102

4.3.1 AutoCal TEC . . . . . . . . . . . . . . . . . . . . 104

4.3.2 AutoCal DIN . . . . . . . . . . . . . . . . . . . . 106

4.3.3 ConCal . . . . . . . . . . . . . . . . . . . . . . . . 108

4.4 Measuring the dissolved oxygen . . . . . . . . . . 111

4.4.1 Oxygen concentration . . . . . . . . . . . . . 112

4.4.2 Oxygen saturation . . . . . . . . . . . . . . . . 113

4.4.3 Oxygen partial pressure . . . . . . . . . . . 114

4.4.4 AutoRead AR (drift control) . . . . . . . . . 114

4.5 Calibrating for D. O. measurements. . . . . . . . 116

4.5.1 Starting the calibration. . . . . . . . . . . . . 118

4.5.2 Entering the salt content (salinity) . . . . 120

4.6 Measuring the conductivity. . . . . . . . . . . . . . . 121

4.6.1 Conductivity / Specific resistance . . . . 123

4.6.2 Salinity. . . . . . . . . . . . . . . . . . . . . . . . . 124

4.6.3 TDS (total dissolved solids) . . . . . . . . . 125

4.6.4 AutoRead AR (Drift control). . . . . . . . . 126

4.7 Determining/setting up the cell constant [C]. . 127

4.7.1 Determining the cell constant

(calibration in control standard) . . . . . . 127


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Contents Multi 720

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4.7.2 Setting up the cell constant . . . . . . . . . 130

4.8 Setting up the temperature compensation TC 133

4.9 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . 137

4.10 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

5 Maintenance, cleaning, disposal. . . . . . . . . . 143

5.1 Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . 143

5.2 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

5.3 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

6 What to do if... . . . . . . . . . . . . . . . . . . . . . . . . . 1456.1 pH system messages . . . . . . . . . . . . . . . . . . . 145

6.2 Oxygen system messages . . . . . . . . . . . . . . . 147

6.3 Conductivity system messages . . . . . . . . . . . 149

6.4 General errors . . . . . . . . . . . . . . . . . . . . . . . . 149

7 Technical Data . . . . . . . . . . . . . . . . . . . . . . . . 151

7.1 General data. . . . . . . . . . . . . . . . . . . . . . . . . . 151

7.2 pH/Redox measurement . . . . . . . . . . . . . . . . 1537.3 Oxygen measurement . . . . . . . . . . . . . . . . . . 154

7.4 Conductivity measurement. . . . . . . . . . . . . . . 155

8 Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157


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Multi 720 Overview

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1 Overview

The compact inoLabMulti 720 precision measuring instru-ment lets you perform pH, Redox, D. O., and conductivity

measurements rapidly and reliably. The inoLabMulti 720

provides the highest degree of operating comfort, reliability

and measuring safety for all applications.

The proven OxiCaland MultiCalcalibration procedures

and special AutoReadfunction support your work with the

instrument.

NoteThe measuring instrument can also be delivered as part of

a set.

Information on this and other accessories is available in the

WTW catalog LABORATORYAND FIELD INSTRUMENTATION or

via the Internet.

1 Keypad

2 Display

3 Sockets

Multi

720

3

2

1


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Overview Multi 720

88

1.1 Keypad

1 Measuring instrument ON/OFF

2 Select measuring mode

3 Call up calibration procedure

4 Activate/deactivate AutoRead

5 Confirm inputs, start AutoRead

6 Select measuring mode, increase values,

scroll

7 Select measuring mode, reduce values,

scroll

4

3

2

1

7

6

5


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Multi 720 Overview

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1.2 Display

1.3 Sockets

Caution

Only connect probes to the instrument that cannot feed ex-

cessive voltages or currents (> SELV and > circuit with cur-

rent limiter). Almost all commercial electrodes - especially

WTW electrodes - meet these requirements.

On socket 4, use the WTW probe StirrOx Gonly.

Connectors:

1 Dissolved oxygen probe or conductivity measuring cell

2 pH/Redox electrode

3 Temperature probe

4 Stirrer (StirrOx G)

5 Reference electrode

6 Mains power supply (option)

tatus ne

Measured value display

Function and

temperature display

1 2 3 4

56


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Overview Multi 720

90

1.4 Operating structure

The following overview diagram shows which keys you have

to press to select between the different measuring modes:

Note

When a D. O. probe or a conductivity measuring cell with

temperature probe is connected, the measuring instrumentrecognizes the probe or measuring cell and automatically

switches to the oxygen measuring mode or conductivity

measuring mode last selected. As soon as the probe/mea-

suring cell is disconnected, the instrument switches to the

pH or Redox measuring mode.


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Multi 720 Safety

91

2 Safety

This operating manual contains basic instructions that youmust follow during the commissioning, operation and main-

tenance of the instrument. Consequently, all responsible

personnel must read this operating manual before working

with the instrument.

The operating manual must always be available within the

vicinity of the instrument.

Target group This measuring instrument was developed for use in the lab-

oratory.

Thus, we assume that, as a result of their professional train-

ing and experience, the operators will know the necessary

safety precautions to take when handling chemicals.

Symbols used

Cautionindicates instructions that have to be followed to prevent

damage to your instrument.

Warning

indicates instructions that have to be followed to protect

yourself and the instrument from dangerous electrical volt-

age.

Note

Indicates notes that draw your attention to special features.

Note

Indicates cross-references to other documents, e.g. appli-

cation reports, operating manuals of combination elec-

trodes, etc.


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Safety Multi 720

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2.1 Authorized use

This instrument is authorized exclusively for measuring the

pH, Redox, dissolved oxygen and conductivity in the labora-tory.

The technical specifications as given in chapter 7 TECHNICAL

DATA, must be observed. Only the operation and running of

the measuring instrument according to the instructions given

in this operating manual is authorized.

Any other use is considered unauthorized.

2.2 General safety instructions

This instrument is constructed and tested in compliance withthe EN 61010-1 safety regulations for electronic measuring

instruments.

It left the factory in a safe and secure technical condition.

Function and opera-

tional safety

The smooth functioning and operational safety of the instru-

ment can only be guaranteed if the generally applicable

safety measures and the specific safety instructions in this

operating manual are followed.

The smooth functioning and operational safety of the instru-

ment can only be guaranteed under the climatic conditions

specified in chapter 7 TECHNICAL DATA.

If the instrument was transported from a cold environment to

a warm environment, the formation of condensate can lead

to the faulty functioning of the instrument. In this event, wait

until the temperature of the instrument reaches room tem-

perature before putting the instrument back into operation.

Caution

The instrument is only allowed to be opened by personnel

authorized by WTW.


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Multi 720 Safety

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Safe operation If safe operation is no longer possible, the instrument must

be taken out of service and secured against inadvertent op-

eration.Safe operation is no longer possible if:

l the instrument has been damaged in transport

l the instrument has been stored under adverse conditions

for a lengthy period of time

l the instrument is visibly damaged

l the instrument no longer operates as described in this

manual

If you are in doubt contact the supplier of the instrument.

