PT100 With an AI 8xRTD/TC 2-wire HF card

Dear Experts,

I have a problem reading out the value of a PT100 Endress+Hauser TMR31 with an AI 8xRTD/TC 2-wire HF card (6ES7 134-6JF00-0CA1).

Regards,

Stephane

Do you have the M12 connector / cable configured like this:

Pin 1: 10-35VDC (BN) 4-20mA
Pin 2: PC Configuration cable (WH)
Pin 3: 0VDC (BU) 4-20mA
Pin 4: PC Configuration cable (BK)

or like this:

Pin 1: TC+
Pin 2: TC+ sense
Pin 3: TC- sense
Pin 4: TC-

Does your device have a built in transmitter?  If so, then first wiring scheme.

It is in the documentation you posted images from. 

Hey Huggy_d1,

Thanks for the reply!

I have a (stupid) question, does the RTD card sends out a value between 0...27648 or a value in temperature (divide by 10)?

Grtz,

RTD modules are typically configurable to how much precision (1 or 2 implied decimals) you want.

But yes, if you have an RTD or TC module, the actual value times 10 to the required # of decimal places is what is presented at the IW# for the input.  It is in the manual for the module.

Stephane202

Hey Huggy_d1,

Thanks for the reply!

I have a (stupid) question, does the RTD card sends out a value between 0...27648 or a value in temperature (divide by 10)?

Grtz,

Hey Huggy_d1,

Thanks for the reply. 

Yes, i've read the manual. I think i missed it.

Now, i read a value that has an offset of +- 2 degrees. Any idea? 

Regards,

The analog input sensing side connected to a 2 wire RTD cannot tell the difference between wire resistance and the temperature element resistance.  

An analog input that is configured for a 2 wire RTD will ALWAYS see a positive offset error above the true temperature value because of the added resistance of the copper connecting wire.  The magnitude of the error depends on the resistance of the copper lead wire and the AI calibration.

3 or 4 wire RTD connections compensate for lead wire resistance.  A 2 wire RTD circuit does not and cannot compensate for lead wire resistance.

The temperature error offset should be constant for practical purposes.  Just subtract out the offset.

Hey Danw,

Thanks for the clear answer!

Regards,