American Magnetics 110 Liquid Helium Level Meter (CE-Marked) - Manual (Page 27)

17
Appendix
A.1 4-20 ma Current Loop Option
The 4-20 mA output utilizes pins 2 and 3 of connector J1. If the 4-20 mA
option is present, the voltage output is not available from pins 4 and 5. The
figure below shows the wiring diagram and the voltage requirements for
the power supply and receiver.
Caution
It is extremely important to observe all polarities and to not exceed
+36 VDC for the loop power supply in order to prevent damage to the
4-20 mA driver circuit.
Note
For maximum immunity to external electrical and electromagnetic
disturbances, all external cabling (except for the AC input) should be
shielded. The cable shield should be connected to the chassis of the
instrument by connecting to the J1 D-sub connector shell.
Note
For the 4-20 mA output to work properly, at least 12 V must be
present between J1 pin 2 and J1 pin 3, i.e. the voltage drop of the
receiver must be considered.
AMI
Level
Instrument
J1 pin 2 (+)
J1 pin 3 (-)
I
LOOP
+
-
+
-
R
L
Receiver
Loop
Power
Supply
+12 to +36 VDC