G.R.A.S. Sound & Vibration
Power Module Type 12AR - Page 6
3.
Batteries and External Power
The Power Supply Type 12AR can be powered either by internal batteries or from an external
power supply. If an external DC power supply is connected via the
Ext. Supply
socket on the
rear panel; any batteries inside the unit will automatically be disconnected.
The external power supply should be a mains/line adapter regulated to supply 4.5 - 24 V DC
with the centre pin as the + terminal. When the Type 12AR is switched on via the
l
–
O
switch
on the front panel, the green
Power
LED will light up, and the red
Low Batt.
indicator should
remain extinguished to ensure correct operation of the unit. If the
Low Batt.
LED lights up,
either the external power supply voltage is too low, or the batteries need changing. To ensure
valid measurements, we recommend that you change batteries whenever the
Low Batt.
LED is
lit; there will be at least one hour’s use left after it fi rst warns of low batteries.
To change the batteries, squeeze and pull out the battery drawer from the battery compart-
ment on the rear panel (see Fig. 3.1). Remove all 4 batteries and replace them with fresh ones,
Fig. 2.3 Rear panel of Power Supply Type 12AR
Fig. 3.1 Battery drawer open: note polarity of batteries
Latched switch
for selecting
polarization
voltage:
0 V or 200 V
Input for external
power supply
4.5 - 24 V DC
Fuse 160 mA
low-impedance,
slow-blow
Battery drawer
for 4 alkaline
batteries LR
6/AA
