Bacharach 3015-4286 - Manual (Page 20)

Single Zone Gas Monitor
16 P/N: 3015-4256 Rev 13
Jumper the ‘Live/Positive’ line of an external power source (DC devices) or the monitor’s AC input (AC
devices) to the ‘Common’ terminal on the relay connector.
Connect the ‘Live/Positive’ end of the strobe or horn to the ‘NO’ terminal of whichever level of alarm is
appropriate for the application.
For protection, install an in-line fuse of the appropriate size and design for the external alarm device being
used.
The other end of the strobe or horn is connected to the ‘Neutral/Negative’ leg of the external power
source (DC devices) or monitor’s AC input (AC devices).
2.8. 4–20 mA Current Loop Interface
An external 4–20 mA monitoring device (e.g., chart recorder) can be connected to the SZ monitor using a
shielded-twisted-pair cable. Use any of the service knockouts to gain access to the interior of the monitor.
Locate the 4
−20 mA Connector (page 11), remove it from the circuit board, and then remove the resistor
or shorting wire from its terminals.
IMPORTANT! The monitoring device must be isolated from ground (floating).
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 may cause a loop fault
code <0010> to occur (page 23).
Secure the wire leads from the external monitoring device to the 4–20 mA connector as shown in the
diagram below, making sure that the polarity at this connector matches the wiring at the monitoring
device.
The default current-to-ppm factor is set to 0.016 mA = 1 ppm, providing a measurement range 0 ppm
(4 mA) to 1,000 ppm (20 mA). Note that the current-to-ppm factor can be changed using the monitor’s
LOOP function (page 22).
To facilitate loop zero and span checking, note that when the LOOP function is selected the loop output is
set to 20 mA, and upon exiting this function the loop output is set to 4 mA.
Figure 2-11. 4–20 mA Current Loop Connector
CAUTION: Never apply power to the 4–20 mA Current Loop Connector from an external
power supply. Connect only a load resistor and/or a floating measurement device.