Horn Relay
• This Single-pole, single-throw (SPST), normally-open (N/O)
relay works in parallel with the instrument horn.
• These contacts are open when the instrument horn is OFF or
not selected for operation [see FIGURE 1-6 for terminal block
(TB9) location].
• The contacts:
• close when the instrument horn activates
• remain closed until the horn is de-activated due to:
• elimination of the hazardous condition
• pressing the HORN ACKNOWLEDGE button.
Relay Wiring with Inductive Loads
If you are connecting the relays to motors, fluorescent lighting or
other inductive loads, it is necessary to suppress any sparks that
may occur at the relay contact. These sparks will deteriorate or
destroy the relay contacts, rendering the relay inoperative or
useless. One way to reduce this destructive sparking is to install
a Quencharc protector (MSA P/N 630413) across the contacts.
Milliamp Output
The Toxgard II Monitor may be connected to any device capable
of accepting 4 to 20 mA analog signals such as the:
• MSA Model 5000 Monitor
• MSA Quad Gas unit
• Programmable controllers
• DCS’s, etc.
The standard unit is supplied with a non-isolated, 4-20 mA signal.
An isolated 4-20 mA output option is also available.
Figure 1-7.
Standard 4-20 mA Terminal Wiring
Chapter 1, Set-up
1-14
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