application note - acromag

Application Note:Math Modules: Flow Meter - Totalizing Effluent Plant Flow

Defining the Problem:

Scaling & summing up to four 4-20mA signals from flow sensors.

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Tel 877.214.6267 ■ [email protected] ■ www.acromag.com ■ 30765 Wixom Rd, Wixom, MI 48393 USA

Solution:

Model 894M-0500 quad-input math module Model 800C-SIP software interface package Optional: Model PS5R-VD24 power supply

ProductCategory

ApplicationIndustry

System Diagram:

Wiring Diagram: Scaling & Equation:

Output Equation:

MAX(A,0)+MAX(B,0)+MAX(C,0)+MAX(D,0)

When taking individual flow inputs offline (0 mA input), the “maximum” function will clamp that channel to a flow rate of zero (ie; 0 GPM), for calculation purposes.

Flow #1(0-100 GPM)

Flow #2(0-250 GPM)

Flow #3(0-500 GPM)

Flow #4(0-1000 GPM)

ABCD

Input

894M-0500+

-

Output

24V DC

Com 115V AC

4-20 mA

DCS/PLC/RTU/Chart Recorder

If flow sensors are loop-powered, thispower supply can be used to powerthe loops.The 894M-0500 hasinput-output-power isolation (3-way).

HOLD

4-20 mA

DC Power Supply - PS5R-VD24

0-1850 GPM

Hold Output(used optionally)

RLoad

Output = A+B+C+D

8401-004

Application Note:Math Modules: Flow: DP Totalizing - Effluent Plant Flow


Taking the square root and summing up to four 4-20mA signals from flow sensors.



Solution:

Model 894M-0500 quad-input math module Model 800C-SIP software interface package Optional: Model PS5R-VD24 power supply

ProductCategory

ApplicationIndustry

System Diagram:


Output Equation: SQRT (MAX(A,0))+SQRT (MAX(B,0))+SQRT (MAX(C,0))+SQRT (MAX(D,0))

When taking individual flow inputs offline (0 mA input), the “maximum” function will clamp that channel to a flow rate of zero (ie; 0 GPM), for calculation purposes.

Flow #1(0-100 GPM)

Flow #2(0-250 GPM)

Flow #3(0-500 GPM)

Flow #4(0-1000 GPM)

ABCD

Input

894M-0500+

-

Output

24V DC

Com 115V AC

4-20 mA


If flow sensors are loop-powered, thispower supply can be used to powerthe loops.The 894M-0500 hasinput-output-power isolation (3-way).

HOLD

4-20 mA


0-1850 GPM


RLoad

Output = A+ B+ C+ D

8401-005

D

Application Note:Math Modules: Flow: Dilution Percentage of Total Flow for Dosing


Transmitting the dosing percentage (ratio) of an additive based upon total flow of effluent.



Solution:

Model 892M-0500 dual-input math module Model 800C-SIP software interface package Optional: Model PS5R-VD24 power supply

ProductCategory

ApplicationIndustry

System Diagram:


Output Equation:(MAX(B,0)/(MAX(A,0)+MAX(B,0)+0.0000001))*100Using the “MAX” function quarantees that 0 GPM will be used for calculation purposes in the event of an open/shorted input fault (0 mA). The use of .0000001 in the denominator protects against a “divide by zero” condition.

Flow #2- additive(0-100 GPM)

Flow #1 - water(0-100 GPM)

B

892M-0500+

-

24V DC

Com 115V AC

4-20 mA


If �ow sensors are loop-powered, thispower supply can be used to power the loops. The 892M-0500 hasinput-output-power isolation (3-way).

HOLD


0-100%


RLoad Out = B

B+A

A

8401-006

Application Note:Math Modules: Level/Volume: Converting Linear Level to Tank Volume


Convert a 4-20mA level signal (proportional to height) to a 4-20mA signal proportional to volume.



Solution:

Model 892M-0500 dual-input math module Model 800C-SIP software interface package Optional: Model PS5R-VD24 power supply

ProductCategory

ApplicationIndustry

System Diagram:


Output Equation: (((((A-24)*SQRT((48*A)-(A*A)))+ ((576)*ASIN((A-24)/24)+(904.77868))*129)/231)* 0.9896

The volume equation above uses a final “multiplier” of 0.9896. This is used for full-scale “trimming” purposes. Without the multiplier, the calculated/theoretical output at full-scale is 1010 gallons. Also, a level tank is assumed for this example.

B

892M-0500+

-

24V DC

Com 85-260 AC

4-20mA

DCS/PLC/DAQ

HOLD


0-1000 gallons


RLoad Out =

A

r

L

h

n.c.

