Teledyne 3190Z - Zirconium oxide trace oxygen analyzer - Manual (Page 23)

Trace Oxygen Analyzer Installation
Teledyne Analytical Instruments 15
Alarm Relays: The three alarm circuit connectors are screw terminals
for making connections to internal alarm relay contacts. There is one set
of contacts for each type of alarm. Contacts are Form C, with normally
open and normally closed contact connections capable of switching up
to 0.5A at 125 VAC into a resistive load.
The alarm relay circuits are designed for failsafe operation,
meaning the relays are energized during normal operation. If power fails
the relays de-energize (alarms activated).
The contact connections are indicated diagrammatically on the rear
panel as normally closed (NC), common (C), and normally open (NO).
Figure 3-3 explains how these act in failsafe operation.
The specific descriptions for each type of alarm are as follows:
HI Alarm Configured as high alarm (actuates when
concentration is above threshold). Can be set
anywhere within the full range of the analyzer (1-
1,000 ppm), but must be set ABOVE the threshold set
for the LO Alarm.
LO Alarm Configured as low alarm (actuates when
concentration is below threshold). within the full
range of the analyzer (1-1,000 ppm), but must be set
BELOW the threshold set for the HI Alarm.
Sensor Fail Not active in this product
Figure 3-3: Contact ID for FAILSAFE Relay Operation