Amprobe BDM40-UA Bench-Digital-Multimeter - Manual (Page 12)

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The light grey area around the ACV / DCV switch is extended up and to the right to enclose the five range values of
the voltage function. Push the range switch immediately above the value to be measured. The range selection
switches are interlocked in the same manner as the function switches.
Perform the following procedure:
1. If the test leads are not connected, plug them into your DMM: red test lead to the V- Ω terminal and
black to the COMMON terminal.
2. Select the 0.2V range.
3. Push the function switch to the DCV position.
4. With the POWER switch set to the OFF position, connect your DMM to a line power outlet rated at the
operating voltage and frequency of your instrument. Keep the probe tips apart, and not connected to a
circuit.
5. Push the POWER switch to the ON position. The LED should count down rapidly to a reading of
< ± .0020.
6. Select the ACV and 1000V range.
WX WARNING
LOCAL LINE VOLTAGE IS MEASURED IN THE FOLLOWING STEP. BE CAREFUL NOT TO
TOUCH THE PROBE TIPS WITH YOUR FINGERS OR TO ALLOW THE PROBE TIPS TO
TOUCH EACH OTHER.
7. Insert the probe tips of the test leads into the slots of a power outlet. The LED should display the true
local line voltage.
8. Push the DCV push-button switch. The LED should display near zero volts but there may be some
residual dc voltage on the power line due to non-linear loads such as SCR light dimmers.
9. Remove the test leads from the line power outlet.
Converting voltage measurements
Your instrument is one of a family of DMMs that actually measure the true rms value of an AC or AC + DC signal.
This is a feature that allows accurate measurement of common waveforms like distorted or mixed frequency sine
waves, square waves, sawtooth waves, noise, pulse trains (with a duty cycle of at least 10%), etc. In the past, the
methods used for AC measurement have introduced large errors in readings. Unfortunately, we've all grown used
to these erroneous voltage readings and depend upon them to indicate whether or not a piece of equipment is
working correctly. The data contained in Table 2 should help you convert between measurement methods.