- #1
gpsimms
- 30
- 1
Hey Everybody,
So we have a PID heating system with K-type thermocouples running through labview. We have a chassis that has 6 DAQ cards for Tc inputs (2 daq cards), flowcontroller in/out, an output for the heating elements for the PID control, and another input for a pressure transducer.
Anyway, the thermocouples give nice reading at most temperatures near room temperature. And the PID system seems to work, as I can control temperature pretty closely in the 300K-800K range. However, when I get to 800K+, some (not all) of the thermocouple readings go kind of nuts. They might randomly spike up to 1200K in a second, and then come down to 400K, etc. If I turn off the heating, after enough time passes and things have cooled back down, they might start behaving normally again.
I have all the DAQ cards coms wired together and then sent together to ground. Is this more likely to be a wiring/grounding issue or is it likely some sort of programming/labview issue? I don't suspect the problem is with the Tc's, as they are pretty new. I have no background at all in circuits, so I kind of think it is most likely something I am doing wrong, but I have to admit, when someone says "It's probably a grounding issue," I don't really understand what exactly that means or how I should ground it differently.
Sorry if this is a really basic question, but I guess this is what happens when a mathematician tries to like, actually do stuff.
Thanks!
simms
So we have a PID heating system with K-type thermocouples running through labview. We have a chassis that has 6 DAQ cards for Tc inputs (2 daq cards), flowcontroller in/out, an output for the heating elements for the PID control, and another input for a pressure transducer.
Anyway, the thermocouples give nice reading at most temperatures near room temperature. And the PID system seems to work, as I can control temperature pretty closely in the 300K-800K range. However, when I get to 800K+, some (not all) of the thermocouple readings go kind of nuts. They might randomly spike up to 1200K in a second, and then come down to 400K, etc. If I turn off the heating, after enough time passes and things have cooled back down, they might start behaving normally again.
I have all the DAQ cards coms wired together and then sent together to ground. Is this more likely to be a wiring/grounding issue or is it likely some sort of programming/labview issue? I don't suspect the problem is with the Tc's, as they are pretty new. I have no background at all in circuits, so I kind of think it is most likely something I am doing wrong, but I have to admit, when someone says "It's probably a grounding issue," I don't really understand what exactly that means or how I should ground it differently.
Sorry if this is a really basic question, but I guess this is what happens when a mathematician tries to like, actually do stuff.
Thanks!
simms