Reading a thermocouple ?

I have a 6i25 connected to a 7i76

I want to read several thermocouples, the goal is to set use them in pid loops in the linuxcnc config

does anyone have a suggestion on what the proper approach to this would be ? I know I am going to need to put an amplifier on the thermocouples, and then I can encode the output from them however I want. I am looking for suggestion on how to go from amp output into the mesa space.

I know I can get rs422 from the 7i76, how hard would it be to read the data over serial that way ?

any suggestions would be great

Calvin

7i76 can have 4 inputs set as 8bit analog inputs, so that would be fairly easy to use. Or use Texas Instruments voltage to frequency converters and count them as encoders in 7i76, they are cheap but more work, and for this 7i77 might be more suitable .

The down side is that the 7i76 analog inputs are 8-bit, 36.3v full-scale and +-5% accuracy.

@calvin.d -- I don't think you can get the 7i76 RS422 interface to do what you want, but don't let that stop you trying.
Roger

It is possible to build firmware with a Packet-UART connected to the 7I76's RS-422 port
(normally this is used with a smart-serial module)
And I know there is at least preliminary driver support for the HM2 packet-UART
so its not impossible to communicate arbitrary data with a remote uprocessor in real time using this method

I am fine formatting the output and reading them as encoders, what is the proper mesa board to add if I just wanted 4-8 more encoder channels ?

I am guessing that this does not need to be fast?

I have used these with Arduino:
uk.rs-online.com/web/p/instrumentation-amplifiers/7861017/
(SPI interface, K-type conditioning, built-in cold junction)

A HAL module exists to bit-bang the SPI interface:
linuxcnc.org/docs/devel/html/man/man9/max31855.9.html

If you need higher speed then the Mesa BSPI module could be used. But the HAL module above can work on any GPIO including parallel port.