instruction manual campbell scientific, inc.s.campbellsci.com/documents/us/manuals/am416.pdf · the...

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AM416 Relay MultiplexerRevision: 2/96

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Warranty and AssistanceThe AM416 RELAY MULTIPLEXER is warranted by CAMPBELLSCIENTIFIC, INC. to be free from defects in materials and workmanship undernormal use and service for twelve (12) months from date of shipment unlessspecified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC,INC.'s obligation under this warranty is limited to repairing or replacing (atCAMPBELL SCIENTIFIC, INC.'s option) defective products. The customershall assume all costs of removing, reinstalling, and shipping defective productsto CAMPBELL SCIENTIFIC, INC. CAMPBELL SCIENTIFIC, INC. willreturn such products by surface carrier prepaid. This warranty shall not applyto any CAMPBELL SCIENTIFIC, INC. products which have been subjected tomodification, misuse, neglect, accidents of nature, or shipping damage. Thiswarranty is in lieu of all other warranties, expressed or implied, includingwarranties of merchantability or fitness for a particular purpose. CAMPBELLSCIENTIFIC, INC. is not liable for special, indirect, incidental, orconsequential damages.

Products may not be returned without prior authorization. The followingcontact information is for US and International customers residing in countriesserved by Campbell Scientific, Inc. directly. Affiliate companies handle repairsfor customers within their territories. Please visit www.campbellsci.com todetermine which Campbell Scientific company serves your country. To obtaina Returned Materials Authorization (RMA), contact CAMPBELLSCIENTIFIC, INC., phone (435) 753-2342. After an applications engineerdetermines the nature of the problem, an RMA number will be issued. Pleasewrite this number clearly on the outside of the shipping container.CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC, INC.RMA#_____815 West 1800 NorthLogan, Utah 84321-1784

CAMPBELL SCIENTIFIC, INC. does not accept collect calls.

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AM416 RELAY MULTIPLEXER MANUALTABLE OF CONTENTS

PDF viewers note: These page numbers refer to the printed version of this document. Usethe Adobe Acrobat® bookmarks tab for links to specific sections.

PAGE1. FUNCTION1.1 Typical Applications....................................................................................................................11.2 Compatibility...............................................................................................................................1

2. PHYSICAL DESCRIPTION .....................................................................................................1

3. AM416 SPECIFICATIONS ......................................................................................................3

4. OPERATION ................................................................................................................................3

4.1 The Control Terminals ...............................................................................................................34.2 The Measurement Terminals .....................................................................................................6

5. DATALOGGER PROGRAMMING5.1 Single Loop Instruction Sequence .............................................................................................65.2 Multiple Loop Instruction Sequence ...........................................................................................95.3 General Programming Considerations.....................................................................................10

6. SENSOR HOOK-UP AND MEASUREMENT EXAMPLES6.1 Single-Ended Analog Measurement without Sensor Excitation ...............................................106.2 Differential Analog Measurement without Sensor Excitation ...................................................116.3 Half Bridge Measurements.......................................................................................................116.4 Full Bridge Measurements .......................................................................................................136.5 Full Bridges with Excitation Compensation ..............................................................................136.6 Thermocouple Measurement ...................................................................................................146.7 Mixed Sensor Types ................................................................................................................16

7. GENERAL MEASUREMENT CONSIDERATIONS .......................................................18

8. INSTALLATION8.1 Environmental Constraints ................................................................................................................18

APPENDIX A. AM416 STUFFING CHART AND SCHEMATICS .................................... A-1

APPENDIX B. DIFFERENCES BETWEEN THE AM416 AND AM32............................ B-2

LIST OF FIGURES

1. Plan View of the AM416 Relay Multiplexer ................................................................................22. Hook-up Diagrams for Datalogger - AM416 Connections..........................................................43. Power and Ground Connections for External Power Supply......................................................54. Actuation Time of Relays vs. Temperature (o) and Battery Voltage ..........................................65. Single Loop Instruction Sequence .............................................................................................66. Example Program Loops for CR10(X), 21X, and CR7 Dataloggers ..........................................8

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7. Wiring Diagram for Strain Gages and Potentiometers...............................................................98. Single-ended Measurement without Excitation ........................................................................119. Differential Measurement without Excitation ............................................................................1110. Half Bridge (Modified 107 Temperature Probe) Hook-up and Measurement ..........................1211. Potentiometer Hook-up and Measurement ..............................................................................1212. Four Wire Half Bridge Hook-up and Measurement..................................................................1313. Differential Measurement with Sensor Excitation.....................................................................1314. Full Bridge Measurement with Excitation Compensation.........................................................1415. Differential Thermocouple Measurement with Reference Junction at the Datalogger.............1516. Differential Thermocouple Measurement with Reference Junction at the AM416...................1517. Thermocouple and Soil Block Measurement ...........................................................................16

CAUTIONARY NOTES

The AM416 is not designed to multiplex power. Its intended function is to switch low level analogsignals. Switched current in excess of 30 mA will degrade contacts and render them unsuitable forfuture low level analog measurements. Customers who need to switch power are directed to CSI'sA6REL-12 or A21REL-12 relays.

Adjacent AM416 channels may be shorted together for up to 5 ms during the clocking procedure. Usersshould consider this when assigning AM416 input channels. Sensors that are capable of sourcingcurrent should not be assigned input terminals adjacent to sensors that can sink current.

This is a blank page.

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AM416 RELAY MULTIPLEXER

1. FUNCTION

The primary function of the AM416 Multiplexeris to increase the number of sensors that maybe scanned by Campbell's CR10(X), 21X andCR7 dataloggers. The AM416 is positionedbetween the sensors and the datalogger;mechanical relays are used to switch thedesired sensor signal(s) through the system.Most commonly, users will multiplex signalsfrom analog sensors into single-ended ordifferential datalogger channels. Four lines areswitched simultaneously; a maximum of sixteensets of (four) lines may be scanned, hence thename A(nalog) M(ultiplexer) 4(lines x) 16(sets).Therefore, a total of 64 lines may bemultiplexed.

