Peter Nachtwey
Member
I am sure there are plenty of people here that have used Watlow temperature controllers.
We have a thermal chamber that we used to temperature stress circuit boards.
The thermal chamber heats to 85 degrees C. It can go higher. Then it cools to -20 degree C. Again it can go higher. This must be done a certain rates but that is another issue.
The problem is that we lost the parameters. I got the controller going again but the documentation was awful. Not just bad but awful. A P gain should be %output/degree of error. If the gain is a proportional band I expect a number like degrees/100% output. Instead the Watlow seems to be degrees per 1% output.
There can be two sets of PID parameters. One for heating and one for cooling. It appears that the parameters for the cooling PID are set to 0. If so, I assume that I am using the same PID parameters for both heating and cooling.
Is my assumption correct?
Also, our P gain is set to 2.7. I am assuming that means 1% output for every 2.7 degrees of error.
Is my assumption correct?
We set the I gain to 1. We couldn't figure out if this was repeats per minute or minutes per repeat. There seems to be a way of changing between the two modes but we couldn't find it in the documentation.
What is a repeat? What is being repeated? When I am doing temperature PID calculations for PLC PIDs the integrator is usually a time constant, not a repeat.
We have talked about replacing the Watlow with our motion controller. It would be gross overkill but at least we have good documentation and understand how it works.
We have a thermal chamber that we used to temperature stress circuit boards.
The thermal chamber heats to 85 degrees C. It can go higher. Then it cools to -20 degree C. Again it can go higher. This must be done a certain rates but that is another issue.
The problem is that we lost the parameters. I got the controller going again but the documentation was awful. Not just bad but awful. A P gain should be %output/degree of error. If the gain is a proportional band I expect a number like degrees/100% output. Instead the Watlow seems to be degrees per 1% output.
There can be two sets of PID parameters. One for heating and one for cooling. It appears that the parameters for the cooling PID are set to 0. If so, I assume that I am using the same PID parameters for both heating and cooling.
Is my assumption correct?
Also, our P gain is set to 2.7. I am assuming that means 1% output for every 2.7 degrees of error.
Is my assumption correct?
We set the I gain to 1. We couldn't figure out if this was repeats per minute or minutes per repeat. There seems to be a way of changing between the two modes but we couldn't find it in the documentation.
What is a repeat? What is being repeated? When I am doing temperature PID calculations for PLC PIDs the integrator is usually a time constant, not a repeat.
We have talked about replacing the Watlow with our motion controller. It would be gross overkill but at least we have good documentation and understand how it works.