40
Subject to change without notice
STOP
STOP
C o n t r o l e l e m e n t s a n d d i s p l a y
Control elements and displays
Display
16 digit display for displaying measurement results, menu
selection and menu items.
POWER
Button for activating standby-function. The controls and the
display are turned off. The instrument itself stays turned on
as long as it is connected to the supply voltage. This has the
advantage that the instrument is immediately functional after
turn-on. Also the reference voltage source will remain
energized, so any drift after turn-on will be eliminated, also
its long term drift will be substantially improved.
To switch-off the instrument completely, the line switch on
the back panel has to be operated.
HOLD
“Freezing“ of the displayed measured value.
By pressing one of the function selection buttons
to
15
or
MENU
18
the HOLD function is left.
ZERO
Zero for DC voltage, DC current, 4-wire-resistance and 2-wire-
resistance measurements. The ZERO function is not provided
for AC voltage and AC current measurements. Both cables
have to be shorted and the ZERO button has to be pressed.
This results in elimination of the resistances of the measure-
ment cables, resistances and thermal voltages at the junction
of different metals.
Compensation values remain, even after turn-off the instru-
ment. They have to be redetermined if necessary.
The ZERO button is deactivated in the measuring
functions
ϑ
PT for PT sensors or
ϑ
TH for
thermocouples.
Zero adjustment with temperature measurement
1. With regard to the type of temperature sensor one the
following measurement ranges must be chosen:
PT100
Ω
2 wire /
Ω
4 wire
1 k
Ω
range
PT1000
Ω
2 wire /
Ω
4 wire
10 k
Ω
range
Thermocouple V
DC
100 mV range
Whether 2-wire- or 4-wire-measurement has to be
selected depends on the PT temperature sensor used.
2. Short the temperature sensor.
3. The ZERO button
is to be pressed to compensate for
influences within the measurement circuit.
4. After compensation jump to the adequate temperature
measurement function by pressing ZERO
Some measurement instruments offer an „auto-
matic zero function“. This function regularly inter-
rupts the measurement and shorts the input. Then
a partial 0-adjustment is made.
The HM8112-3 has no AUTO ZERO function,
because the zero adjustment of the complete
measurement circuit is very important.
LOCAL
By sending a command via interface to the HM8112-3 the
instrument is set to the remote mode. Remote control is
switched off by pressing button LOCAL. The instrument
returns to manual mode and can be operated from the front
panel.
Buttons for the various measurement functions
If the measurement function is changed, the HM8112-3
assumes the sampling rate selected, unless a sampling rate
between 10 s and 60 s is chosen. Then changing the measuring
function will set the sampling rate automatically to 1 s.
The buttons offering more functions are illuminated. Naturally,
other measuring functions can be called up by pressing
unlighted buttons. The terminals are illuminated, too, and
indicate the terminals to be used with the corresponding
functions.
Voltage Measurement
V
DC
Direct voltage measurement up to 600 V. No auto range
function in 100 mV and 1 V ranges.
1
2
27
3 4
5
6
7 8
9 10 11 12 13 14 15
16 17
19 20 18 21 22 23
24
25
26
V
A
SENSE
SOURCE
LO
HI
max.
250Vrms
max.
850
Vpk
max.
850
Vpk
Ω
,
ϑ
FUSE
1A
F250V
CAT
II
max. INPUT
600Vrms / 1Arms
+
–
Direct or
alternating voltage