Obligations of the

operator

The operator of this measuring instrument must ensure that

the following laws and guidelines are observed when using

dangerous substances:

l EEC directives for protective labor legislation

l

National protective labor legislationl Safety regulations

l Safety datasheets of the chemical manufacturer


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Safety Multi 720

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Multi 720 Commissioning

95

3 Commissioning

NoteYou can adapt individual parameters to your requirements.

To do so, change the default settings according to section

4.9 CONFIGURATION.

Connecting the

plug-in power

supply (optional)

The measuring instrument works battery-powered. It can,

however, also be supplied by the plug-in power supply

which is available as an accessory.

Warning

The line voltage on site must lie within the input voltage

range of the original plug-in power supply unit (see chapter

7 TECHNICAL DATA).

Caution

Use original plug-in power supplies only

(see chapter 7 TECHNICAL DATA).

Note

If a stirrer is operated via the measuring instrument, it is

essential to use the plug-in power supply.

1 Insert the plug (1) into the socket (2) of the meter.

2 Connect the original WTW plug-in power supply (3) to

an easily accessible mains socket.

1

2

3


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Commissioning Multi 720

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Scope of delivery l Laboratory measuring instrument, inoLab Multi 720

l Operating manual and short manual

l 4 x type AA Mignon 1.5 V batteries


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Multi 720 Operation

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4 Operation

4.1 Switch on the instrument

Note

The instrument has an energy saving feature to avoid un-

necessary battery depletion.

The energy saving feature switches the instrument off if no

key has been pressed for an hour.The energy saving feature is not active if the instrument is

supplied by the plug-in power supply.

1 Place the instrument on a flat surface and protect it

against intense light and heat.

2 Press thee key.The display testappears briefly on the display.

The instrument then switches automatically to the

measuring mode.

Probe connected Measuring mode

No probe or

pH/Redox electrode

pH or Redox measurement

(depending on the previously

selected measuring mode)

D. O. probe or conductivity

measuring cell

Previously selected measur-

ing mode

Any 2 probes Previously selected measur-

ing mode

Measuring mode

on switching on


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Operation Multi 720

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4.2 Measuring the pH value/Redox voltage

Preparatory

activities

Perform the following preparatory activities when you want

to measure:

Note

Incorrect calibration of the pH electrode will result in incor-

rect measured values. Therefore, regularly perform calibra-

tion before measuring.

Temperature probe Measurements can be performed with and without a temper-ature probe. A connected temperature probe is indicated by

TP on the display.

Note

If you use a pH electrode without a temperature probe, the

instrument is able to use the temperature probe of a D. O.

probe or conductivity measuring cell that is also connected

to the instrument and is immersed in the test sample. You

have to set up this as described in section 4.9 CONFIGURATI-

ON. The TP display indicator flashes when the temperature

probe of the D. O. probe or conductivity cell is used.

1 Press them key repeatedly until the pH/Redoxmeasurement appears on the display.

2 Connect the electrode to the instrument.

3 Adjust the temperature of the buffer or test solutions

or measure the current temperature if the measure-

ment is made without a temperature probe.

4 Calibrate or check the instrument with the electrode.

5 Select the measuring mode by pressingm.


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Multi 720 Operation

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The temperature measurement is absolutely essential for a

reproducible pH measurement. If the measurement is made

without a temperature probe, proceed as follows:

Note

When calibrating without a temperature probe, set up the

current temperature of the respective buffer solution manu-ally using the8 or2 keys while pressing and holdingdown theg key.

1 Determine the current temperature using a thermo-

meter.

2 Press and hold down theg key and set up the tem-perature using8 or2.


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Operation Multi 720

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4.2.1 Measuring the pH value

AutoRead AR

(Drift control)

The AutoReadfunction (drift control) checks the stability of

the measurement signal. The stability has a considerable ef-

fect on the reproducibility of the measured values.

For identical measurement conditions, the following criterionapplies:

l pH value: better than 0.02 (response time: > 30 s)

1 Perform the preparatory activities according to sec-

tion 4.2.

2 Immerse the pH electrode into the test sample.

3 Press the8 or2 key until pHappears in the statusdisplay. The pH value appears on the display.

1 Call up the pH measuring mode by pressing82.

2 Immerse the pH electrode into the test sample.

3 Activate the AutoRead function by pressinga.The current measured value is frozen (Hold function).

4 Start the AutoRead function by pressingg.AR flashes on the display until a stable measured val-

ue is reached.

5 If necessary, start the next AutoRead measurement

by pressingg.

6 To terminate the AutoRead function: Pressa.


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Multi 720 Operation

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Note

The current AutoRead measurement (with acceptance of

the current value) can be terminated at any time by pressingg. It is only possible to change to another measuring modeafter AutoRead has been terminated.

4.2.2 Measuring the Redox voltage

The instrument can measure the Redox voltage (mV) of a

solution when connected with a Redox electrode, e.g.

SenTix ORP.

Note

The AutoRange function is always active and automatically

switches to the measuring range with the highest resolution.

Note

Redox electrodes are not calibrated. However, you can

check Redox electrodes using a test solution.


tion 4.2.

2 Immerse the Redox electrode into the test sample.

3 Press the82 key repeatedly until U appears inthe status line.

The Redox voltage (mV) of the sample appears on

the display.

4 Wait for a stable measured value.


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Operation Multi 720

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4.3 Calibrating for pH measurements

Why calibrate? pH electrodes age. This changes the asymmetry (zero

point) and slope of the pH electrode. As a result, an inexactmeasured value is displayed. Calibration determines the

current values of the asymmetry and slope of the electrode

and they are stored in the instrument.

Thus, you should calibrate at regular intervals.

Note

Always calibrate after connecting another pH electrode.

You can choose between 3 calibration procedures:

AutoCal TEC is specially adapted to the WTW technical buffer solutions

as a fully automatic two-point calibration. The buffer solu-

tions are automatically recognized by the instrument.

AutoCal DIN is specially adapted to permanently programmed buffer so-

lutions according to DIN 19266 as a fully automatic two-

point calibration. The buffer solutions are automatically rec-

ognized by the instrument.

ConCal is the conventional two-point calibration with 2 freelyselectable buffer solutions or single-point calibration as the

rapid method.

AutoRead In calibration using AutoCal TEC and AutoCal DIN, the Au-

toReadfunction is automatically activated.


the current value) can be terminated at any time by pressingg.

Calibration

evaluation

After the calibration, the instrument automatically evaluates

the current status. The asymmetry and slope are separately

evaluated. The worst evaluation appears on the display.


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Multi 720 Operation

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.

Display Asymmetry

[mV]

Slope

[mV/pH]- 15 ... +15 -60.5 ... -58

-20 ... +20 -58 ... -57

-25 ... +25 -61 ... -60.5

or-57 ... -56

Clean the electrode accord-

ing to the electrode manual

-30 ... +30 -62 ... -61

or

-56 ... -50

E3

Clear the fault according to

chapter 6 WHATTODOIF...