The maximum number of sensors that can bemultiplexed through one AM416 dependsprimarily upon the type(s) of sensors to bescanned. Some examples (assuming identicalsensors) follow:

1. Up to 32 single-ended or differentialsensors that do not require excitation (e.g.pyranometers, thermocouples; Sections6.1, 6.2, and 6.6).

2. Up to 48 single-ended sensors that requireexcitation (e.g. some half bridges; Section6.3.1).

3. Up to 16 single-ended or differentialsensors that require excitation (e.g. fullbridges, four-wire half bridge with measuredexcitation; Section 6.3.3 and 6.4).

4. In conjunction with an AM32 multiplexer, upto 16 six-wire full bridges (Section 6.5).

1.1. TYPICAL APPLICATIONS

The AM416 is intended for use in applicationswhere the number of required sensors exceedsthe number of datalogger input channels. Mostcommonly, the AM416 is used to multiplexanalog sensor signals, although it also may beused to multiplex switched excitations,continuous analog outputs, or even certainpulse counting measurements (i.e. those thatrequire only intermittent sampling). It is alsopossible to multiplex sensors of different, butcompatible, types (e.g. thermocouples and soilmoisture blocks, see Section 6.6).

NOTE: For a discussion of single-endedversus differential analog measurements,please consult the Measurement Section ofyour datalogger manual.

As purchased, the AM416 is intended for use inindoor, non-condensing environments. Anenclosure is required for field use. In non-thermocouple applications where a singlemultiplexer is deployed, the AM-ENC enclosureis recommended. In thermocouple applications,CSI recommends use of the AM-ENCTenclosure. If several multiplexers are deployedat the same site in a non-thermocoupleapplication, the 024 or 030 enclosures providecost-effective housing options.

1.2 COMPATIBILITY

The AM416 is compatible with Campbell'sCR10(X), 21X or CR7 dataloggers.

The AM416 is compatible with a wide variety ofcommercially available sensors. As long ascurrent limitations are not exceeded, and nomore than four lines are switched at a time,system compatibility for a specific sensor isdetermined by sensor-datalogger compatibility.

In CR10(X) applications, the AM416 may beused to multiplex up to 16 Geokon vibrating wiresensors through one AVW-1 vibrating wireinterface.

2. PHYSICAL DESCRIPTION

The AM416 is housed in a 21 cm x 16.5 cm x3.5 cm (8.2" x 6.5" x 1.5") anodized aluminumcase (Figure 1). The aluminum case isintended to reduce temperature gradientsacross the AM416's terminal strips. This isextremely important when thermocouples arebeing multiplexed (Section 6.6). The case maybe opened by removing the four #1 phillips-head screws located at the corners of the case.Disassembly of the case may be required tomount the AM416 to a plate or an enclosure(Section 8).

A strain-relief flange is located along the loweredge of the top panel of the case. Severalplastic wire ties are included with the AM416 toattach wires to this flange.


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Wires from sensors and datalogger areconnected to the gray terminal strips. The setof four terminals located near the strain-reliefflange are the connections for dataloggercontrol of the AM416 (Section 4.1). Theterminal strips that run the length of the AM416are for measurement connections (Section 4.2).

The sensor inputs are not spark gapped. Allterminals accept stripped and tinned lead wiresup to 1.5 mm in diameter. The datalogger isconnected to the AM416 through a minimum ofseven, but generally nine, individually insulatedlead wires.

AM416RELAY MULTIPLEXER

SHIELD

L2H2L1

H1

12

11

L2H2L1

H1

L2H2L1

H1

SHIELDL2

H2

10

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H2

L1H1

9

SHIELD

SHIELD

L2H2L1

H1

16

15

L2H2L1

H1

L2H2L1

H1

14

L2

H2

L1H1

13

SHIELD

SHIELD

L2H2L1

H1

8

7

L2H2L1

H1

L2H2L1

H1

SHIELDL1

H1

6

CO

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L2

H2

L1H1

5

SHIELD

SHIELD

L2H2L1

H1

4

3

L2H2L1

H1

L2H2L1

H1

2

L2

H2

L1H1

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FIGURE 1. Plan View of the AM416 Relay Multiplexer


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3. AM416 SPECIFICATIONS

POWER*: unregulated 12 VDC (9.6 V to 16 V)- See Figure 4 for implications of low power torelay actuation

CURRENT DRAIN:Quiescent: < 100 uAActive: 17 mA (typical)

RESET*: a continuous signal of 3.5VDC <voltage < 16 VDC holds AM416 in an activestate (i.e. a clock pulse can trigger a scanadvance). A signal voltage of < 0.9VDCdeactivates the AM416 (clock pulse will nottrigger a scan advance; AM416 is also reset).

CLOCK*: on the transition from <1.5 V to >3.5V, scan advance is actuated on the leadingedge of the clock signal; clock signal must be aminimum of 5 ms in width.

OPERATIONAL TEMPERATURE: -40oC to+65oC

OPERATIONAL HUMIDITY: 0 - 95%, non-condensing

DIMENSIONS (without field enclosure):length - 21 cm (8.2")width - 16.5 cm (6.5")depth - 3.5 cm (1.5")

(with field enclosure i.e. box size):length - 25.4 cm (10.0")width - 20.3 cm (8.0")depth - 10.2 cm (4.0")

WEIGHT: 1.5 lbs (approx.)(in enclosure): 10.0 lbs (approx.)

EXPANDABILITY**(nominal):3 AM416'S/CR10(X)4 AM416'S/21X8 AM416's/CR7 725 Card

MAXIMUM CABLE LENGTH: sensor & scanrate dependent (in general, longer lead lengthsnecessitate longer measurement delays. Referto datalogger manual for additional details).

MAXIMUM SWITCHING CURRENT***: 500 mA

* Reset, Clock, and +12V inputs are limited to+16V by 1.5KE20A transzorbs.

** Assumes sequential activation of multiplexersand that each datalogger channel is uniquelydedicated. If your application requiresadditional multiplexing capability, please consultCSI for application assistance.

*** Switching currents greater than 30 mA(occasional 50 mA is acceptable) will degradethe contact surfaces of the mechanical relays(i.e. increase their resistance). This process willadversely affect the suitability of these relays tomultiplex low voltage signals. Although a relayused in this manner will not be of use in futurelow voltage measurements, it may continue to beused for switching current in excess of 30 mA.

