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

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 ?

if you just need frequency reading you just need 1 pin per channel (the encoder "A" signal)
so you dont really need 4 or 8 more encoder channels (8 encoder channels is 24 signals)
for example if you have a 6I25, you could have a config that used the second 6I25 connector
as 17 encoders all with just channel A brought out

ok so one config I was thinking of may require another 7I76 to get another stepper motors for what I am thinking

can I setup the second 7I76 inputs to encoders and just break out the A channel as suggested ?

if that is the case what is a good input scheme for the thermocouple output. I am going to put a micro controller between the thermocouple and the 7I76.

so if I want a 0-600C range for temp
what is a good frequency range to map that too ?

ideally I want to plug this into a PID loop in linuxcnc and control the temp that way

Thanks for all of the suggestions

C

If you just need more step motor outputs a second 7I76 is overkill, you could use a 7I85S and gain
4 additional stepper outputs and 12 inputs

Any frequency from a few KHz to maybe 1 MHz or so should be OK

An all "A" encoder connection would require custom firmware but its a pretty simple change