< -30 or> 30

< -62 or> -50

1 Switch on the instrument by pressinge.

2 Press them key repeatedly until the pH/Redoxmeasurement appears on the display.

3 Connect the pH electrode to the instrument.

4 Keep the buffer solutions ready.

5 Adjust the temperature of the solutions and measure

the current temperature if the measurement is per-

formed without a temperature probe.

Preparatory

activities


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Operation Multi 720

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4.3.1 AutoCal TEC

Use any two of the WTW technical buffer solutions for this

procedure (pH 2.00, 4.01, 7.00, or 10.01).

Note

The calibration for pH 10.01 is optimized for the WTW tech-

nical buffer solution TEP 10 Trace or TPL 10 Trace. Other

buffer solutions can lead to an erroneous calibration. The

correct buffer solutions are given in the WTW catalog or in

the Internet.

Note

Steps 2 and 6 are not required if you use a temperatureprobe.

1 Press thec key repeatedly until the AutoCal TECfunction display appears.

2 If necessary, set the temperature of the buffer solu-

tion by pressing82.

3 Submerse the pH electrode in the first buffer solution.

4 Press theg key.AR flashes on the display.The electrode voltage (mV) appears on the display.

As soon as a stable value is recognized, Ct2 ap-

pears.


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Multi 720 Operation

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Note

If the slope (SLO) is indicated on the display, you can

change the unit of the slope with82.The display in % refers to the Nernst slope, 59.2 mV/pH

(100 x the slope determined/Nernst slope).

5 Thoroughly rinse the electrode with distilled water.

6 If necessary, set the temperature of the second buffer

solution by pressing82.

7 Submerse the electrode in the second buffer solution

8 Press theg key.AR flashes on the display.

The electrode voltage (mV) appears on the display.

As soon as a stable value is recognized, AR disap-

pears.

The probe symbol shows the electrode evaluation af-

ter the two-point calibration.The value of the slope (mV/pH) appears on the dis-

play.

9 Press theg key.The value of the asymmetry (mV) appears on the dis-

play.

10 To return to the measuring mode: Press them keyor continue with three-point calibration.


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Operation Multi 720

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4.3.2 AutoCal DIN

Use two different DIN buffer solutions (type A, C, D or F with

the pH values 1.679, 4.006, 6.865, 9.180) for this procedure.

Note

Steps 2 and 6 are not required if you use a temperature

probe.

1 Press thec key repeatedly until the AutoCal DINfunction display appears.


tion by pressing82.

3 Submerse the pH electrode in the first buffer solution.



As soon as a stable value is recognized, Cd2 ap-

pears.



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Multi 720 Operation

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Note


change the unit of the slope with82.The display in % refers to the Nernst slope, 59.2 mV/pH

(100 x the slope determined/Nernst slope).

6 If necessary, set the temperature of the second buffer

solution by pressing82.

7 Submerse the electrode in the second buffer solution.



As soon as a stable value is recognized, AR disap-

pears.

The sensor symbol shows the electrode evaluation

after the two-point calibration.

The value of the slope (mV/pH) appears on the dis-play.


play.

10 To return to the measuring mode: Press them keyor continue with three-point calibration.


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Operation Multi 720

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4.3.3 ConCal

Two-point

calibration

Use two buffer solutions for this procedure:

l pH 7.0 0.5

l any other buffer solution

Note

Steps 2 and 6 are not required if you use a temperature

probe.

1 Press thec key repeatedly until the ConCal func-tion display appears.


tion by pressing82.

3 Submerse the pH electrode in the pH 7.0 0.5 buffer

solution.

4 Press theg key.The measured pH value appears on the display.

5 Set the nominal pH value of the buffer solution (at the

current temperature) by pressing the82 keys.6 Press theg key.

The value of the asymmetry (mV) and the sensor

symbol appear on the display.

7 Press theg key.SLO(pe) appears on the display.


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Multi 720 Operation

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Note


change the unit of the slope with82.

The display in % refers to the Nernst slope, 59.2 mV/pH(100 x the slope determined/Nernst slope).


9 If necessary, set the temperature of the second buffersolution by pressing82.

10 Submerse the electrode in the second buffer solution.

11 Press theg key.The second measured pH value appears on the dis-

play.

12 Set the nominal pH value of the second buffer solu-

tion (at the current temperature).

13 Press theg key.The value of the slope (mV/pH) appears on the dis-

play.

The sensor symbol shows the evaluation of the elec-

trode after the two-point calibration.


play.

15 To return to the measuring mode: Press them key.


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Operation Multi 720

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Single-point

calibration

Use any buffer solution for this rapid method. The calibration

will be the more exact the nearer the pH value of the buffer

solution is to that of the test sample.

Note

Only the electrode asymmetry is determined in single-point

calibration. The slope of the last two-point calibration is re-

tained.

Note

Step 2 is not required if you use a temperature probe. The

TP display indicates an active temperature measurement.

1 Press thec key repeatedly until the ConCalfunction display appears.

2 Set the temperature of the buffer solution by pressing

82.

3 Submerse the pH electrode in the buffer solution.

4 Press theg key.The measured pH value appears on the display.

5 Set the nominal pH value of the buffer solution (at the

current temperature) by pressing the82 keys.

6 Press theg key.The value of the asymmetry (mV) and the sensor

symbol for the evaluation of the electrode appears on

the display.

7 To return to the measuring mode: Press them key.


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Multi 720 Operation

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4.4 Measuring the dissolved oxygen

The following parameters can be measured:

l Oxygen concentration

l Oxygen saturation

l Oxygen partial pressure

The measuring instrument has the following functions:

l AutoRange (automatic selection of the measuring range),

l AutoRead (drift control) to check the stability of the mea-

suring signal. This ensures the reproducibility of the mea-

suring signal. How to switch the AutoRead function on/off

see page 114.

Preparatory

activities


to measure:

Note

Incorrect calibration of the D. O. probe will result in incorrectmeasured values. Therefore, regularly perform a calibration.

Temperature probe The D. O. probe has an integrated temperature probe that

always measures the current temperature of the test sam-

ple.

1 Connect the D. O. probe to the measuring instru-

ment. The instrument recognizes the probe and auto-

matically switches to the previously selected oxygenmeasuring mode. If the D. O. probe is already con-

nected, press them key repeatedly until the oxygenmeasuring mode appears.

2 Calibrate or check the measuring instrument with the

probe. The calibration is described in section 4.5 from

page 116.


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Operation Multi 720

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4.4.1 Oxygen concentration

When measuring the concentration in test samples with a

salt content of more than 1 g/l, a salinity correction is re-

quired.

Note

How to enter the current salt content is described in section

4.5.2 on page 120. How to switch the salinity correction on/

off see below.

When you want to measure the oxygen concentration

without salinity correction, proceed as follows:

Switching the

salinity correction

function on/off

To switch the salinity correction on, proceed as follows:


tion 4.2.