CONTACT SPECIFICATIONS

Initial contact resistance: 50 mohm max.Initial contact bounce: 1 ms max.Contact material: Gold clad silver alloyElectrostatic capacitance: 3pFMinimum expected life:

Mechanical (at 50cps): 108 openElectrical (at 20cps): 2 x 105

CHARACTERISTICS (at 25oC, 50% RelativeHumidity)

Operate time 8 to 15 ms approx. (See Figure 4)Release time 5 ms approx.

4. OPERATION

Subsection 4.1 discusses the use of theterminals that control operation of themultiplexer. These terminals are located alongthe lower left side of the multiplexer as shown inFigure 1. Subsection 4.2 discusses the use ofterminals used in sensor measurement.

4.1. THE CONTROL TERMINALS

The CR10(X), 21X and CR7 dataloggers shouldbe connected to the AM416 as shown in Figure2. This figure depicts control connections;measurement connections are discussed inSection 6. The power, ground, reset, and clockconnections remain essentially the sameregardless of datalogger used.

In a CR10(X) application, the datalogger 12VDCsupply and ground terminals are connected tothe AM416 12V and ground terminals. Twocontrol ports are used for clock and reset.


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FIGURE 2. Hook-up Diagrams for Datalogger - AM416 Connections

CR10(X) Hook-up 21X Hook-up

CR7 Hook-up

The 21X or CR7 (with a 725 Card) can be usedto connect 12VDC supply and ground to theAM416. One control port is used for reset, andone switched excitation channel is used forclock. If switched excitations are unavailable, acontrol port may be used to provide clockpulses to the multiplexer.

4.1.1 RESET

Reset (RES) controls activation of themultiplexer. A voltage (3.5VDC <voltage<16VDC) applied to this terminal activates themultiplexer. When this line is dropped to<0.9VDC, the multiplexer enters a quiescent,low current drain state. Reset is alwaysconnected to a datalogger control port.Instruction 86 (option code 41 - 48 [activate]and 51 - 58 [deactivate]) is generally used.With a 21X or CR7 with older PROMS,Instruction 20 is commonly used to activate anddeactivate the multiplexer (set port high to

activate the multiplexer or low to enterquiescent mode).

4.1.2 CLOCK

The multiplexer clock line (CLK) controls theswitching between sequential sets of relays.When reset is set high and the multiplexer isactivated, the multiplexer's common lines (COMH1, COM L1 COM H2, COM L2) are notconnected to any of the sensor input terminals.When the first clock pulse is received, thecommon lines are switched into connection withmultiplexer channel 1 (H1,L1,H2,L2). When asecond clock pulse is received, the commonlines are connected to multiplexer channel 2(H1,L1,H2,L2). Adjacent Multiplexer inputchannels are momentarily shorted to each otherduring the switch (e.g. channel 1 H1 to channel2 H1, channel 1 L1 to channel 2 L1, etc. SeeCautionary Notes). The multiplexer is clockedon the leading edge of the voltage pulse. The


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voltage level must fall below 1.5VDC thenexceed 3.5VDC to clock. Pulse width must beat least 5 ms. An additional delay is requiredbefore the measurement to ensure adequatetime for the relay to close.

In the 21X and CR7 dataloggers, a switchedexcitation is generally used to clock themultiplexer (Instruction 22 - 5,000 mVexcitation). If no switched excitation channelsare available it is possible to clock using controlports. See Section 5.1 for additional details.

In the CR10(X) datalogger, a control port isgenerally used to clock the multiplexer.Instruction 86 with the pulse port option(command code 71 through 78 - generates apulse 10 ms in width) may be used to clock themultiplexer.

4.1.3 GROUND

The multiplexer ground terminal is connected todatalogger power ground. If a separate powersupply is used, AM416 ground is alsoconnected to the power supply ground (Figure3). The datalogger should always be tied toearth ground by one of the methods describedin the Installation/Maintenance Section of yourdatalogger manual.

4.1.4 POWER SUPPLY

The AM416 requires a continuous 9.6 to 16VDC power supply for operation. Themultiplexer's current drain is less than 100microamps while quiescent and is typically 17milliamps at 12 VDC when active. Powersupply connections are made at the terminalslabeled 12V and GND.

In many applications, it may be convenient topower the AM416 from the datalogger's battery.For more power-intensive operations, anexternal, rechargeable, 12VDC, 60-AmpHrsource may be advisable. Because of theirability to be recharged, lead-acid supplies arerecommended where solar- or AC- chargingsources are available. The datalogger alkalinesupply (7.5 AmpHr) can be used to power theAM416 in applications where the system currentdrain is low, or where frequently replacing thebatteries is not a problem. It is advisable tocalculate the total power requirements of thesystem and the expected longevity of the powersupply based on the system current drains (e.g.the datalogger, multiplexer, other peripherals

and sensors) and the expected ambienttemperatures.

The power required to operate an AM416depends on the percentage of time it is active.For example, if a CR10(X) makes differentialmeasurements on 32 thermocouples everyminute, the average current drain due to theAM416 is about 0.3 mA. Under the sameconditions, a 2 second scan rate increases theaverage system current drain to about 8.5 mA.At a minimum, the power supply must be ableto sustain the system between site visits overthe worst environmental extremes.

If a 21X power supply is used to power theAM416, all low level analog measurements(thermocouples, pyranometers, thermo-piles,etc.) must be made differentially. Thisprocedure is required because slight groundpotentials are created along the 21X analogterminal strip when the 12V supply is used topower peripherals. This limitation reduces thenumber of available analog input channels andmay mandate the use of an external supply forthe AM416 (Figure 3).

FIGURE 3. Power and Ground Connectionsfor External Power Supply.

Low power and high ambient temperatures mayaffect the actuation time of the multiplexerrelays (Figure 4). If the relay is not closed whena measurement is started, the result will be aninaccurate or overranged value.


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FIGURE 4. Actuation Time of Relays vs.Temperature (oC) and Battery Voltage.

