Teledyne 2020 - Explosion proof thermal conductivity analyzer - Manual (Page 51)

Thermal Conductivity Analyzer Operation 4
4-17 Teledyne Analytical Instruments
plings and displays this difference as Slope on the screen. It takes several
seconds for the first Slope value to display. Slope indicates rate of change of
the Span reading. It is a sensitive indicator of stability.
####.##% H2 — N2
Slope=#.### Span
When the
Span value displayed on the screen is sufficiently stable,
press Enter . (Generally, when the
Span reading changes by 1 % or less of
the range being calibrated for a period of ten minutes it is sufficiently sta-
ble.) Once
Enter is pressed, the
Span reading changes to the correct value.
The instrument then automatically enters the Analyze function.
4.5 The Alarms Function
The Model 2020 is equipped with 6 fully adjustable set points concen-
tration with two alarms and a system failure alarm relay. Each alarm relay
has 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 fail-safe or non-fail-safe, 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
contaminant concentration rises above the setpoint. Setting an
alarm as LOW triggers the alarm when the contaminant
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?