Converting Amperage to Voltage

Product or schematic for PLC analog voltage input card. Converting DC amps to Dc voltage. Example
I have a hydraulic proportional valve drawing between 0 to 2 amps. My PLC has a 1-10 volt analog input card. How can I convert the amperage to voltage so that I can scale this into the PLC?

The simple answer is putting a resistor in series because V=I*R, however, you have to figure out what scale you want. For example, if you wanted the full 10V range, that would require a resistance of 5Ohms based on the maximum amperage. The issue is that the load changes because of the added resistance. Another way of doing what you desire is to have some kind of current sensor capable of reading at least 2A. The output tends to be in the millivolt or volt range though, so you kind of have to look around for different current sensors on Digi-Key’s site. If you only find ones that output millivolts, you can amplify that using a Operational Amplifier.

If you have a solid range you could use CR5211-2-ND (Special order at time of posting ~5 week turnaround); that would get you 0-2Amps with a Ratio out of 10V.

If you believe in your PLC and get good accuracy and need a part today? The 10A version can be seen here: CR5211-10

Of course, review the datasheet before making the jump and reference you specifics on the PLC you are using.

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