Appendix B. CNF4 Heater/Ventilator
B-10
'CNF4 heater control - the heater will be turned on when flag(2) is set high
SW12 (2,flag(2))
CallTable cnr4_data
CallTable cnr4_ts
NextScan
EndProg
B.5 CNF4 Heater/Ventilator Maintenance
B.5.1 Testing the Heater
The optional CNF4 consists of a heater and a ventilator. To check the heater unit,
measure the resistance between the two heater wires (green and yellow). The
resistance value of the heating resistor inside should be around 15
Ω
(cable
resistance should add about 0.026
Ω
per each foot of cable). An infinite
resistance reading indicates the likelihood of a broken wire, or cable.
B.5.2 Testing the Ventilator
To check the ventilator, first measure the impedance of the ventilator motor. The
value should be around 30
Ω
(cable resistance should add about 0.026
Ω
per each
foot of cable). If the correct resistance value is measured, but the ventilator still
mal-functions, it is possible that the ventilator is stalled by an object blocking the
fan. Remove the black cover at the bottom side of the ventilator unit, by prying it
open with a small flat-head screw driver or by pulling it straight out. Inspect the
fan inside for any object that might impede the fan’s rotation. Upon completing
the inspection, put the filter and the cover back in place.
B.5.3 Replacing the Filter for the Ventilator
The filter needs to be checked for every 6 to 12 months. Remove the black cover
at the bottom side of the ventilator by prying it open with a small flat-head screw
driver or by pulling it straight out. Inspect the filter for dust and particles that
might impede the air flow into the ventilator. The filter can be cleaned with warm
clean water, or can be replaced with the new one. You can purchase the
replacement filters from Campbell Scientific (P/N #26010, a set of 5).
