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Evenheat too hot in the back?
- Thread starter Tenebr0s
- Start date
They didn't say... but we're still working on the issue.
My (educated) guess at this point is that the ramp rate simply calculates the set point temperature, and the PID loop tries to match it. So if the PID parameters are right, it will not overshoot (too much), regardless of the ramp setting.
Now that's the way it should work, but:
1) The thermocouple in the oven is shrouded in a ceramic sleeve except at the very tip. This adds a significant time delay to the measurement. In practice the actual temperature overshoots even if the controller measures a very stable approach to temperature.
2) Changing the TC to an arrangement with a lower time constant throws the (TAP) controller out of whack, and it goes into error mode after detecting it has gone too far.
3) Even when using the solid state relay, the controller does not make use of it, and switches at a frequency of ~4 seconds. This limits how little overshoot you can have, especially at low temperatures.
My (educated) guess at this point is that the ramp rate simply calculates the set point temperature, and the PID loop tries to match it. So if the PID parameters are right, it will not overshoot (too much), regardless of the ramp setting.
Now that's the way it should work, but:
1) The thermocouple in the oven is shrouded in a ceramic sleeve except at the very tip. This adds a significant time delay to the measurement. In practice the actual temperature overshoots even if the controller measures a very stable approach to temperature.
2) Changing the TC to an arrangement with a lower time constant throws the (TAP) controller out of whack, and it goes into error mode after detecting it has gone too far.
3) Even when using the solid state relay, the controller does not make use of it, and switches at a frequency of ~4 seconds. This limits how little overshoot you can have, especially at low temperatures.