4.2 THE MEASUREMENT TERMINALS

The terminals that run the length of the AM416are dedicated to the connection of sensors tothe datalogger (Figure 1). The 16 groups of 4-terminal inputs allow attachment of stripped andtinned sensor leads. The terminals markedCOM allow attachment of the common signalleads that carry the sensor's signal betweenmultiplexer and datalogger. The shield linesallow sensor shields to be routed through themultiplexer and back to datalogger ground.

4.2.1 THE COM TERMINALS

The multiplexer terminals dedicated tomultiplexer-datalogger signal transfer arelocated within the silk screened bracketslabeled COM (common; see Figure 1). Thefour individual COM lines are labeled: H1(common high #1), L1 (common low #1), H2(common high #2), and L2 (common low #2).The circuitry of each COM line is isolated fromthe other three.

A shield terminal is also located within eachCOM bracket. All shield terminals are inelectrical continuity at all times (i.e. they are notswitched). Their function is to provide a path toground for sensor cable shields. The shieldterminals within the COM bracket should be tiedto datalogger earth ground either directly orthrough a busbar.

4.2.2 THE SENSOR INPUT TERMINALS

The input terminals for sensor attachment runthe length of the multiplexer and are subdividedinto 16 labeled groups. Each group consists offour Simultaneously Enabled Terminals (SET).

Within each SET, the four terminals are labeledH1, L1, H2, L2. As the AM416 receives clockpulses from the datalogger, each SET isswitched sequentially into contact with the COMterminals. For example, when the first clockpulse is received from the datalogger, SET 1(bracket annotated with a number 1) isconnected with the COM lines. T terminal H1 isconnected to COM H1, terminal L1 to COM L1,terminal H2 to COM H2, and terminal L2 toCOM L2. When the second clock pulse isreceived, the first SET is switched out(becomes an open circuit) and the second SET(bracket annotated with a number 2) isconnected to the COM terminals.

5. DATALOGGER PROGRAMMING

When a number of similar sensors aremultiplexed and measured, the Instructions toclock the AM416 and to measure the sensorsare entered within a program loop. Thegeneralized structure of a program loop isoutlined below:

5.1 SINGLE LOOP INSTRUCTION SEQUENCE

FIGURE 5. Single Loop Instruction Sequence

(1 and 9) Activate/Deactivate AM416 - Thecontrol port connected to reset (RES) is set highto activate the AM416 prior to the measurementsequence and set low following themeasurement loop(s). Instruction 86 is used toset the port. (With the CR10(X), 21X, and CR7without OS series PROMS, Instruction 20 isused.)

(2 and 7) Loop - A loop is defined by Instruction87 (begin loop), and by an end instruction, 95.Within Instruction 87, the 2nd parameter(iteration count) defines the number of timesthat the instructions within a loop are executedbefore the program exits the loop.


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(3) Clock/Delay - With the CR10(X), the clockline is connected to a control port. Instruction86 with the pulse port command (71- 78), setsthe clock line high for 10 ms. Instruction 22 isused to delay an additional 10 ms.

When controlled by the 21X or CR7, the clockline may be connected to either an excitation ora control port. Connection to an excitation portis preferred because only one instruction (22) isrequired to send the clock pulse. Instruction 22should be programmed to provide a 10ms delaywith a 5000mV excitation. A control port can beused to clock the AM416 if no excitation portsare available. The 21X and CR7 instructionsequence required to clock with a control portis: Instruction 20 (set port high), Instruction 22(delay of 20 ms without excitation) followed byInstruction 20 (set port low).

(4) Step Loop Index - This instruction is usedwhen a measurement instruction within thatloop has more than one repetition. It allowseach measurement value to occupy asequentially assigned input location withoutbeing overwritten by subsequent passesthrough the loop. Without this instruction, eachindexed input location within the loop willadvance by only one location per loop iteration.

For Example: 2 sensors per SET, 6 sensorstotal; two reps in measurement instruction; twomeasurement values assigned to indexed inputlocations (--); P90 step of 2. Loop count ofthree.

Input locations1 2 3 4 5 6

First pass: 1 2Second pass: 3 4 sensorThird pass: 5 6 numbers

Given the same program without a step loopinstruction, the following situation results:



The measurement values for the 2nd and 4thsensors will be overwritten in their inputlocations. The 1st, 3rd, 5th, and 6thmeasurement values will reside in the first 4input locations.

The Step Loop Instruction 90 is available inCR10(X)s, CR7s, and 21Xs with a third PROM.For 21X dataloggers without a third prom (i.e.without Instruction 90), a separatemeasurement instruction (with one rep) isrequired for each sensor measured within theloop. The input location parameter within bothmeasurement instructions is indexed.

For Example: 2 sensors per SET; one rep ineach of two measurement instructions; twomeasurement values assigned to indexed inputlocations (--), one begins with input location 1,the other with input location 4; no P90. A totalof six sensors to be measured; loop count isthree.



A potential drawback of this technique is thatsequential sensors (i.e. those input to the sameSET) will not have sequential input locations.

(5) Measure - Enter the instruction needed tomeasure the sensor(s) [see Section 6, SensorHook-Up & Measurement Examples]. The inputlocation parameter of a measurementinstruction is indexed if a (--) appears to theright of the input location. Index an inputlocation by pressing "C" after keying thelocation. Indexing causes the input location tobe incremented by 1 with each pass through theloop. This allows the measurement value to bestored in sequential input locations. Instruction90, as explained above, allows the indexedinput location to be incremented in integer stepsgreater than 1.

NOTE: If more than 28 input locations areutilized, then additional input locations mustbe assigned using the datalogger *A mode.Consult your datalogger manual for details.

(6) Optional Processing - Additional processingis sometimes required to convert the reading tothe desired units. It may be more efficient orreduce measurement time if this processing isdone outside the measurement loop. A secondloop can be used for processing, if necessary.


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EXAMPLE PROGRAMS - GENERALIZED PROGRAM LOOPS FOR THE CR10(X), 21X AND CR7.

21X SAMPLE PROGRAM* 1 Table 1

Programs01: 60 Sec.

