Hz S How To Use Dc-Coupled Hz To Check Bp/Map Sensors - Fluke 78 User Manual

78
Users Manual
Hz s How to Use DC-Coupled HZ to Check
BP/MAP Sensors
Use the dc-coupled Hz function for "pulsed-dc" tests on
parts like a mass air-flow (MAF) sensor, a manifold abso-
lute pressure (MAP) sensor, or a Hall sensor.
The following procedure demonstrates how to measure
dc-coupled frequency to test a barometric pres-
sure/manifold absolute pressure (BP/MAP) sensor:
1. Insert the test leads into the jacks (Figure 11).
Turn the rotary switch to Hz s.
2.
Press R for 2 seconds to toggle between the
3.
volts dc and frequency function.
"DC" and "Hz" show on the display when dc-coupled
frequency is selected.
4. Connect the test leads to the jumper wires.
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5. With the ignition KEY ON but the ENGINE OFF,
pump the vacuum up with a hand vacuum pump.
Watch the frequency change on the display. Compare
the frequency at various vacuum readings with the
specifications in your car's service manual. At 0
inches-of-Hg, frequency should match the specifica-
tion for your altitude.
When measuring frequency in VDC, the meter
displays frequency on the digital display. The bar
graph is turned off and the meter ranging is
manual only.
Note