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M91 Analog Input 4-20ma not reading correctly

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Im having an issue with a M91-2-r2-c Analogue input raw values.

I have set jumpers 3 and 4 to B and have configured software for 4-20ma. On 4ma on multimeter I get a raw value in my MI register of 9, and 20ma I get 45.

I also changed M91 and software to 0-10v with the same outcome with the raw values. I have been using a signal generator to mimic these values.

This is the first time I have used these 91s on Analog and are wondering if I have missed something or the unit is faulty.

Thanks for any assistance.

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Your jumper settings seem fine and you said you have set the hardware setting On the U90 software for 4-20ma so that all seems correct. Since you are using an external signal simulator to generate the 4-20/0-10VDC analog, if you are using a generator that is generating its own loop power, have you connected the negative side of this simulated signal to the 0V terminal of the U91 and the positive side of your simulator to AN0? If you are using a simulator that does not supply its own loop power then you need to connect the + side of your simulator to the +V terminal of the PLC and the negative side of your simulator to AN0 to get a usable 4-20ma signal into the PLC.



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  • 2 weeks later...

Thanks for your help.

We ordered another one, and you were right on with the signal generator. I was using it incorrectly as I was connecting it the same as the 2 wire transducer but it was self powered. The first unit was faulty as the second unit when installed operated correctly.



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