ExecutionInterval

ACTIVATES MULTIPLEXER01: P20 Set Port

01: 1 Set high02: 1 Port

Number

BEGINS MEASUREMENTLOOP02: P87 Beginning

of Loop01: 0 Delay02: 16 Loop Count

CLOCK PULSE AND DELAY03: P22 Excitation

with Delay01: 1 EX Chan02: 1 Delay w/EX

(units=.01sec)

03: 1 Delay afterEX (units=.01 sec)

04: 5000 mVExcitation

04: USER SPECIFIEDMEASUREMENTINSTRUCTION

ENDS MEASUREMENTLOOP05: P95 End

DEACTIVATES MULTIPLEXER06: P20 Set Port

01: 0 Set low02: 1 Port

Number

CR7 SAMPLE PROGRAM* 1 Table 1

Programs01: 60 Sec.

ExecutionInterval

ACTIVATES MULTIPLEXER01: P20 Set Port

01: 1 Set high02: 1 EX Card03: 1 Port No.



CLOCK PULSE AND DELAY03: P22 Excitation

with Delay01: 1 EX Card02: 2 EX Chan03: 1 Delay w/EX

(units=.01sec)

04: 1 Delay afterEX (units=.01 sec)

05: 5000 mVExcitation



DEACTIVATES MULTIPLEXER06: P20 Set Port

01: 0 Set low02: 1 EX Card03: 1 Port No.

CR10(X) SAMPLE PROGRAM* 1 Table 1

Programs01: 60 Sec.

ExecutionInterval

ACTIVATES MULTIPLEXER01: P86 Do

01: 41 Set highPort 1



CLOCK PULSE03: P86 Do

01: 72 Pulse Port2

DELAYP22 Excitation

with Delay01: 1 EX Chan02: 0 Delay w/EX03: 1 Delay after EX04: 0 mV

Excitation



DEACTIVATES MULTIPLEXER06: P86 Do

01: 51 Set lowPort 1

FIGURE 6. Example Program Loops for CR10(X), 21X and CR7 Dataloggers.


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FIGURE 7. Wiring Diagram for Strain Gages and Potentiometers

(8) Additional Loops - Additional loops may beused if sensors that require differentmeasurement instructions are connected to thesame multiplexer. In this instance, like sensorsare assigned to sequential input SETS. Eachgroup of sensors is measured in a separateloop (steps 2 through 7, Figure 4). Each loopcontains clock and measurement instructions,and all loops must reside between theinstructions that activate and deactivate theAM416 (Steps 1 and 9).

The instruction sequence for control of anAM416 is given on the following page. TheProgram format is a product of EDLOG, adatalogger program editor contained in CSI'sPC208 Datalogger Support Software.

5.2 MULTIPLE LOOP INSTRUCTION SEQUENCE

As shown above, the program for operation ofthe AM416 is essentially the same for all CSIdataloggers. To measure sensors of differenttypes, different measurement instructions maybe used within successive program loops. Inthe following example, each loop is terminatedwith Instruction 95, and the multiplexer is notreset between loops. The following exampledemonstrates measurement of two dissimilarsensor types (i.e. strain gages andpotentiometers).

The program and accompanying wiring diagramare intended as examples only; users will find itnecessary to modify both for specificapplications.

* 1 Table 1 Programs01: 60 Sec. Execution Interval

ENABLES MULTIPLEXER01: P20 Set Port

01: 1 Set high02: 1 Port Number

BEGINS STRAIN GAGE MEASUREMENT LOOP02: P87 Beginning of Loop

01: 0 Delay02: 10 Loop Count

CLOCK PULSE03: P22 Excitation with Delay

01: 1 EX Chan02: 1 Delay w/EX (units=.01sec)03: 1 Delay after EX (units=.01sec)04: 5000 mV Excitation

FULL BRIDGE MEASUREMENT INSTRUCTION04: P6 Full Bridge

01: 1 Rep02: 3 50 mV slow Range03: 1 IN Chan04: 2 Excite all reps w/EXchan 205: 5000 mV Excitation06: 1-- Loc [:STRAIN #1]07: 1 Mult08: 0 Offset

END OF STRAIN GAGE MEASUREMENT LOOP05: P95 End


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BEGINNING OF POTENTIOMETERMEASUREMENT LOOP06: P87 Beginning of Loop


07: P90 Step Loop Index (Extended)01: 2 Step

CLOCK PULSE08: P22 Excitation with Delay

01: 1 EX Chan02: 1 Delay w/EX (units=.01sec)03: 1 Delay after EX (units=.01sec)04: 5000 mV Excitation

POTENTIOMETER MEASUREMENTINSTRUCTION09: P4 Excite,Delay,Volt(SE)

01: 2 Reps02: 5 5000 mV slow Range03: 1 IN Chan04: 2 Excite all reps w/EXchan 205: 1 Delay (units .01sec)06: 5000 mV Excitation07: 11-- Loc [:POT #1 ]08: 1 Mult09: 0 Offset

END OF POTENTIOMETER MEASUREMENTLOOP10: P95 End

DISABLES MULTIPLEXER11: P20 Set Port

01: 0 Set low02: 1 Port Number

12: P End Table 1

INPUT LOCATION LABELS: 1:STRAIN #1 13:POT #3 2:STRAIN #2 14:POT #4 3:STRAIN #3 15:POT #5 4:STRAIN #4 16:POT #6 5:STRAIN #5 17:POT #7 6:STRAIN #6 18:POT #8 7:STRAIN #7 19:POT #9 8:STRAIN #8 20:POT #10 9:STRAIN #9 21:POT #1110:STRAIN#10 22:POT #1211:POT #1 23:_________12:POT #2 24:_________

5.3 GENERAL PROGRAMMINGCONSIDERATIONS

The excitation voltage, integration and delaytimes associated with reading the signal, andthe speed with which the channels are switchedmay be varied with the datalogger program. Ingeneral, longer delay times are necessary whenthe sensor and datalogger are separated bylong lead lengths. Consult your dataloggermanual for additional information on thesetopics.

6. SENSOR HOOK-UP ANDMEASUREMENT EXAMPLES

This section covers sensor-AM416 connectionsas well as AM416-datalogger measurementconnections. The following are examples only,and should not be construed as the only way tomake a particular measurement. See theMeasurement Section of your dataloggermanual for more information on the basic bridgemeasurements. Most of the following examplesdo not depict datalogger-AM416 controlconnections (Section 4), but their presence isimplied and required. CSI recommends thatonly sensor shield (drain) wires be connected toAM416 shield terminals.

