15
54-610 Thermatel
®
Model TD1/TD2 Flow Level Switch
2.6.4 Advanced Calibration Procedure (TD2 only)
Measure and record the voltage between TP1 and TP2.
This voltage will change as the set point potentiometer is
adjusted. Voltage readings will be between 0 and 5 VDC.
This value may be used for future reference or adjustment
of set point. This value can be recorded and checked in the
future to ensure that the set point has not changed since
last calibration.
NOTE: Due to ATEX requirements, these test points (TP1 and TP2)
are not provided on units for Zone 0 service.
3.0 Reference Information
3.1
Description
THERMATEL TD1/TD2 switches are used for flow,
level, and interface detection and control. Level detection
is accomplished by sensing changes in the heat transfer char-
acteristics of the media. Flow detection is accomplished by
sensing changes in heat transfer caused by the flowing media.
The TD1 is the basic version while the TD2 offers
advanced options including LED indication of flow/level,
optional remote electronics, mA output representing the
sensor signal, time delay, and a voltage signal representing
the set point of the unit.
Sensors are available in 316/316L stainless steel, Hastelloy
®
C,
or Monel
®
welded construction. The easy-to-install and
adjust units provide reliable, low maintenance performance
in the most demanding applications.
Both switches have continuous diagnostics to detect a
failure of the sensor. This is accomplished by continuously
monitoring the signal from the sensor which must remain
within set levels. In the event the switch detects a fault,
the relay will de-energize and the red LED will blink.
3.2
Theory of Operation
The THERMATEL Flow/Level Switch consists of a dual
element sensing assembly mounted integrally to the elec-
tronics, or the sensor may be remote mounted up to 500
feet (150 meters) from the electronics (TD2 only).
