4-20ma PLC Input Only Reading Lower Half of Range

2020-02-27T22:31:33.510000Z

Yep, it was a hardware issue. The PLC input had a resistance that was too high for the sensor.

4-20ma PLC Input Only Reading Lower Half of Range

2020-02-27T22:31:31.934000Z

as you can see in PLCS.net it is a hardware problem, as the sensor is not able to send a signal above 4 volts (strange but cheaper.

4-20ma PLC Input Only Reading Lower Half of Range

2020-02-27T22:31:27.511000Z

Hi everyone,

I've attached a 4-20ma level sensor to a PLC input that is configured for current. The PLC reads the range 4-12ma just fine, but anything from 12-20ma is just read as 12ma by the PLC. I'm using an IFM CR0232 (http://www.ifm.com/products/ca/ds/CR0232.htm) with Codesys 2.3, and the sensor is a Turck Inclinometer (http://old.turck.us/illustrations/M1...0(sheet_1.pdf).

I did some measuring with the meter, and the sensor is indeed putting out 4-20ma. I also checked voltage, and the sensor outputs between 1.55 volts (when the sensor is putting out 4ma) and 4.55 volts (when the sensor is putting out 12ma). The voltage remains the same at 4.55 volts from 12-20ma.

The code is very simple, using an IFM library block:

VAR_INPUT
  xChannelNumber:BYTE;(*Channel number for the X angle*)
END_VAR
VAR
  xInputAnalogBlockExtended:INPUT_ANALOG_E;      (*Input block for extended input, X*)
  xTempWord:WORD;
  xError:BYTE;
END_VAR
xInputAnalogBlockExtended(
      ENABLE:=TRUE,
      MODE:=IN_CURRENT,       (*Global constant defined in library*)
      CHANNEL:=xChannelNumber, (*Integer input*)
      OUT=>xTempWord,
      ERROR=>xError);

Any ideas?
Thanks!

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