Forma Scientific 3546 - Adjusting the Span Pot

Forma Scientific, Inc._____________________________________________Service
6-6
Side View of the CO
2
Control Module
Figure 6-2
c. Adjusting the Span Pot (Refer to Figure 6-2)
 Turn ON the CO
2
at the supply.
 Turn the CO
2
setpoint to 10%. Allow the CO
2
to stabilize at 10% on the
readout and control (inject light will cycle) for a minimum of 15 minutes.
 Using a FYRITE or other measuring device, check the CO
2
level in the
chamber until two consecutive readings agree.
 Turn the CO
2
setpoint to 0.0% to prevent CO
2
from being injected into the
chamber during the adjustment.
 Adjust the span pot so the digital display agrees with the FYRITE reading.
 Turn the setpoint back to 10%, and allow the CO
2
to control and stabilize
for a minimum of 15 minutes.
 Check the CO
2
in the chamber with a FYRITE or similar device until two
consecutive readings agree. If the digital display is within plus or minus
1.0% of the FYRITE reading, proceed to the next step, "Recheck the Zero
Adjustment." If the reading is not within plus or minus 1.0%, repeat Steps 3
through 6 of this procedure.