EZT-550 Controller Manual
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5.1.1 How to Adjust Tuning Parameters
Should you have an application where the standard factory parameters do not provide acceptable control, the
following guidelines will assist you in adjusting the PID settings for improved control.
Note: When making changes to the PID parameters, it is necessary to give the system enough time for the
new settings to take affect. It can take up to 15 minutes to see the results of an adjustment. Also,
tuning the system to operate at one specific point may cause erratic control at other points. Choose
your settings wisely.
Temperature
1) Set up your test load and turn any live loads on.
2) Set the setpoint for ambient, 24C (75F). This is the most difficult temperature control point due to the
fact that very little heating or cooling is needed to maintain it.
3) Set the reset and rate values for heating and cooling to zero.
4) Starting with PB bands of 1.00, increase the PB bands for heating and cooling until the oscillation
around setpoint stabilizes, i.e., little to no overshoot beyond setpoint. (approximately 0.3C (0.5F) max)
5) Add reset to both heating and cooling starting at a value of 8.00. Reduce the values until oscillation
begins, and then increase them slightly to reduce the oscillation. Some cases may require the values to
be increased from the initial 8. Typical values are between 5.00 and 10.00.
6) A typical setting for the rate will be approximately 0.4% of the reset value.
7) Verify operation of the chamber at the desired points. Some minimal adjustments may be needed for
specific points.
Humidity
1) Set up your test load and turn any live loads on.
2) Set the setpoint for ambient, 24C (75F), and the humidity for 50%. This is the most difficult humidity
control point due to the fact that very little moisture is needed to maintain it.
3) Set the reset and rate values for humidification and dehumidification to zero.
4) Starting with PB bands of 20.00, increase the PB bands until the oscillation around setpoint stabilizes,
i.e., little to no overshoot beyond setpoint. (approximately 1% max)
5) Add reset starting at a value of 8.00. Reduce the values until oscillation begins, and then increase them
slightly to reduce the oscillation. Some cases may require the values to be increased from the initial 8.
Typical values are between 6.00 and 10.00.
6) A typical setting for the rate will be approximately 2.5% of the reset value.
7) Verify operation of the chamber at the desired points. Some minimal adjustments may be needed for
specific points.
Note: Typically, larger PB bands require larger rate values to make the system respond to temperature
changes faster in order to maintain setpoint at extreme conditions. Most overshoot conditions can
be adjusted by altering the reset value. The proportional band determined at ambient is generally
acceptable throughout the entire chamber control range.
