Thermocouple output fed into two devices

[AnalogKid2DigitalMan]

I'll research on my own, but thought I'd post here in case anyone has had similar needs/solutions.

We have an extruder that we'd like to monitor and log data on. The majority of the signals are J and K type thermocouples that are fed into PID temperature controls. Unfortunately the PID controllers do not have retransmitter analog ouputs to scale the readings into V or mA. That would have been very convenient to interface to the appropriate DAQ hardware.

Thus, is it possible to connect a thermocouple input based DAQ to the same thermocouple inputs to on the PID controllers without affecting the signal? One thermocuple feeding two inputs- one to the PID, the other to the DAQ. I do not have the input specs yet for the PID controllers, presume the are >1Mohm. I would be using the appropriate thermocuple wire type as needed.

Thanks

-AK2DM

[Henrik_Volkers]

Once I saw a box to do it. It was custom made (with some nice OPs and lots of thoughts on how to avoid parasitic thermo emf)  to deal with µ-Volts provided by the TCs (and adds only about 2K additional error...)

However the only correct way I can think of, is to use a TC conditioner with CJ and an 'regular' output (20mA/X-Volt) that is capable to feed two inputs. Most controls can be configured to read theses standard outputs instead of a TC.

[AnalogKid2DigitalMan]

Henrik:

Thanks for the advice, your sentiements are pretty much echoed in Omega's technical sections. Bummer, looks like retransmitters or 4-20mA converters are in store.

Thanks

-AK2DM

[Brian_Beal]

I have seen this done many times, without ill effect.  Just piggyback them together and you should be OK as long as the inputs are meant to take in thermocouples.

[Russ@Davis]

I have also seen piggybacked connections used successfully.  With that said, these applications could tolerate error of ±20°F  -- You ARE introducing error in the signal.