need amplifier circuit for M831 Electronic YZC 131 5kg weighing weight scale pressure sensor load ce

[balajiraja457]

We need to convert load cell output(millivolt) to (4-20)milliamps to give input to the PLC. Is there any IC or circuit diagram to directly convert millivolt to milliamps?

 

[ericgibbs]

hi 457,
Th AD694 will give a 4 to 20mA output, you may need to amplify the sensor output first.
E

 

[balajiraja457]

thank you for your suggestion.. but We already have an idea about v to i converter... can you please give us a suggestion about how to amplify 1mv to (0-5)v? We already tried some circuits for amplifying loadcell output. but we didn't get the related output. If you have any circuit about that, please give us suggestions..

 

[ericgibbs]

hi 457,
This is one option, using a AD623 Inst Amp.
This sim IA is set for 0 to 2v Out
E

EDIT:
This is the information I have for your sensor.
Specification:

Model: YZC-131A
Dimensions: 75x12.7x8mm/2.95 x 0.51 x 0.31"(L x W x H)
Range: 5 kg
Rated Load: 2 kg
Rated output: 1.0 ± 0.1mV / V
Nonlinear: ± 0.05% F.S
Hysteresis: 0.0% F.S
Repeatability: 0.05% F.S
Creep (5 minutes): 0.05% F.S
Temperature Effect on Output: 0.003% F.S /°C
Zero output: ± 0.2 mV / V
Input impedance: 1050 ± 10% ?
Output impedance: 1000 ± 10% ?
Insulation resistance: ?2000 M?
Operating temperature range: -21 ~ 40°C
Recommended for: kitchen scales
Weight:21g

 

[balajiraja457]

hi ericgibbs,
Thank you for your suggestion. With this circuit, can we interface directly loadcell with PLC? The output of the circuit should be vary within 4-20milliamps corresponding to the load cell input. For example, If the load cell input is zero means the output of the circuit must be 4milliamps. Is this possible with this circuit?

 

[balajiraja457]

Is this circuit require only one AD623? or three AD623?

 

[ericgibbs]

hi 457,
It is just one AD623, the dotted rectangle around the circuit encloses the internals of aAD623.

Eric

 

[balajiraja457]

Thank you Eric.
With this circuit, can we interface directly loadcell with PLC? The output of the circuit should be vary within 4-20milliamps corresponding to the load cell input. For example, If the load cell input is zero means the output of the circuit must be 4milliamps. Is this possible with this circuit?

 

[ericgibbs]

hi,
Do you mean the Load Cell > AD623 > PLC.?? type connection?
or
LC >> PLC.?

Please post details of the PLC if its option #2.

E

 

[balajiraja457]

We mean (Load cell > AD623 > AD694 > PLC) this type of connection.
PLC model is Allen Bradley compactlogix L32E.

 

[ericgibbs]

We mean (Load cell > AD623 > AD694 > PLC) this type of connection.
PLC model is Allen Bradley compactlogix L32E.

hi 457,
Looking at the PLC specification I do not see a 4-20mA or Analog voltage input option.??
Please confirm.
E

 

[balajiraja457]

In this circuit, What is the (.tran 0 1 0 1m) circuit? The supply voltage for pin7 and 4 is 8v, isn't it?

 

[balajiraja457]

We use controller 1769-IF8 & we connect the I/Os to 1769-IF8. It accept 4-20ma. So there is no problem about that. We decide to use the circuit that you suggested.

 

[ericgibbs]

We use controller 1769-IF8 & we connect the I/Os to 1769-IF8. It accept 4-20ma. So there is no problem about that. We decide to use the circuit that you suggested.

hi,
The AD694 should drive the 1769-IF8 input 4mA to 20mA OK.

E

 

[balajiraja457]

That's Fine. Thank you so much for your help eric. If we have any doubt during execution, we will ask you...

Balaji.

 

[balajiraja457]

In this circuit, What is the (.tran 0 1 0 1m) circuit? The supply voltage for pin7 and 4 is 8v, isn't it?

 

[balajiraja457]

hi, Can you please tell us the pin connection of AD694. Also we have a doubt in AD694 connection. Is that enough to give the AD623 output to AD694? or any external connection is needed?

 

[ericgibbs]

In this circuit, What is the (.tran 0 1 0 1m) circuit? The supply voltage for pin7 and 4 is 8v, isn't it?

hi,
The .tran is only for LTS simulation
AD623 pin #4 is 0V and pin#7 is +8v.

For the AD694 look at page #9 Fig8. that is the circuit for a 0v thru 2v analog input voltage.
Pin#11 is the AD694, 4mA to 20mA output and should be connected directly to the 1769-IF8 4mA to 20mA input.

I assume the 1769-IF8, 4 to 20mA input have an inbuilt load resistor, typically in the order of 250 Ohms.?

E

 

[balajiraja457]

Hi eric,
We got output from AD623 in the range of 0.5 to 1 v. But we can't get (4-20 ma) output from AD694. We made a connection as per the following circuit diagram. But we give 24 v supply and 10 micro farad. We get maximum output of 0.04 ma.we didn't add load resistor. Is this necessary to connect the load resistor b/w 11 & 5? What is your suggestion to get (4-20 ma)?

 

[ericgibbs]

hi 457,
It is required that you follow the design instructions from the d/s when using a single supply and 0v to2V input range, ref this image.
Connect an Ammeter from pin #11 and 0V, this should show a 4mA thru 20mA for a 0v to 2v test input voltage,
Adjust Ra variable resistor to get the required span.
E