Current Signal Conditioner
- Thread starter fifty60
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Spoke too soon. Found something here:
http://www.omega.com/pptst/CCT.html
They seem to only take AC current...nothing for DC current?
http://www.omega.com/pptst/CCT.html
They seem to only take AC current...nothing for DC current?
winnie
Senior Member
- Location
- Springfield, MA, USA
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- Electric motor research
Take a look again at the omega catalog. If they don't have a signal conditioner that will take the current range you need, they will have one with a mV input that you can use with an appropriate current shunt.
If you can't tolerate the current shunt, then use an active hall effect current transducer (essentially a current transformer for DC) and then put a suitable burden resistor on the output of that, and use the mV conditioner to convert the voltage across that resistor to your 4-20mA output.
_Or_ if you can tolerate homebrew, it is pretty trivial to use an active hall effect current transducer and an op-amp or 2 to provide the 4-20 mA output.
-Jon
If you can't tolerate the current shunt, then use an active hall effect current transducer (essentially a current transformer for DC) and then put a suitable burden resistor on the output of that, and use the mV conditioner to convert the voltage across that resistor to your 4-20mA output.
_Or_ if you can tolerate homebrew, it is pretty trivial to use an active hall effect current transducer and an op-amp or 2 to provide the 4-20 mA output.
-Jon
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
You may not find a DC current in that range, but you can use a shunt and a DC millivolt input.
To convert 2A to 100mv you would need a precision 0.05 ohm shunt resistor.
The power rating would only have to be half a watt (actually less than 1/4, but you get better accuracy if you keep the temperature down.)
Presumably the 100mv voltage drop across the shunt will not be a problem.
If you are not too concerned about zero drift you could also use a Hall Effect sensor with a DC voltage output.
To convert 2A to 100mv you would need a precision 0.05 ohm shunt resistor.
The power rating would only have to be half a watt (actually less than 1/4, but you get better accuracy if you keep the temperature down.)
Presumably the 100mv voltage drop across the shunt will not be a problem.
If you are not too concerned about zero drift you could also use a Hall Effect sensor with a DC voltage output.
gar
Senior Member
- Location
- Ann Arbor, Michigan
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- EE
151104-2030 EST
fifty60:
Take a look at http://www.lem.com/docs/products/la 55-p e.pdf . This is a null balance system with isolation, good zero stability, linearty, and bandwidth. Use 25 turns for 2 A full scale. Resolution and drift are good over a wide temperature range. Use an external device to convert to 4-20 mA. LEM or other manufacturers may have a direct output to 4-20 mA.
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fifty60:
Take a look at http://www.lem.com/docs/products/la 55-p e.pdf . This is a null balance system with isolation, good zero stability, linearty, and bandwidth. Use 25 turns for 2 A full scale. Resolution and drift are good over a wide temperature range. Use an external device to convert to 4-20 mA. LEM or other manufacturers may have a direct output to 4-20 mA.
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