6.1 SINGLE-ENDED ANALOG MEASUREMENTWITHOUT SENSOR EXCITATION

Sensor to Multiplexer wiring - up to two single-ended sensors that don't require excitation maybe connected to one AM416 input SET.

Multiplexer to Datalogger wiring - Signal linesfrom COM terminals are input into twoconsecutive single-ended analog inputchannels. Signal ground lines are tied to analogground (AG) in the CR10(X), datalogger groundin the 21X and CR7. The COM shield line istied to datalogger earth ground. Up to 32single-ended sensors may be used by twosingle-ended datalogger channels in thismanner.

NOTE: Low level single-endedmeasurements are not recommended in a21X application in which the 21X's internal12VDC supply is being used to power themultiplexer or other peripherals (Section4.1.4).


11

FIGURE 8. Single-ended Measurement Without Excitation

FIGURE 9. Differential Measurement Without Excitation

6.2 DIFFERENTIAL ANALOG MEASUREMENTWITHOUT SENSOR EXCITATION

Sensor to Multiplexer wiring - Up to twodifferential sensors that don't require excitationmay be connected to one input SET. Sensorshields are routed through shield terminals.

Multiplexer to Datalogger wiring - A pair ofCOM terminals (e.g. COM H1 and COM L1) isconnected to a differential analog input at thedatalogger. Up to 32 differential sensors maybe measured by two differential dataloggerchannels in this way.

6.3 HALF BRIDGE MEASUREMENTS

Measurements of this type may be subdividedinto three categories based on completionresistance and the presence or absence ofmeasured excitation. If the sensor's completionresistor(s) are installed at the datalogger panel(e.g. a CSI 107 probe modified for multiplexeruse), then three probes per SET may be excitedand measured (Figure 10). However, if thecircuit is completed within the sensor (e.g.

potentiometers), then excitation, wiper signal,and ground must be multiplexed. Becauseexcitation and ground may be multiplexed incommon, up to two sensors per SET may bemeasured (Figure 11). If measured excitation isrequired (i.e. four wire half-bridge), then onlyone sensor per SET may be measured (Figure12).

6.3.1 HALF BRIDGE MEASUREMENT WITHCOMPLETION RESISTOR(S) ATDATALOGGER

Sensor to Multiplexer wiring - up to three halfbridges may be connected to one input SET,provided that the sensor's completion resistorsare located at the datalogger (Figure 10).

Multiplexer to Datalogger wiring - Signal linesfrom the multiplexer COM terminals are inputinto three consecutive single-ended analoginput channels. A precision completion resistorties the analog input channel to analog groundin the CR10(X) or to datalogger ground in the21X or CR7.


12

FIGURE 10. Half Bridge (Modified 107 Temperature Probe) Hook-up and Measurement.

FIGURE 11. Potentiometer Hook-up and Measurement

6.3.2 POTENTIOMETER MEASUREMENT

Sensor to Multiplexer wiring - up to twopotentiometers may be connected to one inputSET. Excitation and ground leads may becommon; signal leads must be routedseparately (Figure 11).

Multiplexer to Datalogger wiring - Signal linesfrom two COM terminals are connected to twoconsecutive single-ended analog inputchannels. One COM terminal is connected to adatalogger switched excitation channel, and theremaining COM line connects to dataloggerground. Up to 32 potentiometers may bemeasured by two single-ended dataloggerchannels.

6.3.3 FOUR WIRE HALF BRIDGE WITHMEASURED EXCITATION

Sensor to Multiplexer Wiring - one sensor perinput SET.

Multiplexer to Datalogger Wiring - One COMline is tied to a datalogger excitation channel,and two COM lines to a differential analog input.The remaining COM line is connected to thehigh side of a differential channel along with afixed resistor. The other side of the resistorconnects to the low side of the channel, thenground (Figure 12). Up to 16 four wire half-bridges may be measured by two differentialdatalogger channels in this manner.


13

FIGURE 12. Four Wire Half Bridge Hook-up and Measurement

FIGURE 13. Differential Measurement with Sensor Excitation

6.4 FULL BRIDGE MEASUREMENTS

Sensor to Multiplexer wiring - Excitation,ground, and the two signal leads may beconnected to one input SET (Figure 13).

Multiplexer to Datalogger wiring - COMterminals are connected to a dataloggerexcitation channel, a differential analog inputchannel, and analog ground. Up to sixteen fullbridges may be multiplexed through the AM416.

6.5 FULL BRIDGES WITH EXCITATIONCOMPENSATION

Sensor to Multiplexer wiring - In a six wiremeasurement, two wires must bypass theAM416. One solution is to multiplex the foursignal wires through the AM416, but bypass the

AM416 with excitation and ground. This meansthat the sensors will be excited in common,which causes a higher current drain, possiblyexceeding the current available from thedatalogger's excitation channels. Alternatively,the excitation and ground leads may bemultiplexed through either an AM32 multiplexeror an additional AM416. This allows thesensors to be excited one at a time (Figure 14).

Multiplexer to Datalogger wiring - Four leadsfrom the COM terminals to two sequentialdifferential analog channels in the datalogger.Excitation and ground are multiplexed by aAM32 or AM416. Both multiplexers can bereset and clocked by the same control portsand/or excitation channels, which simplifiesprogramming.


14

FIGURE 14. Full Bridge Measurement with Excitation Compensation

6.6 THERMOCOUPLE MEASUREMENT

The datalogger manuals contain thoroughdiscussions of thermocouple measurement anderror analysis. These topics will not be coveredhere.

6.6.1 MEASUREMENT CONSIDERATIONS

Reference Junction - As shown in Figure 15 and16, two reference junction configurations arepossible: reference at the datalogger orreference at the AM416.

Datalogger Reference - The 21X and the CR7723-T Analog Input card with RTD have built-intemperature references. The 10TCRTThermocouple Reference (not standard withCR10(X) purchase), is installed on the wiringpanel between the two analog input terminalstrips.

