5
3.5 Reading the mV scale
When reading the millivolt scale, remember that a
probe setting of 100mV equals 1 Amp (20Amp scale on
the Snap-on Low Amp Current Probe). Similarly:
A reading of: 0.8mV = 8mA
A reading of: 1.8mV= 18mA
A reading of: 21.8mV = 218mA
A reading of: 100mV = 1000mA or 1A
3.6 Current Measurement Applications
3.6.1 Parasitic Draw Measurement
Recommended Probe Setting: 20A scale
Note: Before taking measurements or clamping the
probe jaws around any wire, complete the Setup
steps below.
Setup
1. Use the On/Off and Range Selector switch to select
the 20A setting.
2. Perform the Low Amp Current Probe Zero
Adjustment procedure (refer to section 3.3).
Test
To measure parasitic draw:
1. Clamp the Low Amp Current Probe jaws around the
B+ supply wire to the power distribution box, or to
the positive or negative battery cable.
The parasitic draw readings display.
2. If a negative reading displays, open the probe jaws
and clamp the probe in the opposite direction.
Note: Computer-controlled vehicles require a small
amount of current to keep module memories alive.
Refer to the appropriate vehicle service manual for
module time-out and maximum parasitic draw
information. The term “time-out” refers to the amount of
time that modules operate, before going into sleep
mode.
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