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Process signal (0-20mA) converter - input and output 2
- Thread starter csgasbm
- Start date
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1
- #2
I do not, off hand, know of one. But check Omega.com
Also you could use a regular temp/etc controller. Drop a resistor across your 0-40mA which converts the 0-40mA to a voltage. Then using the linear input of a controller, scale the 0-40mA(now a voltage). The controller can sit there trying to control 'nothing'. Just make sure you get a controller that has a 0-20mA or the more normal 4-20mA output(option) to provide your 'converted' output.
You can use the resistor to do linear mods and also the controller. If you want some strange (non-linear) transformation...
Keith Cress
Flamin Systems, Inc.-
Also you could use a regular temp/etc controller. Drop a resistor across your 0-40mA which converts the 0-40mA to a voltage. Then using the linear input of a controller, scale the 0-40mA(now a voltage). The controller can sit there trying to control 'nothing'. Just make sure you get a controller that has a 0-20mA or the more normal 4-20mA output(option) to provide your 'converted' output.
You can use the resistor to do linear mods and also the controller. If you want some strange (non-linear) transformation...
Keith Cress
Flamin Systems, Inc.-
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1
- #4
To elablorate on Keith's suggestion:
Use a couple precision 250 ohm resistors in parallel (250 precision resistor are readily available from instrumentation suppliers) in order to convert the signal to 0-5Vdc.
Use a mid level PID controller or high level digital indicator with a re-transmitting output which can handle the 0-5Vdc input, do some conversion math on the input and re-output the input on its 4-20mA control output.
Mid level single loopers, like Honeywell UDCs have a Y=mx+b: multiply by a ratio factor, offset by a bias.
specsheet:
The high end UDC3500 one has an 8 point look up table capability or polynomial function:
- 8 Segment Characterizers – Two 8-segment characterizers are available that can be applied to any analog input, to Loop 1 Output or to Loop 2 Output. These can be linked together to produce a single 16-segment characterizer.
- Polynomial Curve Characterizer – A fifth order polynomial equation can be used on any one of the analog inputs.
spec sheet
Precision Digital 690 has a look-up table and a 4-20 retransmit option
spec sheet:
Use a couple precision 250 ohm resistors in parallel (250 precision resistor are readily available from instrumentation suppliers) in order to convert the signal to 0-5Vdc.
Use a mid level PID controller or high level digital indicator with a re-transmitting output which can handle the 0-5Vdc input, do some conversion math on the input and re-output the input on its 4-20mA control output.
Mid level single loopers, like Honeywell UDCs have a Y=mx+b: multiply by a ratio factor, offset by a bias.
specsheet:
The high end UDC3500 one has an 8 point look up table capability or polynomial function:
- 8 Segment Characterizers – Two 8-segment characterizers are available that can be applied to any analog input, to Loop 1 Output or to Loop 2 Output. These can be linked together to produce a single 16-segment characterizer.
- Polynomial Curve Characterizer – A fifth order polynomial equation can be used on any one of the analog inputs.
spec sheet
Precision Digital 690 has a look-up table and a 4-20 retransmit option
spec sheet:
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