+/- 10V to 4-20mA converter

[Mogaraghu]

I have a amplifier which has an input of 4-20mA for command.

I have a signal source which is capable of only -10V to + 10V.

I want a converter in between to convert the input as below :

- 10V input  : 4mA output

0V input : 12mA output

+10V input : 20mA output.

Any suggestions ? Circuits ??

Thanks in advance.

[jackrae]

I think you'll need to tackle this problem in two stages.
First you need to convert your -10 to +10 volt signal to a level suitable for simple conversion, say 1 to 5 volts
Once you have the 1 to 5 volts you can then use a simple V to I conversion such as the attached diagram.

[sdturner]

If you prefer programming, get an ADC that can read +/- 10V, read it with an Arduino, then get a 4-20mA driver IC, something like the AD5749 or similar. Depending on the speed and number of channels probably any low end Arduino should be capable.

If you prefer analog then you will need a bipolar supply (+/- 12 or 15V) and probably two stages of level shifting circuit. You might be able to do it all one stage, but I'd have to go through the design process to figure out how to do it. It's probably easier to shift the signal to 1-5V and then use a 4-20mA driver circuit.

[tauro0221]

Hi,
"signal source which is capable of only -10V to + 10V"  Is this is a home made or it is a commercial product?  Can you right down the model and who make it?

[Mogaraghu]

Thanks for all the suggestions.

As mentioned by jackrae I have solved the problem by a initial Bipolar ( +/-10) to unipolar (0-10) convertor and then using a standard ICP-DAS voltage to current convertor. Its working.

I am glad this forum has talents at various domains.

[Mogaraghu]

Hi,
"signal source which is capable of only -10V to + 10V"  Is this is a home made or it is a commercial product?  Can you right down the model and who make it?

This is a output from a Analog data acquisition card from National Instruments. Model PC1-6229.  Outputs +/- 10V with 16 bit resolution.