Relay Output, Contact Input; Mechanical Relay Option; Solid State Relay Option; Opto-Isolated Inputs/Outputs - Omega RD8800 User Manual

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Chapter 2 Installation and Wiring

2.3.4 Relay Output, Contact Input

WARNING

To prevent the possibility of electrical shock, use extreme caution when wiring

contact output connections. Hazardous potentials may exist on contact output

terminals which are floating with respect to instrument ground. These hazardous

potentials may be exposed on the rear terminal panel of your instrument. Any

voltage potentials at the contact circuit will exist on the instrument's respective

contact output terminals (i.e. line-powered circuits).

The Recorder may be equipped with an optional Digital Input Output Board which has three or six potential

free Form C relay contacts and three opto-isolated digital inputs. A terminal block as shown in Figure 2-8

below is provided for the three alarm output Potential Free Form C connections: Normally Open (NO),

Common (C), and Normally Closed (NC), and the three digital inputs which share a common. The relay

contacts are capable of switching 125 Vac ~ at 0.5 Amp or 30 Vdc at 0.5 Amp. The potential free relay

contacts are protected internally with 300 volt Metal Oxide Varistors (MOVs) to prevent contact arcing.

The Recorder may be equipped with an optional Digital Input Output Board which has three or six solid

state open collector outputs and three opto-isolated digital inputs. A terminal block as shown in Figure

2-9 below is provided for the alarm output connections. The output connections are polarized and are

intended for DC operation only. Reverse polarity protection is provided and each output is fused at 1 Amp.

The fuse is solid state and will reverse once the load is removed. The outputs are rated at 30 VDC at 0.5

Amp and are optically isolated from the Recorder.

The opto-isolated inputs require an external potential of 5 to 12 volts DC @ 10 milliAmps. The three inputs

are isolated from the unit, but not from each other as they share a common. The positive voltage connects

to the terminals marked 1, 2 or 3 and the common connects to the terminal marked C. It is possible to use

potential free contacts to operate the digital inputs. This requires opening the unit and setting jumpers on

the relay board. Refer to Appendix E - Setting the Jumpers for the 3 or 6 Channel Mechanical or Solid State

Relay for details.

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Figure 2-8 Mechanical Relay Connections (3 Channel Shown)

Figure 2-9 Solid State Relay Connections (3 Channel Shown)

Page 2-8

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