Application Note: Flame Current Measurement - Suburban SW10P Service Training Manual

aPPlicatiOn nOte
FLAME CURRENT MEASUREMENT
LOCAL FLAME SENSING (Single Spark and Sense)
With power off, connect a DC micro ammeter (D'Arsonval movement type) as shown in the diagram below. (The meter
should be protected from high voltage surges which could damage the meter movement. A 1.5µF 200 volt film capacitor
across the meter terminals or lead wires will provide adequate protection). The lead wires and terminals must be isolated
from other surfaces to prevent the H.V. signal from arcing to ground during the trial-for-ignition period.
Apply power. Once the flame is established and the sparks shut off, a flame sense current of 1.5µA DC minimum is required
for proper operation.
CAUTION: Due to possible conditions, do not touch the micro ammeter or lead wires during the flame sense test. Always
remove power before any adjustments.
1.5µF
A
HV
0 to 50µA
METER
GND
REMOTE FLAME SENSING (Single Spark and Sense)
With power off, remove the sense wire from the electrode terminal and install a DC micro ammeter in series with electrode
terminal and sense wire, as shown in the diagram below.
Apply power. Once flame is established, a flame sense current of 1.5µA DC minimum is required for proper operation.
When Remote Flame Sensing is used, it is not necessary to employ the 1.5µF protection capacitor across the meter.
However, since it does not affect the performance of the micro ammeter, it may remain in place at all times.
A
0 to 50µA
METER
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