Operation with the Flux Controller
TIP: To improve stability try manually increasing the Proportional Band (Pb) setting in
the PID parameter list to values around 600.
4.4.4 PID and Controller Parameters
It may be necessary to adjust the PID parameters to ensure optimal control. It may also
be necessary to repeat this process if the flux is significantly changed. Follow the in-
structions in the PID controller manual to allow the controller to perform its autotuning
function.
For the best control it is important to set the maximum output voltage of the PID con-
troller to be only slightly higher than that needed to achieve the filament current re-
quired for the desired operating conditions. Otherwise when the controller is perform-
ing its autotuning function it may significantly overshoot the required operating condi-
tions.
This can also be achieved by adjusting the potentiometer (nearest to the black heatsink)
on the filament triac board in the power supply so that at full PID controller output, the
filament current is only slightly higher than that needed to achieve the required evap-
oration rate.
4.4.5 Safe operation tips
The current control on the HV supply can be used as an emission current limit. If before
going to auto control this is adjusted to be just above the emission current level re-
quired (the volts will be seen to drop once the current limit is set too low) then this will
prevent the emission current from rising to excessive levels.
Similarly on the PID controller by pressing page 6 times “OP list” is reached. By pressing
“Scroll” twice “OP Hi” will be reached. This can be adjusted to be slightly above the
output limit which was being used in manual mode to achieve the required evapora-
tion. This will prevent the PID controller from attempting to raise the filament current
above this level in the event of a fault condition.
EBE-1 17
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