961-20A0-011 Datasheet, PDF (3/12 Pages) Magnetrol International, Inc. – Echotel® Model 961/962 Ultrasonic Level Switches

ADVANCED SELF-TEST AND DIAGNOSTICS
Ultrasonic switches are often used as the
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Electronics
Noise
last means of detecting whether a
process vessel will overflow and cause a
spill of potentially hazardous liquids, or
empty out and possibly cavitate the
pumps. In these critical applications it is
desirable to have a method of periodically testing the
ultrasonic switch to ensure that it is functioning properly.
Model 961/962 switches feature an advanced self-test
technology that not only tests the electronics, transducer,
and piezoelectric crystals, but also tests for the presence
of industrial sources of environmental noise. Should the
switch detect any problems a malfunction output is gen-
erated to alarm the user, and a red LED is lit to indicate
an alarm condition.
Self-test is performed automatically and continuously sev-
eral times per second to verify proper operation of
961/962 switches. In addition, a pushbutton is provided to
initiate a manual self-test mode. Pressing this test button
stops all transmit pulses, which simulates an electronics
failure. This failure is reported as:
• 3.6 or 22 mA (selectable) with current shift output units
• SPDT malfunction relay de-energizes with relay
output units
Taking diagnostics one step further is the unique noise
self-test mode feature that is standard in all 961/962
switches. This tests for electromagnetic and acoustical
noise that can influence many instrumentation technolo-
gies. If high levels of environmental noise are detected,
the electronics reports a fault condition to alert the user
of potential instrumentation reliability concerns.
A microprocessor in the 961/962 electronics continuously
monitors all self-test data. Should a fault occur, the micro-
processor can determine whether the malfunction is due
to the electronics, transducer, piezoelectric crystals, or the
presence of environmental noise. A pushbutton and Fault
LED is used to assist in troubleshooting the switch:
5 One flash of the Fault LED indicates a problem
with the transducer or piezoelectric crystals
55 Two flashes of the Fault LED indicates a
problem with one of the electronics boards
555 Three flashes of the Fault LED indicates
excessive levels of environmental noise
ADJUSTABLE TIME DELAY
Turbulence and splashing can cause
some fixed time response switches to
produce false level alarms. Model
961/962 switches overcome this difficulty
with an adjustable time delay feature.
A potentiometer allows a ¹â„2 to 45 second delay to be set
to disregard waves or splashes, and reliably detect the
true liquid level.
RELIABLE TRANSDUCER DESIGN
Dependable point level measurement
begins with reliable sensor design. Over
30 years of ultrasonic level switch tech-
nology experience is behind the Model
961/962 single and dual gap transducers.
The result is an extremely robust trans-
ducer design that offers superior perform-
ance in difficult process conditions.
Model 961 single point has a tip-sensitive transducer with
an arch-shaped gap for superior performance in aerated
or foamy liquids. Dual point Model 962 features a tip sen-
sitive lower gap and flow through upper gap. This robust
design allows separations of 125 inches (318 cm) between
the upper and lower transducer gaps.
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