2 Immerse the D. O. probe into the test sample.

3 Press the82 key until the oxygen concentrationin mg/lappears on the display.

1 Press and hold down theg key and with8 switchon the salinity correction function.Salappears on the display. The salt content set up is

taken into account for the measurement.


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Multi 720 Operation

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4.4.2 Oxygen saturation

To measure the oxygen saturation proceed as follows:

2 Press and hold down theg key and with2 switchoff the salinity correction function.

Saldisappears from the display.


tion 4.4.


3 Press the82 key until the oxygen saturation in %appears on the display.


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Operation Multi 720

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4.4.3 Oxygen partial pressure

To measure the oxygen partial pressure proceed as follows:

Note

The AutoRange function is always active and automatically

switches to the measuring range with the highest resolution.

4.4.4 AutoRead AR (drift control)


the measured signal. The stability has a considerable influ-

ence on the reproducibility of the measured value.


tion 4.4.


3 Press the82 key until the oxygen partial pressurein mbarappears on the display.

1 Call up the measuring mode usingm and/or82.


3 Activate the AutoRead function usinga. The cur-rent measured value is frozen (hold function).

4 Start AutoRead by pressingg.ARflashes until a stable measured value is reached.


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Multi 720 Operation

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Note


the current value) can be terminated at any time by pressing

g. It is only possible to change to another measuring modeafter AutoRead has been terminated.

Criteria For identical measuring conditions, the following applies:


by pressingg.

6 To terminate the AutoRead function: Pressa.

Parameter Reproducibility Response time

Oxygen

concentration

better 0.05 mg/l > 10 seconds

Oxygen satura-

tion

better 0.6 % > 10 seconds

Oxygen partial

pressure

better 0.6 mbar > 10 seconds


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Operation Multi 720

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4.5 Calibrating for D. O. measurements

Why calibrate? D. O. probes age. This changes the slope of the probes. As

a result, an inexact measured value is displayed. Calibrationdetermines the current slope of the probe and stores it in the

instrument.

When to calibrate? l At regular intervals (every 2 weeks)

l After connecting another D. O. probe

Calibration

procedure

Calibration is made in water vapour saturated air. Use the

OxiCal-SL air calibration vessel (accessory) for calibration.

AutoRead The AutoReadfunction is automatically activated during cal-

ibration. AR flashes on the display. The calibration process

is finished when AR stops flashing.


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Operation Multi 720

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4.5.1 Starting the calibration

To calibrate the instrument proceed as follows:

Note

The sponge in the air calibration vessel must be moist (not

wet). Observe the instructions in the OxiCal-SL manual.

1 Connect the D. O. probe to the instrument.

2 Keep the OxiCal-SL air calibration vessel ready.

3 Put the D. O. probe into the air calibration vessel.

4 Press thec key repeatedly until the calibrationmode appears.

5 Press theg key. AutoRead is activated, ARflashes.


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Multi 720 Operation

119

Note

Refer to chapter 6 WHATTODOIF... for error elimination.

6 As soon as a stable value is reached, ARstops flash-

ing. Thus the calibration is finished and the probesymbol indicates the relative slope determined and

the probe evaluation (see page 117).

7 Withm change to the measuring mode.


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Operation Multi 720

120

4.5.2 Entering the salt content (salinity)

When measuring the concentration of test samples with a

salt content of more than 1 g/l, a salinity correction is re-

quired. For this, you have to determine and input the salinity

of the test sample first. Before measuring, switch on the sa-

linity correction.

NoteHow to switch on the salinity correction is described on

page 112.

Parameter Value range

Salinity 0.0 ... 70.0 in 0.1 steps

1 Determine the salinity of the test sample (any meth-

od; see also section 4.6.2 on page 124).

2 Press thec key repeatedly until Salappears on thedisplay.

3 With82 enter the salt content.

4 Withm change to the measuring mode.

Input


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Multi 720 Operation

121

4.6 Measuring the conductivity

The following parameters can be measured:

l Conductivity/resistance

(how to switch over, see section 4.9 CONFIGURATION)

l Salinity

l Total dissolved solids (TDS)

The measuring instrument has the following functions:

l AutoRange (automatic selection of the measuring range),

l AutoRead (drift control) to check the stability of the mea-suring signal. This ensures the reproducibility of the mea-

suring signal. How to switch the AutoRead function on/off

see page 126.

Preparatory

activities


to measure:

1 Connect the conductivity measuring cell withtemperature probe to the measuring instrument. The

instrument recognizes the measuring cell and

automatically switches to the previously selected

conductivity measuring mode. If the conductivity cell

is already connected, press them key repeatedlyuntil the conductivity measuring mode appears.

2 Check the cell constant set up or calibrate the

measuring instrument with the measuring cell. The

calibration is described in section 4.7.1 DETERMININGTHECELLCONSTANT (CALIBRATIONINCONTROL

STANDARD) from page 127 on.


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Operation Multi 720

122

Note

An incorrect cell constant will result in incorrect measured

values. Therefore, regularly check the cell constant set up

and calibrate at regular intervals.

Checking the cell

constant3 Press thec key repeatedly until LF CELL is

displayed.

4 Press theg key. The previously selected cellconstant ist displayed, e. g. 0.475 cm-1.

5 To return to the measuring mode: press them keywhen the correct cell constant ist displayed.

6 If a different cell constant is to be set, proceed

according to section SECTION 4.7 DETERMINING/

SETTINGUPTHECELLCONSTANT [C].


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Multi 720 Operation

123

Temperature probe The conductivity measuring cell has an integrated tempera-

ture probe that always measures the current temperature of

the test sample.

If you want to use a WTW conductivity measuring cell with-

out a temperature probe, you have to connect it with an

adapter (available at WTW).

4.6.1 Conductivity / Specific resistance

NoteYou can display measured values in the units S/cm (con-

ductivity) or Mcm (specific resistance). This setting is de-

scribed in Abschnitt 4.9 CONFIGURATION.

Thus, you can carry out conductivity measurements or mea-

surements of the specific resistance:

Conductivity

1 Perform the preparatory activities according to

section 4.6.

2 Immerse the conductivity measuring cell into the test

sample.

3 Press them key until appears in the statusdisplay. Depending on the setting, one of the

following display indicators appears on the display:


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Operation Multi 720

124

Specific resistance

4.6.2 Salinity

To measure the salinity, proceed as follows:



section 4.6.


sample.

3 Press the82 key repeatedly until Salappears inthe status line.

The salinity value of the sample appears on the

display.



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Multi 720 Operation

125

4.6.3 TDS (total dissolved solids)

To measure the TDS, proceed as follows:

:

Note

Also refer to Application Report ... 084 KONDUCTOMETRICAL

DETERMINATIONOFTHE TOTAL DISSOLVED SOLIDS (TDS).


section 4.6.

2 Immerse the conductivity cell into the test sample.

3 Press the82 key repeatedly until TDSappearsin the status line. The TDS value of the sample

appears on the display.