Level sensor (2-wire output)4-20mA

Input Output

Volume(gallons)

Volume (gallons) = (((x-r) 2rh-h2 + rsin -1 ( h-rr ) + r2

2)* L)/231

Where: r = radius (inches) L = length (inches) h = variable height (inches)Conversion: 231 inches3 = 1 gallon

π

= 3.141593π

(0 - 48")

Tank Style: Horizontal cylindrical tank with �at sidesTank Volume: 1000 gallons nominalTank height (h) = 4'Tank radius (r) = 2'Tank length (L)= 10'9"

Standard equation for horizontal tank

8401-007

*The 892M moduleshave a track & holdfeature that will holdthe output indefi-nitely. This is useful during service & maintenanceof systems.

Application Note:Math Modules: Monitoring RTDs for Temperature DifferentialDefining the Problem:

Monitor three RTD’s on a stack and transmit two differential 4-20mA signals representing -7 to 18°F. Each RTD transmitter is calibrated -20 to 120°F.

RUNAcromag

MODE

Z/FS

ST

SET

R

RLY

RUNAcromag

MODE

Z/FS

ST

SET

R

RLY

TB 1

TB 3

111213141516

313233343536

TB 1

TB 3

111213141516

313233343536

Inputs InputsVIRTNVIRTN

VIRTNVIRTN

Output OutputDC+DC-RTN

IO +

-RL4-20mA

DC+DC-RTN

IO +

-RL4-20mA

Outputs

RTD 3+

-

RTD 1(reference)

+

-

RTD 2+

-

4-20mA (-20-120°F)

4-20mA(-20-120°F)

4-20mA(-20-120°F)

24V DC



Solution:

Model 892M-0500 math module (qty. 3) Model 800C-SIP software interface pkg. (qty. 1) Model PS5R-VD24 power supply (qty. 1)

ProductCategory

ApplicationIndustry

System Diagram:


Output Equation: A - B

892M-0500 +

-

24V DC 85-260V AC

4-20mA

DCS/PLC/RTU

RLoad

4-20mA(-20-120°F)

Output

Output

Out = A - B

892M-0500 +

-

4-20mA

RLoad

B

892M-0500 +

-

4-20mA

RLoadA

B

A

Out = A - Bxxx.x

xxx.x

xxx.x

RTD 3

RTD 2

RTD 1 (ref.)

4-20mA(-20-120°F)

4-20mA(-20-120°F)

(-7 to 18°F)

(-7 to 18°F)Model PS5R-VD24

8401-008

Model No: 892M-0500Tag No: RTD3-RTD1Input: 4-20mAOutput: 4-20mA (-7 to 18°F)

Model No: 892M-0500Tag No: RTD2-RTD1Input: 4-20mAOutput: 4-20mA (-7 to 18°F)

Application Note:Math Modules: Flow: Instantaneous Flow of a V-notch WeirDefining the Problem:

Calculate the discharge rate Q (g.p.h.) output of a V-notch weir. Provide a 4-20mA output for flowrate and frequency output for totalization and alarm output for high-level alarm.

RUNAcromag

MODE

Z/FS

ST

SET

R

RLY

RUNAcromag

MODE

Z/FS

ST

SET

R

RLY

TB 1

TB 3

111213141516

313233343536

TB 1

TB 3

111213141516

313233343536

Inputs InputsV1+Il+RTNV2+I2+RTN

V1+Il+RTNV2+I2+RTN

TB 2212223242526

SWSW

Output OutputDC+DC-RTN

IO

DC+DC-

TB 4414243444546

PUL1FRQ1COM

-+

Leveltransmitter

4-20mA

24V DC

24V DC

+-

0-5400counts perhour (C.P.H.)



Solution:

Model 892M-0500 DC output math module Model 895M-0800 freq. output math module Model: 800C-SIP software interface package Optional: Model PS5R-VD24 power supply

ProductCategory

ApplicationIndustry

System Diagram:


Output Equation: (1.4249885*POWER(A+.0036961743,2.5))*26929.87

The equation above calculates discharge rate Q (g.p.h.) based on the level (height) measurement on input A. The “power” function shown raises “A+.0036961743” to the “2.5” power.

h

p

B

water�ow

892M-0500

895M-0800

End View

Discharge Rate: Q(g.p.h.)= (4.28C tan 2( ) (h+k)5/2)*26929.87

4-20mA (0 - 1 ft.)

DCS/PLC4-20mA

Analog Input

Counter Input(totalizer)

85-260V AC

PS5R-VD24

24V DCAlarmContact

A Output = 0 - 5400 C.P.H.

AOut = 4-20mA(0-54000 G.P.H.)

Reference: www.LMNOeng.com/Weirs/vweir.htm

Q (g.p.h.)

V-notch weir: Find Q (g.p.h.)Notch angle, = 60 degreesHead, h = 0 to 1 ft.Discharge coe�cient, C: 0.5766711Head Correction Factor, K (ft.): 0.0036961743Channel, B (ft.): 8 ft.1 ft. 3/sec = 26,929.87 g.p.h.

LevelSensor

8401-009

Model No: 892M-0500Tag No: Level InputInput(s): 4-20mAOutput: 4-20mA

Model No:895M-0800Tag No: Q InputInput: 4-20mAOutput: 0-5400 c.p.h.Alarm: High limit 20mA

application note - acromag

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