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Note that adjusting R18 affects both alarm recognition time (time for the TX switch to recognize an alarm condition at
the sensors) as well as recovery time (time for the TX switch to recognize that the conditions have returned to normal)
by positioning the "alarm/recovery" window nearer the alarm or normal process condition mV values. Note: it is impor-
tant to allow 5+ minutes of stabilization in any new process condition to obtain repeatable time values.
1. If the alarm entry time needs to be made faster AND the alarm recovery time (time to return to normal condi-
tions) needs to be made slower, turn R18 CCW in ½-1 turn increments, moving the alarm/recovery window
nearer the Alarm (Low TC; High mV) process condition.
2. If the alarm recovery time (time to return to normal energized state) needs to be made faster AND the alarm
entry time needs to be made longer, turn R18 CW in ½ - 1 turn increments. This moves the alarm/recover
window closer to the Normal (High TC; Low mV) process condition.
3. Test the switch response after each adjustment until an acceptable balance in alarm entry time vs. recovery
time (return to normal conditions) is established empirically.
3.2 Calibrate from Low TC (Thermal Conductivity) process conditions as follows:
JP3 State B - Green LED, output relay energized at NORMAL condition (LOW Thermal Conductivity, high differential
temperature, conditions at the sensors); low level (level below sensor), flow below set point (see table page 6)
Notes:
1. If the TX switch is operated in State B, the TX switch should be adjusted (calibrated) in the ALARM condi-
tion; Highest Thermal Conductivity conditions on the sensors (wet sensor, high flow); Green LED and output
relay will be de-energized during and after calibration.
2. CCW rotation of R18 turns LED ON.
Calibration Adjustments
1. Provide the ALARM condition (High Thermal Conductivity process condition (high level (level above sensor),
high flow condition)) at the sensor. Green LED and output relay will be de-energized after calibration adjust-
ments
2. Allow 5 minutes (minimum time) for switch temperature to stabilize.
3. Adjust R18 (see drawing page 5) as follows:
A. If LED is On – slowly turn R18 clockwise (CW) until the green LED turns OFF
B. If LED is Off – slowly turn R18 counter clockwise (CCW) until the green LED turns on – then slowly CW
until it just turns OFF.
4. Turn R18 CW as follows for stable operation (no false alarms) (LED will be Off):
A. Air – ¼ turn
B. Organics/Hydrocarbons – ½ turn
C. Water – 1 full turn
3.3 Trimming the TX settings for optimum alarm entry/return to normal time balance if required:
When the R18 is adjusted such that the LED just turns off, (3.a/b. above), the TX "alarm/recovery (return to normal)
window" is positioned nearest to the process's de-energized LED Alarm (high TC; Low mV) value. This provides the
shortest possible recovery time to recognize the energized LED Normal condition, but the longest possible time to
enter the de-energized (Alarm) state.
Step 4 is an attempt to provide somewhat equal response times (time to enter alarm vs. time to recognize normal con-
ditions and exit the alarm condition) as well as stability from false alarms. Note that adjusting R18 affects both alarm
recognition time (time for the TX switch to recognize an alarm condition at the sensors) as well as recovery time (time
for the TX switch to recognize that the conditions have returned to normal) by positioning the "alarm/recovery" window
nearer the alarm or normal process condition mV values.
Note: it is important to allow 5+ minutes of stabilization in any new process condition to obtain repeatable time val-
ues.
1. If the alarm entry time needs to be made faster AND the alarm recovery time (time to return to normal condi-
tions) needs to be made slower, turn R18 CW in ¼ - ½ turn increments. Test the switch response after each
adjustment until an acceptable balance in alarm entry time vs. recovery time (return to normal conditions ) is
established empirically.
6 TX Thermal Disperson Level Switches | Operating instruction manual
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