Span Failure; The Alarms Function - Teledyne 3000TB Instruction Manual

4 Operation
Once the span has begun, the microprocessor samples the output at a
predetermined rate. It calculates the difference between successive samplings
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.
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 full scale of the range being calibrated for a period of ten minutes it is
sufficiently stable.) Once Enter is pressed, the Span reading changes to the
correct value. The instrument then automatically enters the Analyze func-
tion.
4.4.3

Span Failure

The analyzer checks the output of the cell at the end of the span. If the
raw output of the cell is less than 0.5 uA/ppm O
accepted. The analyzer will return to the previous calibration values, trigger
the System Alarm, and display in the VFD:
Span Failed!!
This message will be shown for five seconds and the instrument shall
return to the Analyze mode. In the upper right hand corner of the VFD
display "FCAL" will be shown. This message flag will help the operator
troubleshoot in case calibration was initiated remotely. To reset the alarm
and the flag message, the unit must be turned off by cycling the standby key
. It will not reset if the next span cycle is correct.
A trace cell is unlikely to fail span. As explained before, when the
sensor reaches the end of its useful life, the zero offset begins to rise until the
analyzer finds the zero unsatisfactory. Nevertheless, feeding the wrong span
gas or electronics failure could set this feature off at the end of the span.
Consider this before replacing the cell.
4.5

The Alarms Function

The Model 3000TB 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
4-16
#### % Span
Slope=#### ppm/s
Teledyne Analytical Instruments
, the span will not be
2
Model 3000TB