Amprobe ACD-14-FX Clamp-On-Multimeter - Manual (Page 13)

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Application notes:
The DC µA 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, 1.5µA for an ultraviolet type, or 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°F (74°C) at photocell
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°F (316°C) at the flame electrode insulator,
causing short to ground.
HOLD
The hold feature freezes the upper ACA display for later viewing. Press the HOLD button
momentarily to activate or exit this feature.
MAX
The Max feature compares and displays the measured maximum value (on the upper ACA
display) as fast as 25ms with auto-ranging capability. Press the MAX button for 1 second
or more to activate or exit this feature.