Rohde & Schwarz HMC8012, Руководство пользователя

Страница: 47 / 69

47
Instrument Functions
measurement per second, for MEDIUM it is 10 measure-
ments per second and for FAST it is 100 measurements per
second.
5.4 Measuring Resistance
For the resistance measurement, connect measurement
cables with clamps to the respective connectors on the
front panel of the instrument. A two-wire measurement
only requires the COM and V connectors. A four-wire
measurement also requires the LO/HI connectors (SENSE).
After connecting the cables and connecting with a resis-
tance, press the Ω key. The resistance value will show on
the display. During a resistance measurement, the cable
resistance (cable offset) requires particular attention.
Especially for small resistances which may be close to
the cable offset it is recommended to zero the measure-
ment section. A zero measurement is also called a relative
measurement, i.e. each measurement value indicates the
difference between a saved zero value and the input signal.
In this case it is necessary to short circuit the measurement
cables and then press the NULL key. This triggers the offset
correction of the entire measurement section. This value
will be shown on the display below the main measurement
value. The line resistance of the measurement cable, con-
tact resistances and thermoelectric voltages between diffe-
rent metals have been intentionally eliminated by this offset
correction. The compensation values will not be stored
after the ¸HMC8012 has been switched off and have to
Fig. 5.6: Measuring resistance (2-wire)
- +
resistance 2-wire
(Ω)
be redetermined. In addition, you may also enter the NULL
value numerically or via knob.
On page 2|2 of the Ω main menu, you can use the soft
menu key MODE to distinguish between 2-wire operation
(2w) and 4-wire operation (4w - connect SENSE cables).
The soft menu key ADC RATE and the knob allow you to
set the display refresh rate for the 2-wire operation (2w)
to SLOW (5 measurements per second), MEDIUM (10
measurements per second) or FAST (50 measurements per
second). For the 4-wire operation (4w), you can set the dis-
play refresh rate to SLOW (5 measurements per second),
MEDIUM (10 measurements per second) or FAST (25 mea-
surements per second).
5.5 Measuring a Capacity
To measure a capacity, you can connect a capacitor with
the ¸HMC8012 multimeter via silicon measurement
cables and clamp-type test probes, for instance. Use the
COM and V connectors on the bottom. Once the CAP key
on the front panel of the instrument is used, the capacity
value will be shown on the multimeter display.
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
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 maximum accuracy in measurements is achieved when using
the setting SLOW (ADC Rate).
Fig. 5.8: Measuring the capacity
- +
capacity
Fig. 5.7: Measuring resistance (4-wire)
- +
resistance 4-wire
(Ω)