4 Press and hold down theg and set up the TDSfactor (0.40 ... 1.00) using82.



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Operation Multi 720

126

4.6.4 AutoRead AR (Drift control)


the measurement signal. The stability has a considerable ef-

fect on the reproducibility of the measured values.

Note


the current value) can be terminated at any time by pressing

g. It is only possible to change to another measuring modeafter AutoRead has been terminated.

1 Call up the required measuring mode by pressing

82.


sample.

3 Activate the AutoRead function by pressinga.

The current measured value is frozen (Hold function).

4 Start the AutoRead function by pressingg.AR flashes on the display until a stable measured

value is reached.


by pressingg.

6 To terminate the AutoRead function: Press theakey.


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Multi 720 Operation

127

4.7 Determining/setting up the cell constant [C]

Why determine/set

up the cell con-stant?

Due to ageing, the cell constant slightly changes. As a re-

sult, an inexact measured value is displayed. Calibration de-termines the current value of the cell constant and stores

this value in the instrument.

Thus, you should calibrate at regular intervals (recommend-

ed interval: every 6 months).

You can determine the cell constant of the conductivity mea-

suring cell in the range 0.450 ... 0.500 cm-1 or

0.800 ... 1.200 cm-1 by calibrating in the control standard or

set it up manually in the range 0.250... 2.500 cm-1

. Addition-ally, you can select the fixed cell constants 0.100 cm-1 or

0.010 cm-1.

4.7.1 Determining the cell constant

(calibration in control standard)

Determine the cell constant as follows:

1 Press thec key repeatedly until LF CELL appearson the display.

2 Press theg key.

3 Press thec key repeatedly until the following isdisplayed:


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Operation Multi 720

128

Note

l This method of automatically determining the cell con-

stant by calibrating in the 0.01 mol/l KCL control standard

can only be used for measuring cells with a cell constant

in the range 0.450 ... 0.500 cm-1 or 0.800 ... 1.200 cm-1.

l If message E3 appears see chapter 6 WHATTODOIF...

4 Immerse the measuring cell into the 0.010 mol/l KCL

control standard.

5 Press thegkey to start the AR measurement todetermine the cell constant. The AR flashes on the

display until a stable signal is reached. The

determined cell constant ist displayed. The

measuring instrument automatically stores the cell

constant.

6 To return to the measuring mode: pressgorm.


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Multi 720 Operation

129

Calibration

evaluation

After calibrating, the instrument automatically evaluates the

current condition of the calibration.

The evaluation appears on the display.

Display Cell constant [cm-1]

0.450 ... 0.500 cm-1

0.800 ... 1.200 cm-1

E3

Perform error elimination

according to chapter 6

WHATTODOIF...

outside of the ranges

0.450 ... 0.500 cm-1

or

0.800 ... 1.200 cm-1


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Operation Multi 720

130

4.7.2 Setting up the cell constant

Setting up the cell

constant manually

To set up the cell constant manually, proceed as follows:

Note

The cell constant to be set up must either be taken from the

operating manual of the measuring cell or is printed on the

measuring cell.

1 Press the

ckey repeatedly until LF CELL appears

on the display.

2 Press theg key.

3 Press thec key repeatedly until the followingdisplay appears:

4 Set up the cell constant to be used by pressing

82, e. g. 0.614 cm-1.


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Multi 720 Operation

131

Selecting the

0.100 cm-1

cell constant

To select the 0.100 cm-1 cell constant proceed as follows:

5 To return to the measuring mode: press them key.


2 Press theg key to go to the "Determining/setting upthe cell constant" function.

3 Press thec key repeatedly until the 0.100 cm-1 cellconstant appears on the display.



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Operation Multi 720

132

Selecting the

0.010 cm-1

cell constant

To select the 0.010 cm-1 cell constant proceed as follows:


2 Press theg key.

3 Press thec key repeatedly until the 0.0100 cm-1cell constant appears on the display.



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Multi 720 Operation

133

4.8 Setting up the temperature compensation TC

The calculation of the temperature compensation is based

on the preset reference temperature, Tref 20 or Tref 25 (seesection 4.9 CONFIGURATION).

You can select one of the following temperature compensa-

tions:

l Non-linear temperature compensation "nLF"

according to DIN 38404 or EN 27 888

l linear temperature compensation"Lin" with a coeffi-

cient that can be set in the range 0.001 ... 3.000 %/Kl no temperature compensation

Note

ips Select the following temperature compensations to work

with the test samples given in the table:

Application

notesTest sample Temperature

compensation TC

Display

indicator

Natural water

(ground water,

surface water,

drinking water)

nLF

according to DIN 38404

EN 27 888

Ultrapure water nLF

according to DIN 38404

EN 27 888

Other aqueous

solutions

Set linear

temperature coefficient0.001 ... 3.000 %/K

Salinity

(seawater)

Automatically nLF

according to IOT

Sal,


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Operation Multi 720

134

Selecting the non-

linear temperature

compensation

To select the non-linear temperature compensation proceed

as follows:

1 Press thec key repeatedly until LF tcappears onthe display.

2 Press theg key.

3 Press thec key repeatedly until nLFappears on thedisplay.



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Multi 720 Operation

135

Selecting the linear

temperature com-

pensation

To select the linear temperature compensation proceed as

follows:

1 Press thec key repeatedly until LF tcappears onthe display.

2 Press theg key.

3 Press thec key repeatedly until the adjustablelinear temperature coefficient appears on the display.

4 Set up the temperature coefficient, e. g. 1.880 %/K

using82.



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Operation Multi 720

136

Switching off the

temperature com-

pensation

To switch off the temp. compensation proceed as follows:

1 Press thec key repeatedly until LF tcis displayed.

2 Press theg key.

3 Press thec key until the following display appears:

4 The temperature compensation is switched off.


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Multi 720 Operation

137

4.9 Configuration

You can adapt the measuring instrument to your individual

requirements. To do this, the following parameters can bechanged (the status on delivery is marked in bold):

NoteYou can leave the configuration menu at any time. Parame-

ters that have already been changed are stored.

To do this, press them key.

Temperature probe that is used

for the pH measurement

pH temperature probe,

LF/O2 temperature

probe

Air pressure display Current value in mbar

(only if a D. O. probe is

connected - no inputpossible)

Reference temperature 20 C, 25 C

Representation of the measured

value as conductivity or resis-

tance

Conductivity,

resistance

Temperature unit C, F

1 Switch off the instrument.

2 Press and hold down them key.

3 Press thee key.The display testappears briefly on the display.

The instrument then switches automatically to the

setting of the temperature probe for the pH

measurement.


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Operation Multi 720

138

4 Set up pH TP or LF-O2 TP by pressing82.

5 Confirm withg. Pappears on the display and, if aD. O. probe is connected, the current air pressure in

mbar.

