Amprobe ACD-14 PLUS Mode D'emploi page 10

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Measuring μA Current - See Figure 9
1. Set the Function Switch to and press the SELECT button for AC or DC is displayed.
2. Connect the test leads: Red to +, Black to COM.
3. Turn OFF power to the circuit being measured and break the circuit for connecting
test leads.
4. Turn ON the circuit and read the display.
μA Current function
Application notes:
The DCμA 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 :
1-1) For gas or oil flames (Minipeeper):
• Low supply voltage
• Detector location
• Defective detector wiring
• Dirty viewing windows
• Faulty Minipeeper
1-2) For oil flames (Photocell):
• Detector location & wiring
• Smoky flame or poorly adjusted air shutter
• Faulty Photocell
• Temperature over 165 °F (74 °C) at photocell
1-3) 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
flamerod
• Temperature in excess of 600 °F (316 °C) at the flame electrode insulator causing
short to ground.
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