Differential Signal to Single Ended Signal Conversion

[Arvel]

Hi,

Im facing a problem here. I need an ADC that reads 0-20mA. The signal comes from a signal conditioner that creates a differential signal. However, a NI device with single ended inputs is much cheaper than differential inputs.
The signal conditioner already exists and I cant change that.
Im looking for something that can convert the differential signal to a single-ended signal.
I tried finding an IC that does that, but couldnt find one. Do they exist?
Maybe its easier for voltage than for current.

How is this usually done?

Best regards,

Arvel

[df86]

A differential signal normally relates to voltage measurement. Voltage reference to potential buildup therefore you need to compare that potential build up to a reference source. On a single ended signal, the reference is Ground. On a differential signal, the reference is an additional input.

Now a 0-20mA signal is measuring current not voltage. Therefore there is no such a thing as a differential 0-20mA signal. Current flow, just like any other type of flow (water), needs a source and a sink. the reason you have two lines is so that the current can flow through the sensor from one input to the other. That's why you can't find an IC that converts a differential mA singal to a single ended because there is no such a thing.

Hope this helps,

[crossrulz]

Use a current sensing resistor and then use a current shunt amplifier.  The amplifier will amplify the voltage drop across the reistor.  From there, you can just read the output voltage with a DAQ.  Create a DAQmx scale to do the math to convert that voltage into a current reading.

[Arvel]

Shouldnt it be possible to have to current flow back through the Ground?
Actually I already figured out I can set the amplifier to voltage output instead of current.

Anyway, thank you very much for your answers!

[df86]

depends on the device that's outputing the current. If it has a dedicated output line then yes, most likely you should be fine.

Glad to hear it's working. Just keep in mind that the advantage of using current vs Voltage signals is the higher level of immunity for noise.

Dan,