Vescent Photonics D2-105, Руководство пользователя

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Vescent Photonics D2 Series Product Manual
running the tuning procedure while the laser is on. For each stage, follow the steps below to tune the
plants according to the Ziegler-Nichols tuning method:
1) Connect thermal load to Laser Controller.
2) Place Loop in proportional-only mode: Switch labeled “Proportional” is on, switch labeled “Diff
On” is off.
3) Turn the gain all the way down (trimpot labeled “PROPGAIN” all the way CCW).
4) Turn on temperature loop.
5) Adjust set-point to approximately desired temperature.
6) Turn up the gain. Keep increasing the gain until the temperature error (front panel BNC) just start
to oscillate or ring with very little damping. If oscillation too large, reduce gain. Measure the
period of oscillation.
7) Turn off the Laser Controller. Measure resistance between “GAIN” testpoint and “GND”
testpoint. Turn down the “PROPGRAIN” until this resistance reads 1.7 time less than its original
value (i.e. from 500Ω to 295Ω).
8) Take the measured oscillation period in step 6 and divide by two. Set the Integrator time constant
to this value. If you measured a period of oscillation of 14 seconds, turn on the 4
th
(2.2s) and 5
th
(4.7s) switches in the integrator bank, to get a time constant of 6.9s.
9) Turn off the “proportional” switch.
10) Turn the “DiffGain” trimpot all the way CW.
11) Set the “Differential” switches to the same position as the “integral” one. This works out to
setting a D time-constant roughly equal to 1/8 of the period of oscillation. For the previous
example, set the 4
th
(0.47s) and 5
th
(1.0s) switches on to get a time constant of 1.5s.
12) Turn on the “Diff On” switch.
13) Your thermal loop is now tuned. Power and Laser Controller wait for temperature to stabilize.
Change the setpoint and observe the temperature error and verify that the oscillations of damped
and the temperature stabilizes. You may be able to get better performance by tweaking the poles
and gain.
NOTE: Depending on the thermal design, nested temperature loops can fight each other, causing
oscillations and instability. If you observe this, you will need to reduce the gain and/or increase the time-
constants on the slower stage.
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