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2. When using Capacitance function, discharge capacitor(s) before making any
measurements. Large value capacitors should be discharged through an appropriate
resistance load
DCµ µ µ µ A Current function (Models 079 & 076 only)
Inputs are made through the test lead terminals COM/+.
Application notes:
The DCµ µ µ µ A function is designed especially for HVAC/R flame sensor applications. The
0.1µA resolution is useful for identifying the minute current changes in flame detector
applications. Flame signal current check should indicate steady flame signal of at least
2µA for a rectification type, or 1.5µA for an ultraviolet type (8µA for self checking
systems). If a flame signal current with inadequate strength or fluctuation beyond 10%,
check the following to avoid the risk of unwanted flame relay dropout :
For gas or oil flames (Minipeeper):
Low supply voltage
Detector location
Defective detector wiring
Dirty viewing windows
Faulty Minipeeper
For oil flames (Photocell):
Detector location & wiring
Smoky flame or poorly adjusted air shutter
Faulty Photocell
Temperature over 165
For gas flames (Flame Rod):
Ignition interference (A flame signal current difference with the ignition both on and
off greater than 0.5µA indicates the presence of ignition interference)
Insufficient ground (must be at least 4 times the detector area)
Flame lifting off burner head (ground), or not continuously in contact with the flame
rod
Temperature in excess of 600
short to ground.
o
o
F (74
C) at photocell
o
F (316
o
C) at the flame electrode insulator causing
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