4 Operation Model 3020T
4-14 Teledyne Analytical Instruments
When the Span value displayed on the screen is sufficiently stable,
ENTER it. (Generally, when the Span reading changes by 1 % or less of the
full scale of the range being calibrated for a period of ten minutes it is suffi-
ciently stable.) Once you ENTER it, the Span reading changes to the correct
value. The instrument then automatically enters the ANALYZE function.
4.9 The ALARMS Function
The Model 3020T is equipped with 2 fully adjustable concentration
alarms and a system failure alarm. Each alarm has a relay with a set of form
“C" contacts rated for 3 amperes resistive load at 250 V ac. See Figure in
Chapter 3, Installation and/or the Interconnection Diagram included at the
back of this manual for relay terminal connections.
The system failure alarm has a fixed configuration described in chapter
3 Installation.
The concentration alarms can be configured from the front panel as
either high or low alarms by the operator. The alarm modes can be set as
latching or non-latching, and either failsafe or non-failsafe, or, they can be
defeated altogether. The setpoints for the alarms are also established using
this function.
Decide how your alarms should be configured. The choice will depend
upon your process. Consider the following four points:
1. Which if any of the alarms are to be high alarms, and which if
any are to be low alarms?
Setting an alarm as HIGH triggers the alarm when the oxygen
concentration rises above the setpoint. Setting an alarm as LOW
triggers the alarm when the oxygen concentration falls below the
setpoint.
Decide whether you want the alarms to be set as:
• Both high (high and high-high) alarms, or
• One high and one low alarm, or
• Both low (low and low-low) alarms.
2. Are either or both of the alarms to be configured as failsafe?
In failsafe mode, the alarm relay de-energizes in an alarm
condition. For non-failsafe operation, the relay is energized in an
alarm condition. You can set either or both of the concentration
alarms to operate in failsafe or non-failsafe mode.
3. Are either of the alarms to be latching?
In latching mode, once the alarm or alarms trigger, they will
remain in the alarm mode even if process conditions revert back