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Model 187 & 189
Users Manual
3-2
When measuring voltage, the meter acts like a 10 MΩ
(10,000,000 Ω) impedance in parallel with the circuit. This
loading effect can cause measurement errors in high-
impedance circuits. In most cases, the error is negligible
(0.1% or less) if the circuit impedance is 10 kΩ (10,000 Ω)
or less.
Measuring AC Voltage
The meter presents ac voltage values as rms (root mean
square) readings. The rms value is the equivalent dc
voltage that would produce the same amount of heat in a
resistance as the measured voltage. Your meter features
true rms readings, which are accurate for sinewaves and
other wave forms (with no dc offset) such as square
waves, triangle waves, and staircase waves. For ac with
dc offset, use
$.
Set up the meter to measure ac volts as shown in
Figure 3-1.
All pushbutton features are available in this function. The
blue button ( %) accesses decibel dBm or dBV)
measurements, discussed next in this chapter.
MIN MAXHOLD
REL
%
ms
Hz
RANGE
dB
dB
ac+dc
ac+dc
ac+dc
ac+dc
F
nS
mA
mA
A
mV
V
mV
V
OFF
C
A
A
A
A
mA
COM
V
TEMPERATURE
A
MIN MAXHOLD
REL
%
ms
Hz
RANGE
dB
dB
ac+dc
ac+dc
ac+dc
ac+dc
F
nS
mA
mA
A
mV
V
mV
V
OFF
C
A
A
A
A
mA
COM
V
TEMPERATURE
A
AutoHOLD
LOGGING
SAVECANCEL
FAST MN MX
SETUP
YES
NO
1000V
400mA
FUSED
10A MAX
FUSED
CAT
LOGGING MULTIMETER
189
CLEAR MEM
VIEW
Switch
Box
dB
V
dB
V
ach001f.eps
Figure 3-1. AC Voltage Measurement