7 | 18
4.1 Supply voltage
The supply voltage of version -24E is in the range of 18 to 30 VDC and version –E12 within 10 to 18
VDC. The presence of the supply / internal operating voltage is indicated by the 2 green LEDs on the
front.
To protect the electronics (to the supply voltage version corresponding) an internal self-healing
“polyswitch-resettable®” fuse is built in. Whether an external additional fuse is necessary has to be
considered. However, an additional external delay fuse of 0,315 A is recommended.
If the indicator LEDs go off, the supply voltage and possibly existing external protection has to be
checked.
Notice:
During switch-on phase the amplifier is capacitive. Thus, the switch-on current is greater than
the operating current. This must be taken into consideration when dimensioning and selecting the
power pack, especially if several amplifiers are being wired to the same power source.
4.1.1 Galvanic isolation
The supply voltage of the amplifier is galvanically isolated from analogue output, sensor supply and
sensor signal. To unset this isolation, clamp 3 and 4 have to be bridged.
4.2 Strain gauge excitation voltage
The described measuring amplifier is able to supply one strain gauge transducer. Any strain gauge full
bridge with a bridge resistance of 300 Ohms or more may be connected. The transducer can be
supplied with a bipolar voltage of either ± 5 V (= 10 V) or ± 2,5 V (= 5 V). This value can be selected by
internal solder points and with 2 potentiometers for fine adjustment.
LP81-1
LP81-2
SG-Excitation
SET
SET
±5 VDC (=10VDC)
NOT SET
NOT SET
±2,5 VDC (=5 VDC)