When the reference junction is located at thedatalogger, the signal wires between the data-logger and the AM416 must be of the same wiretype as the thermocouple (Figure 15). The"polarity" of the thermocouple wire must bemaintained on either side of the multiplexer(e.g. if constantan wire is input to a L1 terminal,then a constantan wire should run between the

multiplexer's COM L1 terminal and thedatalogger measurement terminal). Figures 15& 16 depict type T thermocouple applications,but other thermocouple types (e.g. E, J, and K)may also be measured and linearized by thedataloggers.

If thermocouples are measured with respect tothe datalogger reference, then concurrentmeasurement of any other sensor type throughthe AM416 is not recommended. Two problemswill be encountered if this is done. Bothproblems result from the compositionaldifferences of the thermocouple wires.

1. An extraneous thermocouple voltage will beadded to the non-thermocouple signal atthe junction of dissimilar metals (e.g. themultiplexer COM terminals). Themagnitude of this signal will vary with thetemperature difference between thedatalogger and the AM416.

2. Some thermocouple wires have a greaterresistance than copper, which addsresistance to the non-thermocouple sensorcircuit. For example, constantan isapproximately 26 times more resistive thancopper.


15

FIGURE 15. Differential Thermocouple Measurement with Reference Junction at the Datalogger.

FIGURE 16. Differential Thermocouple Measurement with Reference Junction at the AM416.

If a mix of TC's and other sensor types aremultiplexed through the AM416, it is generallybest to locate the reference junction on theAM416, as shown in Figure 16.

AM416 Reference - An external reference,usually a thermistor, may be located at theAM416, as shown in Figure 16. This approachrequires an additional single-ended dataloggerinput to measure the reference. Locate thereference between the COM terminals and,when practical, measure the thermocouples onSETs that are in close proximity to the COMterminals in order to minimize thermalgradients.

Thermal Gradients - Thermal gradients betweenthe AM416's sensor input terminals and COM

terminals can cause errors in thermocouplereadings. For example, with type Tthermocouples, a one degree gradient betweeninput terminals and the COM terminals willresult in a one degree measurement error(approximately). The aluminum cover platehelps to minimize gradients, but for best results,the AM416 should be shielded and insulatedfrom thermal sources.

When an enclosure is used, gradients inducedfrom heat conducted along the thermocouplewire can be minimized by coiling some wireinside the enclosure. This procedure allows theheat to dissipate before it reaches the terminal.If the AM416 is housed in a field enclosure, theenclosure should be shielded from solarradiation.


16

6.6.2 SINGLE-ENDED THERMOCOUPLEMEASUREMENT

In single-ended thermocouple measurement,the following precautions must be taken toensure accurate measurement:

1. Only shielded thermocouple wire should beused; the sensor shields should be tied todatalogger earth ground through themultiplexer shield terminals.

2. The exposed end of the thermocoupleshould be electrically insulated to preventdifferences in ground potential from causingan error in the measured temperature.

Sensor to Multiplexer wiring - up to threethermocouples per SET; the high side of eachthermocouple is input into terminals H1, L1, andH2. The low sides of each thermocouple aremultiplexed in common through terminal L2.

Multiplexer to Datalogger wiring - If thereference junction is at the datalogger, then thewire that connects the COM H1, COM L1, andCOM H2 terminals to the datalogger should bethe same composition as the high side of thethermocouples. Also, the wire that connectsCOM L2 to datalogger ground should be thesame composition as the low side of thethermocouples.

If the reference junction is at the AM416 (CSI107 thermistor, RTD, etc.), then copper wire isused to connect all COM terminals to thedatalogger.

6.6.3 DIFFERENTIAL THERMOCOUPLEMEASUREMENT

Sensor to Multiplexer wiring - up to twothermocouples per input SET.

Multiplexer to Datalogger wiring - The wireshere can be handled in one of two ways. If areference junction (107 thermistor, RTD, etc.) isat the AM416, then two pair of copper wiresmay be run between the COM terminals of themultiplexer and two differential input channels.

If the reference junction is at the datalogger,then two pairs of thermocouple wire should berun between the COM terminals of themultiplexer and two differential input channels.

6.7 MIXED SENSOR TYPES

In applications where sensors types are mixed,multiple hook-up configurations andprogramming sequences are possible. Pleaseconsult CSI for application assistance if youintend to multiplex markedly different sensortypes in your application.

6.7.1 MIXED SENSOR EXAMPLE: SOILMOISTURE BLOCKS ANDTHERMOCOUPLES

In this example, 16 thermocouples and 16 soilmoisture blocks will be multiplexed through theAM416. One thermocouple and one soilmoisture block are input into each SET.

FIGURE 17. Thermocouple and Soil Block Measurement


17

EXAMPLE PROGRAM - THERMOCOUPLEAND SOIL BLOCK MEASUREMENT

(PROGRAM IS FOR CR10(X) - 33LOCATIONS ALLOCATED TO INPUTSTORAGE)

* 1 Table 1 Programs01: 60 Sec. Execution Interval

REFERENCE TEMPERATURE FORTHERMOCOUPLES01: P11 Temp 107 Probe

01: 1 Rep02: 4 IN Chan03: 1 Excite all reps w/EXchan 104: 1 Loc [:REFTEMP ]05: 1 Mult06: 0 Offset

ENABLES MULTIPLEXER02: P86 Do

01: 41 Set high Port 1

BEGINS MEASUREMENT LOOP03: P87 Beginning of Loop


CLOCK PULSE04: P86 Do

01: 72 Pulse Port 2

05: P22 Excitation with Delay01: 1 EX Chan02: 2 Delay w/EX (units=.01 sec)03: 0 Delay after EX (units=.01 sec)04: 1 mV Excitation05: 0

MEASURES 1 THERMOCOUPLE PER LOOP06: P14 Thermocouple Temp(DIFF)

01: 1 Rep02: 1 2.5 mV slow Range03: 1 IN Chan04: 1 Type T (Copper-Constantan)05: 1 Ref Temp Loc REFTEMP06: 2-- Loc [:TC #1 ]07: 1 Mult08: 0 Offset

MEASURES 1 SOIL MOISTURE BLOCK PERLOOP07: P5 AC Half Bridge

01: 1 Rep02: 14 250 mV fast Range03: 3 IN Chan04: 2 Excite all reps w/EXchan 205: 250 mV Excitation06: 18-- Loc [:SOIL M #1]07: 1 Mult08: 0 Offset