6 Confirm withg. t25or t20appears on the display.

7 With82 select between t25 and t20.

8 Confirm withg.LFappears on the display.

Temperature probe

Air pressure

Reference

temperature


57/82

Multi 720 Operation

139

9 With82 select betweenS/cm and M.

10 Confirm withg.USEappears on the display.

11 With82 select betweenCand F.

12 Confirm withg. The instrument automaticallychanges to the previously selected measuring mode.

Conductivity or

resistancemeasurement

Temperature unit


58/82

Operation Multi 720

140

4.10 Reset

Basic settings You can reset (initialize) the settings for the pH, oxygen and

conductivity measurement separately.

pH measurement The following functions for the pH measurement (pH InI) are

reset to the values they had on delivery:

Oxygen measure-

ment

The following functions for the oxygen measurement (O2

InI) are reset to the values they had on delivery:

Conductivity mea-

surement

The following functions for the conductivity measurement

( InI) are reset to the values they had on delivery:

Measuring mode pH

Asymmetry 0 mV

Slope -59.16 mV/pH

Calibration procedure AutoCal TECTemperature, manual 25 C

Measuring mode Oxygen concentration

Relative slope 1.00

Salinity (value) 0.0Salinity (function) off

Measuring mode

Cell constant 0.475 cm-1 (calibrated)

0.475 cm-1 (set up)

Temperature compensation nLF

Reference temperature

Temperature coefficient of

the linear temperature com-

pensation

2.000 %/K

TDS factor 1.00


59/82

Multi 720 Operation

141

Note

After a reset, the calibration data are lost. Thus, calibrate af-

ter a reset.

Proceed as follows to reset the settings:

1 Press and hold down theg key.

2 Press thec key.

3 Toggle between no and yes by pressing82.yes: reset the settings for pH.

no: retain settings.

4 Confirm withg. The instrument changesautomatically to the settings for the oxygen

measurement.

5 Toggle between no and yes by pressing82.yes: reset the settings for oxygen.


Resetting the pH

settings

Resetting the oxy-

gen settings


60/82

Operation Multi 720

142

6 Confirm withg. The instrument changes to thesettings for the conductivity measurement.

7 Toggle between no and yes by pressing82.yes: reset the settings for conductivity.


8 Confirm withg.The instrument changes automatically to the

previously selected measuring mode.

Resetting the con-

ductivity settings


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Multi 720 Maintenance, cleaning, disposal

143

5 Maintenance, cleaning, disposal

5.1 MaintenanceThe measuring instrument is almost maintenance-free. The

only maintenance task is replacing the batteries:

Caution

Make sure that the poles of the batteries are the right way

round.The signs in the battery compartment must correspond to

the signs on the batteries.

Only use leakproof alkaline manganese batteries.

Note

See the relevant operating manual of the probes and

electrodes for instructions on maintenance.

1 Open the battery compartment (1) on the underside

of the instrument.

2 Remove the four batteries from the battery

compartment.

3 Insert four new batteries (Type Mignon AA) into the

battery compartment.

4 Close the battery compartment (1).

1


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Maintenance, cleaning, disposal Multi 720

144

5.2 Cleaning

Occasionally wipe the outside of the measuring instrument

with a damp, lint-free cloth. Disinfect the housing withisopropanol as required.

Caution

The housing is made of synthetic material (ABS). Thus,

avoid contact with acetone or similar detergents that contain

solvents. Remove any splashes immediately.

5.3 Disposal

Packing The measuring instrument is sent out in a protective

transport packing.

We recommend: Keep the packing material. The original

packing protects the instrument against damage during

transport.

Batteries This note refers to the battery regulation that applies in theFederal Republic of Germany. We would ask end-

consumers in other countries to follow their local statutory

provisions.

Note

In compliance with 14 of the BATTERY REGULATION, we

would like to point out that this instrument contains batteries.

Batteries that have been removed must only be disposed of

at the recycling facility set up for this purpose or via the retail

outlet.

It is illegal to dispose of them in household refuse.

Measuring

instrument

Dispose of the measuring instrument as electronic waste at

an appropriate collection point. It is illegal to dispose of them

in household refuse.


63/82

Multi 720 What to do if...

145

6 What to do if...

6.1 pH system messages

Cause Remedy

pH electrode:

Not connected Connect electrode

Air bubbles in front of the

diaphragm

Remove air bubbles

Air in the diaphragm Extract air or

moisten diaphragm

Cable broken Replace electrode

Gel electrolyte dried out Replace electrode

Cause Remedy

pH electrode:

Diaphragm contaminated Clean diaphragm Membrane contaminated Clean membrane

Moisture in the plug Dry plug

Electrolyte obsolete Replenish electrolyte or

replace electrode

Electrode obsolete Replace electrode

Electrode broken Replace electrode

Measuring instrument:

Incorrect calibration

procedure

Select correct

procedure

Incorrect solution

temperature (without

temperature probe)

Set up correct

temperature

Socket damp Dry socket

Error message,

OFLOFLOFLOFL

Error message,

E3E3E3E3


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What to do if... Multi 720

146

Buffer solutions:

Incorrect buffer solutions Change calibrationprocedure

Buffer solutions too old Only use once.

Note the shelf life

Buffer solutions depleted Change solutions

Cause Remedy

pH electrode:

Diaphragm contaminated Clean diaphragm

Membrane contaminated Clean membrane

Sample:

pH value not stable Measure with air

excluded if necessary

Temperature not stable Adjust temperature if

necessary

Electrode + sample:

Conductivity too low Use suitable electrode

Temperature too high Use suitable electrode

Organic liquids Use suitable electrode

No stable

measured value


65/82


147

6.2 Oxygen system messages

Cause Remedy

pH electrode:

pH electrode unsuitable Use suitable electrode

Temperature difference

between buffer and

sample too large

Adjust temperature of

buffers or samples

Measuring procedure not

suitable

Follow special procedure

Cause Remedy

Display range exceeded

D. O. probe:

Not connected Connect D. O. probe

Depleted Replace D. O. probe

Cable broken Replace D. O. probe

Short circuit between gold

and lead electrode

Clean D. O. probe, if

necessary exchange it

Cause Remedy

Invalid calibrationD. O. probe:

Electrolyte depleted Regenerate D. O. probe


Electrode system poisoned Regenerate D. O. probe

obsolete Replace D. O. probe

broken Replace D. O. probe

Obviously incorrect

measured values

Error message,

OFLOFLOFLOFL

Error message,

E3E3E3E3


66/82


148

Cause Remedy

Damaged membrane

Membrane damaged Regenerate D. O. probe

Membrane head not tight

enough

Screw membrane head

tight

Cause Remedy

No stable measured value


Cause Remedy

Insufficient flow Provide flow to the

probe

Cause Remedy

High amount of dissolved

substances

Correct solubility

function using the

salinity equivalent

Air bubbles bump on the

membrane with high

velocity

Avoid direct flow to the

membrane

The carbon dioxidepressure is too high -

> 1 bar

Measuring not possible

Error message,

E7E7E7E7

AR flashes for a

longer time

Measured values too

low

Measured values too

high


67/82


149

6.3 Conductivity system messages

6.4 General errors

You would like to

know which soft-

ware version is in

the instrument

Cause Remedy

The measured value is out-

side the measuring range

Measuring cell not

connected

Connect measuring

cell

Cable broken Replace electrode

Cause Remedy Measuring cell

contaminated

Clean measuring cell;

if necessary, replace it

Unsuitable calibration

solution

Check calibration

solutions

Cause Remedy

Batteries almost

depleted

Replace batteries

(see section

5.1 MAINTENANCE)

Cause Remedy

Operating stateundefined or EMC

electric stress unallowed

Processor reset:Press thea key andswitch on instrument

Error message,OFLOFLOFLOFL

Error message,E3E3E3E3

LoBat

Instrument does not

react to keystroke

Ursache Behebung

e.g. question of the WTW

service department

Press thea key andswitch on instrument.

