45
Instrument Functions
5 Instrument
Functions
5.1 Measuring a DC / AC Voltage
A basic measurement that can be performed with a mul-
timeter is the measurement of a DC or an AC voltage. To
measure a DC or AC voltage, you can connect a voltage
source to the ¸HMC8012 multimeter via silicon test
leads, for instance. Use the COM and V connectors on the
bottom right. Once the DC V / AC V key on the front panel
of the instrument is used, the DC or AC voltage value will
be shown on the multimeter display.
In addition, it is possible to show a second function (2nd)
on the display. The soft menu key 2nd FUNCTION and
the knob allow you to select AC V, DC I, dB or dBm. The
selected function is shown above the main measurement
value display. The menu display changes depending on the
selected second function. The soft menu key REMOVE 2nd
allows you to hide the second function from the display.
You can select the option SLOW, MEDIUM or FAST via soft
menu key AC FILTER and knob. A lower setting (SLOW) en-
sures more stable measurement values. However, the mea-
surement is slow and signal elements of higher frequency
will be attenuated. Depending on the input frequency, this
function will smoothen the displayed value. The setting
MEDIUM is saved as default value. Select the setting
SLOW for an input frequency of
<
50 kHz, and select FAST
for a setting of
>
1 kHz.
To compensate for the line resistance of measurement
cables, it is necessary to short circuit the measurement
cables and press the NULL key. This triggers the offset
correction of the entire measurement section. This value
- +
voltage source
(AC/DC)
Fig. 5.1: Measuring a DC or AC voltage
Please note that for an AC measurement, RMS values will be
shown on the display.
The AC filter represents a display filter and not a low-pass filter. The
signal will be not circumcised. Fluctuating signals can be better
read.
will be shown next to the soft menu key NULL and on
the display below the main measurement value. The line
resistance of the measurement cable, contact resistan-
ces and thermoelectric voltages between different metals
have been intentionally eliminated by this offset correc-
tion. The compensation values will not be stored after the
¸HMC8012 has been switched off and have to be rede-
termined. In addition, you may also enter the NULL value
numerically or via knob.
The soft menu key ADC Rate and the knob allow you to
set the display refresh rate to SLOW (5 measurements per
second), MEDIUM (10 measurements per second) or FAST
(200 measurements per second).
The function AUTO ZERO on page 2|2 of the DC V main
menu may be activated (ON) or deactivated (OFF). If this
function is activated, the instrument automatically compen-
sates for the connected measurement cables and deducts
this offset from the measurement result (automatic zero
measurement).
The input impedance can be set via soft menu key INPUT
IMP. to 10 MOhm or >10 GOhm.
If the second function (2nd FUNCTION) is activated (dB or
dBm), you have the option to define a
reference value. For
the function dB, the reference value is the voltage (REF.
VALUE). You can set the reference value numerically or via
knob. If a
reference value is defined, you can reset the pre
-
viously selected reference value via soft menu key NULL.
For the function dBm, the reference value is 1mW and is
often used for RF signal measurements. If the dBm func-
tion is activated, the multimeter performs a measurement
and calculates the power supplied to a comparator resis-
tance. The reference value (REF. VALUE) in this case is 50,
75 or 600 Ω. In addition, you can set a user-defined value
(USER) either numerically or via knob.
The maximum accuracy in measurements is achieved when using
the setting Slow (ADC Rate).
If the ADR RATE = FAST is selected, the AUTO ZERO function is
deactivated automatically.
The impedance setting is dependent on the measurement range
Fig. 5.2: ACV menu with 2nd function
Summary of Contents for HMC8012
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