Wavelength Electronics LFI-3751, User Manual

Page: 59 / 132

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2. Adjusting the I Term
•
Rotate the Display Select Switch to I (Shift Button ON) .
•
Rotate the Digi-Pot Adjust Knob to change the displayed value.
•
RS-232 Command: [I]
•
Increasing the integrator time constant will improve the instrument’s
control loop stability (especially with large thermal loads). Increasing
the integrator too much produces a sluggish response and long settling
times. If you notice the temperature of your load
slowly approaching the
setpoint temperature, then reduce the integrator time constant. Reducing
the integrator too much can cause thermal cycling.
P ACT T
LIM I
AUX T
TE V
SET T
TE I
B
C
I
A
D
Display Integral
Time Constant
OFF
ON
Integral Time Constant Range
0.0
0.4 to 10 seconds
3. Adjusting the D Term
•
Rotate the Display Select Switch to D (Shift Button ON) .
•
Rotate the Digi-Pot Adjust Knob to change the displayed value.
•
RS-232 Command: [D]
•
Increasing the differentiator time constant also improves the instrument’s
control loop stability. The differentiator term is typically only useful or
necessary for large, hard to control thermal loads. The differentiator
term can amplify electrical noise from the sensor. If you notice the
temperature of your load
quickly cycling then reduce the differentiator
time constant.
P ACT T
LIM I
AUX T
TE V
SET T
TE I
B
C
I
A
D
Display Differentiator
Time Constant
OFF
ON
Differentiator Time Constant Range
0.0
1 to 100 seconds
Chapter 2 - Front Panel Operation
Setting the P, I, and D Constants
2