MERIDIAN
UNIVERSAL GAS DETECTOR
INSTALLATION
4-32
USE AND DISCLOSURE OF DATA
Information contained herein is classified as EAR99 under the U.S. Export Administration Regulations. Export, reexport or diversion contrary to U.S. law is
prohibited.
4.1.20 Connecting a Device to a Power Supply & Receiver: 4-wire
To install the 4-wire connection (sourcing and sinking) from the VDC power supply and a 4-20mA receiver (or
other devices capable of measuring 4-20mA inputs) to the device with isolated loop power, follow the steps
below.
1. Route wires of appropriate size from source through conduit runs into the device housing (see Field Wiring in
Appendix A.1. Device Specifications
).
2. Connect ground wire to device’s grounding/earth screw on its housing.
3. Unscrew the setscrew and housing cover, then pull on the LCD PCB/CPU PCB set, removing it from the four (4)
standoffs, to gain access to the lower PCB Stack.
4. Connect positive (+) and negative (-) leads from 10 to 30VDC power supply wires to TB1 on the isolated 4-
20mA PCB. specifically, the positive (+) connects to Pin2 (+V) and negative (-) connects to Pin1 (GND) on
TB1.
5. Connect positive (+) and negative (-) leads from receivers) to TB2 on the terminal/relay/MODBUS RS-485
PCB (refer to
Connection for 4-Wire Sourcing with Isolated Loop Power Supply
Connection for 4-Wire Sinking with Isolated Loop Power Supply
WARNING:
ENSURE RECEIVERS AND POWER SUPPLIES ARE NOT POWERED WHEN
INSTALLING PCB INTO THE DEVICE. FAILURE TO DO SO COULD RESULT IN INJURY OR
DEATH.
WARNING:
ENSURE THE ATMOSPHERE IS FREE FROM COMBUSTIBLE AND/OR TOXIC
GASES PRIOR TO STARTING THIS PROCEDURE. FAILURE TO DO SO COULD RESULT IN INJURY
OR DEATH.
CAUTION:
RFI may be generated if wires are not appropriately shielded or share conduit with
other AC power conductors. Protect wires with appropriate shielding practices to prevent negative
equipment performance.
NOTE: To prevent grounding issues, ensure you have a good ground/earth wire attached to the
housing and back to the receiver’s ground.
NOTE: It is not necessary to remove the wire ribbon cable from the upper and lower PCB stacks.
