Thermo Scientific 3911, Operating Manual

Page: 63 / 76

Forma Model 3900 Series | 13-7
Service |
Chapter 13
Watlow PM Control Auto Tune
Prior to performing an RH controller auto tune, heat output 2 in the RH controller
should be configured to have a minimum output of 10% due to heater lag in the RH
system. Additionally, the cabinet should be running a minimum of 24 hours at the
desired temperature control setpoint. This will help ensure the steam generator is at a
good operating temperature and the cabinet has reached equilibrium before the auto
tune is performed.
See procedure below for setting the minimum output low setting to 10% in the RH
controller.
Changing RH Control Output 2 Minimum Output to 10%
1. Remove software lockout.
2. Go into SET UP menu by holding the up and down arrow keys for 6seconds (lower
display reads “Set”, upper display “Ai”).
3. Go to OUTPUT menu by pressing the down arrow key until “OtPt” appears in the
upper display.
4. Press the ADVANCE key once (lower display reads “OtPt” and upper display “1”).
5. Press the up arrow key once (lower display reads “OtPt”, upper display “2”).
6. Press the ADVANCE key. The lower display reads “o.Lo”. Press the up arrow key until
the upper display reads “10”.
7. Press the INFINITY key several times until the control returns to normal display.
Auto Tune Procedure
The procedure for changing PID tuning values follows.
1. Remove software lockout, if not already performed.
2. From home screen, press and hold the up and down arrow keys until the display
reads “Oper” in the lower display and “Ai” in the upper display.
3. Press the down arrow key until “LOOP” appears in the upper display.
4. Press the ADVANCE key until “A.Tun” appears in the lower display.
5. Press the up arrow key until “YES” appears in the upper display.
6. Press the INFINITY key to return to home screen.
The lower display flashes “TUNE” until Auto Tune has successfully completed.
NOTE
RH control minimum output value should remain at 10% after performing Auto Tune. This
provides tighter RH control for most settings.