The software version

is displayed.


68/82


150


69/82

Multi 720 Technical Data

151

7 Technical Data

7.1 General data

Storage temperature - 25 C ... + 65 C

Operating temperature 0 C ... + 55 C

Allowable relative

humidity

Annual mean: < 75 %

30 days/year: 95 %

Other days: 85 %

Length [mm] 230

Width [mm] 210

Height [mm] 70

Weight [kg] Approx. 0.850

EMC E.C. guideline 89/336/EEC

EN 61326-1:1997

EN 61000-3-2 A14:2000EN 61000-3-3:1995

FCC Class A

Instrument safety E.C. guideline 73/23/EEC

Protective class 3, EN 61010-1 A2:1995

Climatic class 2, VDI/VDE 3540

Ambient

temperature

Dimensions and

weight

Guidelines

and norms used


70/82

Technical Data Multi 720

152

UL/CUL, CE

Batteries 4 x 1.5 V AA type alkaline manganese

batteries

Runtime Approx. 3000 operating hours

Mains power

supply (option)

Connection max. overvoltage category

II (valid for all plug-in power supplies):

Plug-in power supply unit

(Euro, US, UK, Australian plug)

FRIWO FW7555M/09, 15.1432

Friwo Part. No. 1822089

Input:

100 ... 240 V ~ / 50 ... 60 Hz / 400 mA

Output: 9 V = / 1,5 A

Plug-in power supply (Euro plug):FRIWO FW1199, 11.7864

Friwo Part. No. 1762613

Input: 230 V ~ / 50 Hz / 5.6 VA

Output: 12 V = / 130 mA / 1.56 VA

Plug-in power supply (UK plug):

FRIWO FW3288, 11.8453

Friwo Part No. 1816491

Input: 230V ~ / 50 Hz / 23 VA

Output: 6 V = / 1,8 A

FCC Class A Equipment Statement

Note: This equipment has been tested and found to comply withthe limits for a Class A digital device, pursuant to Part 15 of theFCC Rules. These limits are designed to provide reasonableprotection against harmful interference when the equipment isoperated in a commercial environment. This equipment

generates, uses, and can radiate radio frequency energy and, ifnot installed and used in accordance with the instruction manual,may cause harmful interference to radio communications.Operation of this equipment in a residential area is likely to causeharmful interference in which case the user will be required to

correct the interference at his own expense.

Test marks

Energy supply


71/82


153

7.2 pH/Redox measurement

pH - 2.00 ... + 16.00

U [mV] - 199.9 ... + 199.9

- 1999 ... + 1999

T [C] - 5.0 ... + 105.0

T [F] + 23.0 ... + 221.0

pH

(after calibration)

0.01

U [mV] 0.3 (at + 15 C ... + 35 C)

1

T [C] 0.1

T [F] 0.2

Manually [C] - 5 ... + 100

Measuring rangesand resolution

Accuracy

( 1 digit)

Temperature

input


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154

7.3 Oxygen measurement

mg/l % mbar

Range I

Resolution

0 ... 19.99

0.01

0 ... 199.9

0.1

0 ... 199.9

0.1

Range II

Resolution

0 ... 90.0

0.1

0 ... 600

1

0 ... 1250

1

T [C] 0.0 ... 50.0

T [F] +32.0 ... + 122.0

mg/l

Concentration

0.5 % of the measured value

at ambient temperature 5 C ... 30 C

%

Saturation

0.5 % of the measured value

when measuring in the range of

10 K around the calibration temperature

mbarPartial pressure 0.5 % of the measured valueat ambient temperature

5 C ... 30 C

Temperature

compensation

< 2 % at 0 ... 40 C

T [C] 0.1

T [F] 0.2

Salinity correc-

tion

0.0 ... 70.0 SAL

Air pressure

correction

automatic with integated pressure

sensor in the range

500 ... 1100 mbar


Accuracy

( 1 digit)

Correction functions


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155

7.4 Conductivity measurement

[S/cm]

[mS/cm]

0.000 ... 1.999(only with 0.010 cm-1 cell constant )

0.00 ... 19.99

(only with 0.010 cm-1 constant and

cell constant 0.100 cm-1)

0.0 ... 199.9

0 ... 1999

0.00 ... 19.99

0.0 ... 199.90 ... 500

Spec. resistance

[M*cm]

0.000 ... 1.999

0.00 ... 19.99

0.0 ... 199.9

0 ... 1999

SAL 0.0 ... 70.0 according to the IOT table

TDS [mg/l] 0 ... 1999

Factor can be set in the range0.40 ... 1.00

T [C] 5.0 ... + 105.0

T [F] + 23.0 ... + 221.0



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156

No compensation:

Accuracy 0.5 %

Non-linear compensation :

Accuracy Test sample temperature

0.5 % 0 C ... 35 C

according to EN 27 888;

0.5 % 35 C ... 50 C

extended

nLF function according to

WTW measurements

Linear compensation :


0.5 % 10 C ... 75 C

(the accuracy percentage always refers

to the measured value!)

SAL Range 0.0 ... 42.0


0.1 at 5 C ... 25 C

0.2 at 25 C ... 30 C

TDS [mg/l] 1

T [C] 0.1

T [F] 0.2

C [cm-1] 0.010

0.100

0.250 ... 2.500

C [cm-1] 0.450 ... 0.500

0.800 ... 1.200

TREF [C] 20

25

Accuracy

( 1 digit)

Cell constant,

to be set

Cell constant,

calibrated

Reference tempera-

ture, selectable


75/82

Multi 720 Lists

157

8 Lists

This chapter provides additional information and orientationaids.

Abbreviations The list of abbreviations explains abbreviations that appear

on the display or when dealing with the instrument.

Specialist terms The glossary briefly explains the meaning of the specialistterms. However, terms that should already be familiar to the

target group are not described here.

Index The index helps you find the topics that you are looking for.


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Lists Multi 720

158

Abbreviations

Conductivity value

ABS Plastic housing

AR AutoRead (drift control)

ARng Automatic range switching

Measuring instrument measures with high-

est resolution

ASY Asymmetry

AutoCal DIN Automatic calibration with DIN buffer solu-

tions

AutoCal TEC Automatic calibration with WTW technical

buffer solutions

C Cell constant cm-1

C Temperature unit, Celsius

Cal Calibration

Cd... Calibration with

DIN buffer solutions (acc. to DIN 19266)

CELL Cell constant

ConCal Conventional one/two point calibration

Ct... Calibration with WTW technical buffer so-

lutions

D. O. probe Dissolved oxygen probe

E3 Error message (see WHATTODOIF ...)

