PRESYS
Instruments
T-650PH
Page 19
6 - PID Control Parameters
The T-650PH temperature calibrator has a PID control algorithm to calculate the
block control output.
The dry block stability and response time features are related to the PID
parameters, explained below:
The
K
parameter (proportional gain) amplifies the error signal between the
setpoint and the block temperature to establish the output signal. When this parameter
is very high, the output reaction is very quickly, however this can take the system into
oscillation. Decreasing this parameter, the dry block would not be able to react quickly
enough to external variations, giving the impression of a sudden out of control.
The
I
parameter (integral gain) is responsible for the integral action and it is the
most important part in the setpoint control. While an error persists between the setpoint
and the block temperature, the integral action will actuate on the output signal until the
error is brought to zero.
The
D
parameter (derivative gain) is responsible for the derivative action that
provides a quick response at the control output resulting from any rapt variation in the
block temperature. It is used to eliminate oscillations. However, it can cause oscillations
in the presence of much noise.
All temperature calibrators are tuned in factory and the parameters are close to
the optimum ones. In case one wants to improve a specific feature of the calibrator
(stabilization time or response time, for instance), make sure the alteration is made
reasonably.
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