MERIDIAN
UNIVERSAL GAS DETECTOR
INSTALLATION
4-30
USE AND DISCLOSURE OF DATA
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4.1.19 Connecting a Device to a Power Supply: 2-wire
To install a 2-wire connection from the VDC power supply and a 4-20mA receiver (or other devices capable of
measuring 4-20mA inputs) to the device, follow the steps below.
1. A 2-wire connection (without any options) requires an operating voltage of 18-30 VDC from the power supply.
2. Route wires of appropriate size from source through conduit runs into the device housing (see Field Wiring in
Appendix A.1. Device Specifications
).
3. Connect ground wire the grounding/earth screw on the device’s housing.
4. 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.
5. Connect positive (+) and negative (-) leads from VDC power supply wires to TB1 on the 2-wire power supply
PCB. Specifically, the positive (+) connects to Pin1 (+V) and negative (-) connects to Pin2 (GND) on TB1
(refer to
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.
NOTE: The VDC power supply requirements are different when using the 2-wire PCB (see
).