F Temperature unit, Fahrenheit

InI Initialization

Resets individual basic functions to

the status they had on delivery

Lin Linear temperature compensation


77/82

Multi 720 Lists

159

LoBat Low Battery

Batteries are almost empty

mV Voltage unit

mV/pH Unit of the electrode slope

nLF Non linear temperature compensation

OFL Overflow

Display range exceeded

Oxical Automatic calibration

pH pH valueS Slope

Sal Salinity

SELV Safety Extra Low Voltage

SLO Slope

Slope setting on calibration

TC Temperature coefficient

TDS Total dissolved solids

TP Temperature probe

Temperature measurement active

Tref 20/T20 Reference temperature 20 C

Tref 25/T25 Reference temperature 25 C

UASY Asymmetry potential


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Lists Multi 720

160

Glossary

Asymmetry Zero point of a pH electrode.

AutoRange Automatic selection of the measuring range.

AutoRead Monitors the electrode drift and releases the measured val-

ue only after the stability criterion has been reached. In this

way, this procedure ensures the highest degree of precision

and reproducibility.

Buffer solution Stable solution with a precisely known pH value.

Calibration The cell constant is determined through calibration. To do

so, the conductivity measuring cell is immersed into a series

of aqueous salt solutions with exactly known electric con-

ductiviy. The relevant conductivity values are determined

using the conductivity measuring instrument.

Cell constant Linear factor describing the geometrical dimensions of a

measuring cell and its electrodes.

l With the value of the cell constant you can roughly descri-

be the application range of a conductivity measuring cell.

l The cell constant is determined through calibration in one

or several calibration solutions.

Conductivity The conductivity value is a sum parameter for the ion con-

centration of a test sample.

Control standard

solution

Solution with a known conductivity to determine or check the

conductivity.

Diaphragm Contact point between the reference electrolytic solution

and the sample.


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Multi 720 Lists

161

Drift control See AUTOREAD.

MultiCal Group term for the various WTW calibration procedures

used for automatic calibration in buffer solutions.

OxiCal Automatic calibration

Oxygen saturation Relation of the pO2 in the test sample to the pO2 of air at the

current air pressure. Example: 100% means that the test

sample and the ambient air have the same pO2air and testsample are balanced. According to DIN EN 25814, the oxy-

gen saturation was also referred to as air saturation up to

now.

Oxygen partial pres-

sure

pO2 in mbar, i.e. the gas pressure that would prevail if only

O2 was available.

Redox voltage Potentiometric quantity.

Reference

temperature

In order to compare values measured at different tempera-

tures, the values have to be converted to a fixed tempera-

ture. This temperature is 25 C, or, as an exception, 20 C.

Relative slope Dimensionless factor, referring to the average slope value of

newly regenerated probes of the same type.

Resistance All substances (solids, liquids, or gases) with mobile charge

carriers like for example electrons or ions have a finite ohmic

resistance, which means they have an electric conductance

that can be measured or an electric conducitivtiy.

Resolution Number of decimal places that appear for a measured val-

ue.


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Multi 720 Lists

163

Index

Aasymmetry . . . . . . . . . . . . . . . . . . 102authorized use . . . . . . . . . . . . . . . . 92

AutoCal DIN . . . . . . . . . . . . . 102 , 106

AutoCal TEC . . . . . . . . . . . . . 102 , 104

AutoRead . . . . . . . . . . . 100, 114, 126

criteria . . . . . . . . . . . . . . . . . . . 115

Bbasic settings . . . . . . . . . . . . . . . . 140

battery compartment . . . . . . . . . . . 143

Ccalibrating . . . . . . . . . . . . . . . 102 , 116

calibration . . . . . . . . . . . . . . . . . . . 127

evaluation. . . . . . . . . 102, 117, 129

procedures . . . . . . . . . . . . . . . . 102

start . . . . . . . . . . . . . . . . . . . . . 118

cell constant . . . . . . . . . . . . . 122 , 127

ConCal . . . . . . . . . . . . . . . . . 102 , 108Conductivity . . . . . . . . . . . . . . . . . 123

configuration . . . . . . . . . . . . . . . . . 137

Ddelivery condition . . . . . . . . . . . . . 140

display. . . . . . . . . . . . . . . . . . . . . . . 89

drift control . . . . . . . . . . 100, 114, 126

E

energy saving feature . . . . . . . . . . . 97error messages . . . . . . . 145, 147, 149

Iinitialize . . . . . . . . . . . . . . . . . . . . . 140

Kkeys. . . . . . . . . . . . . . . . . . . . . . . . . 88

LLoBat . . . . . . . . . . . . . . . . . . . . . . 149

Mmeasuring mode on switching on. . 97

measuring ranges. . . . . . . . . . . . . 154

Ooperating structure . . . . . . . . . . . . . 90

operational safety . . . . . . . . . . . . . . 92

oxygen concentration . . . . . . . . . . 112oxygen partial pressure . . . . . . . . 114

oxygen saturation . . . . . . . . . . . . . 113

Pplace of the instrument . . . . . . . . . . 97

plug-in power supply . . . . . . . . . . . 95

RRedox electrode . . . . . . . . . . . . . . 101

Redox voltage . . . . . . . . . . . . . . . 101

reference temperature . . . . . . . . . 139

reference temperature, set . . . . . . 138

replacing the batteries . . . . . . . . . 143

reset . . . . . . . . . . . . . . . . . . . . . . . 140

resistance . . . . . . . . . . . . . . . . . . . 139

resolution . . . . . . . . . . . . . . . . . . . 154

S

safety . . . . . . . . . . . . . . . . . . . . . . . 91safety precautions . . . . . . . . . . . . . 91

salinity correction . . . . . . . . . . . . . 112

enter salinity . . . . . . . . . . . . . . 120

salinity measurement . . . . . . . . . . 124

scope of delivery . . . . . . . . . . . . . . 96

settings, reset . . . . . . . . . . . . . . . . 141

single-point calibration . . . . . . . . . 102

ConCal . . . . . . . . . . . . . . . . . . 110


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Lists Multi 720

slope . . . . . . . . . . . . . . . . . . . 102, 116

sockets . . . . . . . . . . . . . . . . . . . . . .89

Specific resistance . . . . . . . . . . . .123

stirrer, connect. . . . . . . . . . . . . . . . .89

TTDS . . . . . . . . . . . . . . . . . . . . . . . . 125

temperatur probe, set . . . . . . . . . .138

temperature compensation . . . . . .133

temperature probe. . . . . . 98, 111, 123

total dissolved solids measurement . .125

two-point calibration . . . . . . . . . . .102

AutoCal DIN . . . . . . . . . . . . . . .107

AutoCal TEC . . . . . . . . . . . . . .105

ConCal . . . . . . . . . . . . . . . . . . .108

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