Pulse Width Measurements; Maintenance; General Maintenance - Fluke 87 TRUE RMS MULTIMETER User Manual

Dwell (degrees) x No. of Cylinders x 100
% Duty Cycle =
To make a dwell measurement, set the rotary switch to F,
select the 40V range, press Ftwice (the %
annunciator on the right side of the LCD should turn on),
and press the T(to select the negative trigger slope
so the measurement will be the "off" or points closed
time). Then connect the COM input to ground, and
connect the VJL input to the low (or switched) side of
the coil. Most automobiles have the points closed for a
duty cycle between 50-70%.

Pulse Width Measurements

For a periodic waveform (that is, repetitive at equal time
intervals), a duty cycle measurement can be easily
converted to pulse width. First measure the frequency and
then measure the duty cycle. Toggle T to select the
polarity of the pulse you want to measure. To convert
frequency and duty cycle measurements into a pulse
width, use the following:
% Duty Cycle / 100
Pulse Width =
Frequency
360 degrees

Maintenance

Repairs or servicing not covered in this manual should
only be performed by qualified personnel as described in
the 80 Series Service Manual (refer to Table 7 for part
number).

General Maintenance

Periodically wipe the case with a damp cloth and
detergent (do not use abrasives or solvents). If the input
alert is falsely activated by moisture:
1. Turn the multimeter off and remove all test leads.
2. Shake out the input receptacles.
3. Use a clean swab in each of the four terminals to
dislodge and clean out the contamination.
4. Soak a new swab with the cleaning and oiling agent
WD40. Work this swab around in the A and mA A
terminals. Since the oiling agent insulates the
terminals from moisture-related shorting, this
preventive treatment ensures against future
erroneous Input Alerts.
Maintenance
29