5
Battery
Operation
(M68D1)
Model M68D1 has a battery compartment for four
“AA” size batteries (type LR 6). It is opened by un-
screwing four plastic knobs and removing the cover.
The right polarity is shown on the battery holder. To
ensure long battery life it is recommended to use alka-
line batteries. Accumulators may be used as well. You
can operate the instrument on NiMH or NiCd. How-
ever, by reason of the lower voltage of accumulators,
the battery control will not work.
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Please take discharged batteries out of the instrument to
avoid damage by leakage. Also, remove the batteries if
the unit is not in use for a longer period.
Voltage
Control
All models of M68 series have an LED “BAT O.K.”
indicating sufficient supply voltage. It lights up green,
as long as the voltage is above 5 V. It works for battery
operation as well as for external power supply.
Fault
Protection
The instruments are protected against false polarization
and short-time excess voltage up to 60 V.
Grounding
Conception
The inputs and outputs of the signal conditioners are
single ended, i.e. asymmetrical. In case an additional
signal ground connection is required, ground is avail-
able via a separate connector at the rear of the instru-
ments. For the Models M68D1 and M68D3 this con-
nector is a 4 mm banana jack. The signal ground of
Model M68R1 can be found at the 4-pole frame con-
nector. The case of the instruments is internally con-
nected to ground.
The power supply is separated from signal ground. In
some cases it may be of advantage to connect the minus
pole of the power supply to signal ground, to avoid
ground loops. For this purpose you can plug in the
4 mm jumper (delivered with the instruments) at the
rear of Models M68D1 and M68D3. At Model M68R1
the terminals of the power supply socket can be con-
nected by a wire.
