Monarch Instrument DC 2000 - Manual (Page 26)

Page 2-8
Chapter 2 Installation and Wiring
2.3.4 Relay Output, Contact Input
WARNING
To prevent the possibiltiy 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).
2.3.4.1 Mechanical Relay Option
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 2 Amps. The potential free relay
contacts are protected internally with 300 volt Metal Oxide Varistors (MOVs) to prevent contact arcing.
Figure 2-8 Mechanical Relay Connections (3 Channel Shown)
2.3.4.2 Solid State Relay Option
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.
Figure 2-9 Solid State Relay Connections (3 Channel Shown)
2.3.4.3 Opto-isolated Inputs/Outputs
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 A for details.