Noisy Resistance Measurements; Measuring Capacitance - Fluke 87 TRUE RMS MULTIMETER User Manual

87
Users Manual
In the conductance range, there is normally a
small residual reading with open test leads. To
ensure accurate measurements, connect clean
test leads to the meter and (with the leads open)
read the residual leakage in nanosiemens.
Correct subsequent measurements by using the
Relative mode (REL) to zero the display, which
subtracts the residual from the readings.
Diode leakage tests require that the diode junction be
reverse-biased when being measured. To do this, connect
the anode of the diode to the COM input terminal and the
cathode (ring) of the diode to the VJL input terminal.
Leakage at the test voltage being applied can then be
read in terms of conductance.
High-voltage, stacked diode, assemblies can usually be
tested for forward and reverse resistance changes using
conductance. These assemblies typically have such high
forward voltage drops that the diode test or resistance
modes cannot test them.

Noisy Resistance Measurements

Your Fluke meter is designed to tolerate up to several
volts of ac noise. Noise appears as changing numbers on
the digital display and as an oscillating analog display.
22
Note Changing the range may reduce the noise. To smooth out
the effect of noise on your readings, enter the MIN MAX
Recording mode and scroll to the average reading.

Measuring Capacitance

Caution
Turn off power and discharge the capacitor
before attempting a capacitance
measurement. Use the (F) function to confirm
that the capacitor is discharged.
The meter measures capacitance by charging the
capacitor with a known current, measuring the resultant
voltage, and calculating the capacitance. The
measurement takes about 1 second per range (push
button responses also take about 1 second). The
capacitor charge can be up to 1.2V.
K
For measuring capacitor values up to 5.0 F, turn the
rotary switch to MJ
, press the BLUE button, and
connect the test leads to the capacitor. The meter will
select the proper range automatically. Each measurement
takes about 1 second per range. When making repeated
measurements of similar values, press Kto manually
select the proper range and to speed up subsequent
measurements. For capacitors less than 5 nF or in noisy