Thermo Scientific Thermo Scientific 3906, Operating Manual

Page: 51 / 104

Thermo Scientific Model 3900 Series | 8-5
Handling and Control |
Chapter 8
The humidity alarm is a function of the humidity controller (Figure 8-6). When the cabinet
humidity goes outside the set parameters of the controller, the #4 indicator on the
controller lights, the audible alarm sounds and the humidity alarm indicator on the control
panel lights. The alarm can be silenced by pressing either EZ key.
Set the Operating Temperature
The Watlow temperature controller’s upper numerical display shows the actual
temperature inside the environmental chamber. The lower display shows the temperature
setpoint.
To change the setpoint, press the Up or Down Arrows. Temperature is set in one °C/°F
increments.
Set the Operating Humidity
The Watlow humidity controller’s upper numerical display shows the actual humidity
inside the environmental chamber. The lower display shows the humidity setpoint.
Figure 8-7
Changing Humidity
To change the setpoint, press the Up or Down Arrows. Humidity is set in one percent
increments.
NOTE
The humidity controller’s high and low limits are factory-set at 100% and 0%.
Therefore, the system will go into the alarm state when the humidity exceeds
these percentages by one percent. When operating the environmental chamber
near these high or low humidity levels, frequent alarms may occur. This will
require that the controller’s high or low limit be reset to three or four percent
over the high limit or three or four percent under the low limit. Refer to the
Watlow User’s guide provided. Refer also to “Configuration Record” on
page 13-8.
Actual humidity
in chamber
Humidity
setpoint
Raise or lower
setpoint