MC050-110 and 4-20 mA Inputs

[bryantmorris]

Hello all,

Is it possible to measure a 4-20 mA input on the MC050-110? I'm assuming you use the multi-function input but the configurations all seem to center around voltage inputs.

Any help you could provide would be great.

[Loader]

Hi,
this controller haven't current inputs!
You can use a current sensor putting a resistor and then measure the voltage...
Bye

[BRIan]

SCxxx, DP2xx, DP6xx and DP7xx have some current inputs. Otherwise see page 11 of 520L0931.

[FluidPowerTom]

An important note on the current inputs is that you can't have current going to the input pin until after it's started up.  This is because the pins don't configure themselves as current input pins until sometime during startup of the controller.  If you have your 4-20 mA sensor sending to the controller at startup then that input pin will go into a fault state thinking it detected a short.  Now I power any 4-20 mA sensors off of an output pin just to be sure.

[Morten Christensen]

Just convert the signal to a ~1-5 VDC signal with a 250 OHM resistor from GND to Signal. And then use a AIN input.

[oiltronic]

Bryantmorris, you can use a resistor in series with the current loop to create a voltage drop, but that only works if the negative side of the power supply of the sender & MC050 are the same.  The negatives could be different if there is distance between the sender & MC050, if they have different power supplies, or of hte power consumption between the two varies a lot. 

If there's a small voltage difference on the ground you could offset the voltage on the negative side of the resistor by putting a second resistor or diode in series, then use two inputs to measure the voltage difference across the main resistor.  Depends on how much you trust the sender.  Calculations left as an exercise to the reader.  If the sender and MC050 use different power supplies, just give up and get a signal conditioner to convert the current to a voltage.

[bryantmorris]

Thanks all,

I was able to just use 0-5 V sensors instead. I was just surprised the MC050 doesn't include current inputs when it seems to be a pretty common thing on the market these days. Maybe I just need to stick to CAN sensors.