AIO Module Range / Scaling Problem

[LozCool]

I have bought a RevPi Core 3+ and 2 AIO modules, and everything is fine.

But, the AIO spec says that a 4-20ma input (or other) is 16 bit. And the Outputs are 15 bit.

But, for example, I have to send (output 4-20ma) a value of 4000 – 20000 (integer) to the process image. This means I have a range of 16000. So, I lose 1 bit resolution on the output. Same, but worse, for inputs.

Does anyone know of a way that I can drive full scale to the ADC, DAC converters (0-65535, 0-32767) in the process image, please?

Thanks for your help, Loz.

[lukas]

The outputs are represented by a signed 16-bit value in piControl's process image (as are the inputs) and thus can accommodate a range of –32768 .. +32767. So you should be able to set values in the 4-20mA range directly.

If you need a different range such as 0 .. 65535, you may change the output's offset configuration in PiCtory. See the documentation for details.

If I misunderstood your question or haven't answered it sufficiently, please ask again. Thanks.

[->Johannes<-]

Dear Loz,

Yes, it is true that the resolution of 16 bit does not fit in the context of the selection options.

Range 4-20 mA => 16 mA => 16,000 µA => ~ 14 bit
Range 0-20 mA => 20 mA => 20.000 µA => <~ 15 bit
Range 0-24 mA => 24 mA => 24.000 µA => <~ 15 Bit
The resolution in the data sheet in mV, μA and K are correct so far.

The 16 bits are to be understood as up to 16 bits, the scaling is already done in the device.
The raw values cannot be accessed, except with the RevPi Compact.

Regards
Johannes