CONFIGURATION
Part. No. 2400M2501_6 Touchpoint Pro
92 Technical Handbook
10 Configuring STEL and LTEL Alarms
TPPR mA channels may be configured as STEL and LTEL alarms. The same channel may be used for both STEL and
LTEL.
STEL and LTEL are always rising alarms, and are latched by default.
Note: STEL and LTEL Alarms should always be set to Latching. A non-latching alarm may reset before the appropriate
actions can be taken.
A channel programmed for STEL and/or LTEL may not be used for threshold alarms (A1, A2, and A3). When connected to
an output cause and effect matrix, STEL replaces A1, LTEL replaces A2, and the rate alarm replaces A3.
In common with other alarms, STEL and LTEL alarms cannot be reset if an Over Range Warning is active. The Over Range
Warning must be cleared first.
10.1 STEL Operation
The controller takes four gas readings every second. Readings are rolled up and averaged over the configured STEL
interval.
The averaged STEL value is updated every half minute and compared against the programmed STEL limit.
The STEL alarm is activated if the calculated result is above the programmed threshold.
The average is calculated continuously while the system is powered.
The averaged value is initialised to a default value:
when power is applied
when there is a change in STEL configuration
when the alarm is reset by a user
The default value is equal to the Gas Range Minimum configured for the channel. Following initialisation, the calculation
requires one STEL interval to stabilise.
When the channel is inhibited, the controller continues to calculate the average but uses the above default value instead of
the sensor value. The channel will not alarm while inhibited.
The alarm cannot be reset until the averaged value falls below the programmed threshold. The time to wait before you can
reset will depend upon the degree of ventilation, the residual gas levels and the programmed settings.
Note: The STEL Interval is configurable from 5 – 20 minutes in 5 min. increments, from 20 – 40 minutes in 10 min.
increments and finally to 60 minutes.
WARNING
STEL AND LTEL HISTORY IS RESET WHEN POWER IS REMOVED. THE READING WILL REQUIRE AN
INITIALIZATION TIME AFTER POWER IS RESTORED.
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