ENDS MEASUREMENT LOOP08: P95 End

DISABLES MULTIPLEXER09: P86 Do

01: 51 Set low Port 1

CALCULATES BRIDGE TRANSFORM ONSOIL MOISTURE BLOCKS10: P59 BR Transform Rf[X/(1-X)]

01: 16 Reps02: 18 Loc [:SOIL M #1]03: 1 Multiplier (Rf)

11: P End Table 1

INPUT LOCATION LABELS:

1:REFTEMP 19:SOIL M #22:TC #1 20:SOIL M #33:TC #2 21:SOIL M #44:TC #3 22:SOIL M #55:TC #4 23:SOIL M #66:TC #5 24:SOIL M #77:TC #6 25:SOIL M #88:TC #7 26:SOIL M #99:TC #8 27:SOIL M#1010:TC #9 28:SOIL M#1111:TC #10 29:SOIL M#1212:TC #11 30:SOIL M#1313:TC #12 31:SOIL M#1414:TC #13 32:SOIL M#1515:TC #14 33:SOIL M#1616:TC #15 34:_________17:TC #16 35:_________18:SOIL M #1 36:_________


18

7. GENERAL MEASUREMENTCONSIDERATIONS

1. Long lead lengths - long lead lengthscontribute to the formation of induced andcapacitive voltages within the sensor andAM416 lead wires. To minimize thisphenomenon, CSI recommends use ofTeflon, polyethylene, or polypropyleneinsulation around individual conductors. Donot use PVC insulation as conductorinsulation, although it may be used as acable jacket. It may also be necessary toprogram a delay within the measurementinstruction in order to allow the capacitanceof the lead wires to discharge beforemeasurement. Please consult the theory ofoperation section of your datalogger manualfor more information.

2. Common Earth Ground - A connection toearth ground should be made at thedatalogger. The lead wire that connects thedatalogger power ground to the AM416power ground establishes a commonground. The Installation/MaintenanceSection of your datalogger manual hasmore for information on groundingprocedures.

3. Completion resistors - In some applicationsit may be advisable to place completionresistors at the datalogger terminal strips.In some cases, sensors specific to the useof multiplexers are available from CSI.Examples include soil moisture probes andthermistors. Please consult CSI forordering and pricing information.

4. Contact degradation - Once excitation inexcess of 30 mA has been multiplexed, thatset of contacts may be rendered unsuitablefor later low voltage measurement. Toprevent undue degradation, it is advisableto reserve certain channels for sensorexcitations and other channels for sensorsignals.

8. INSTALLATION

The standard AM416 may be operated in anindoor, non-condensing environment. Ifcondensing humidity is a problem or if themultiplexer might be exposed to liquids, awater-resistant enclosure is required.

Several enclosures may be purchased throughCSI which offer a degree of protection againstdust, spraying water, oil, falling dirt, or drippingnoncorrosive liquids (Models AM-ENC, AM-ENCT, ENC-24, ENC-30). All the enclosurescontain mounting plates for the multiplexer andconduit bushings for cable entry. Thesestandard enclosures are rain-tight, but notwater-proof.

The AM416 is attached to the mounting plateinside the enclosure with two screws. Toexpose these screws, the top plate of themultiplexer (four #1 phillips screws at thecorners) and the printed circuit board (twostraight-slot screws near the center of theboard) must be removed. Care must be takenwhen removing the upper plate of themultiplexer. It is generally easiest to lift theedge opposite the strain relief flange up first,then slide the upper plate out. Make sure toclear the terminal strips.

The enclosure lids are gasketed. The screwson the outside of the enclosure should betightened to form a restrictive seal. In highhumidity environments, user supplied foam orputty (or a similar substance) helps to reducethe passage of moisture into the enclosure viathe cable conduits. [CAUTION: Air movementshould not be restricted into any enclosurecontaining batteries that may produce explosiveor noxious gases (e.g. lead-acid cells)]. U-boltsare provided to attach the enclosure to a 1.25"diameter pipe. The enclosure may also be lag-bolted to a wall or similar flat surface.

8.1 ENVIRONMENTAL CONSTRAINTS

The AM416 has an operable temperature rangeof -40oC. to +65oC. The multiplexer issusceptible to corrosion at high relativehumidity. Desiccant packs are available fromCSI and they should be used inside theenclosure to remove water vapor.

A-1

APPENDIX A. AM416 STUFFING CHART AND SCHEMATICS


A-2


A-3


A-4


B-1

APPENDIX B. DIFFERENCES BETWEEN THE AM416 AND THE AM32

The AM416 differs from Campbell Scientific'sAM32 multiplexer in the following ways:

1. The AM416 switches sixteen sets of fourlines at a time (4 x 16). The AM32 switchesthirty-two sets of two lines at a time (2 x 32).

2. The AM416 is packaged in an aluminumcase that should decrease temperaturegradients across the multiplexer terminalstrips.

3. The AM416 is smaller.

4. The AM416 contains terminals and circuitryfor sensor shield wires. This circuitry allowssensor shield wires to be routed through themultiplexer and grounded at the datalogger.

5. The packaging of the AM416 allows forstrain relief of lead wires on themultiplexer's case.

6. The AM416 contains diodes betweenshields and power ground for transientprotection.

Campbell Scientific Companies

Campbell Scientific, Inc. (CSI)815 West 1800 NorthLogan, Utah 84321UNITED STATES

[email protected]

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Somerset West 7129SOUTH AFRICA

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Thuringowa CentralQLD 4812 [email protected]

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CEP: 005543-000 São Paulo SP BRAZILwww.campbellsci.com.br

[email protected]

Campbell Scientific Canada Corp. (CSC)11564 - 149th Street NW

Edmonton, Alberta T5M 1W7CANADA

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Campbell Scientific Ltd. (CSL)Campbell Park

80 Hathern RoadShepshed, Loughborough LE12 9GX

UNITED [email protected]

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1, rue de Terre Neuve - Les Ulis91967 COURTABOEUF CEDEX

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08013 BarcelonaSPAIN

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Please visit www.campbellsci.com to obtain contact information for your local US or International representative.

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