Bacharach H25-IR - Manual (Page 25)

H25-IR Preparing for Operation
Instruction 3015-4342 19
2.8 4–20 mA Current Loop Connection
An external 4
20 mA monitoring device (e.g., chart recorder) can be connected to the H25-IR using a shielded-
twisted-pair cable.
IMPORTANT! The monitoring device must be isolated from ground (floating).
Locate the 4
20 mA connector on the rear of the unit (refer to Section 1.7.2 Rear View), and then remove the
resistor or shorting wire from its terminals.
NOTE: A 100 ohm, ¼ W resistor must be connected to the 4–20 mA connector if no external monitoring device
is used. Failure to install this resistor will cause a “Loop Open Error” to occur (refer to Section “4.3 Fault ”).
Secure the wire leads from the external monitoring device to the connector as shown in the diagram below,
making sure that the polarity at this connector matches the wiring at the monitoring device.
4–20 mA Current Loop Connector
CAUTION: Never apply power to the 4–20 mA Current Loop Connector from an
external power supply. In addition, connect only a load resistor or a floating
measurement device.
The default current-to-ppm factor is set to 0.016 mA = 1 ppm, providing a measurement range of 0 ppm (4 mA)
to 1,000 ppm (20 mA). Note that the current-to-ppm factor can be changed using the instrument’s LOOP
function (refer to Section 2.5.4 4–20 mA Loop).
TIP: The loop output can be checked per Section “5.1.5 Loop Test”.