Magnetrol Echotel 961/962 Ultrasonic Level Switches

Magnetrol Echotel 961/962 Ultrasonic Level Switches meet these demands with reliable transducer designs, extensive hazardous location approvals, and advanced self-test technology. Increasing demands for compliance with safety systems and overfill protection has mandated more reliable point-level measurement.

Model 961 offers the ultimate solution to reliable single-point liquid level measurement. This advanced switch uses pulsed signal technology for superior performance in difficult process conditions, and to provide excellent immunity from sources of electrical noise interference. Extensive self-testing of the electronics and transducer make this advanced switch suitable for use in Safety Integrity Level (SIL) 2 loops.

Model 962 is a dual point switch that can be used as a level controller or to control pumps in an auto-fill or auto empty mode. The tip-sensitive lower gap performs well in aerated or foamy liquids, and can measure to within 1 ⁄4″ of the vessel bottom. The rigidity of the unique flow-through upper gap allows separations of up to 127″ (322 cm) between the upper and lower transducer gaps.

Magnetrol Echotel 961/962 Features

• No calibration required
• Performance independent of liquid type or properties such as density (SG)
• Single or dual point liquid level measurement
• Advanced self-test and diagnostics
• Adjustable time delay for turbulent or aerated liquids
• Relay output or mA current shift with separate malfunction indication
• Integral or remote mount electronics
• Pulsed signal technology
• FM, CSA, ATEX and IEC agency approvals
• Suitable for Safety Integrity Level (SIL) 1 and 2 loops

Applications

• Overfill protection
• Seal pot level
• High/low-level alarm
• Chemical Tanks
• Pump protection/control
• Low density/low dielectric
• Cryogenic liquids
• Level with spray balls
• Fill lines

Basic Operation

Model 961/962 switches utilize ultrasonic energy to detect the presence or absence of liquid in a single or dual point transducer. Ultrasonic contact level technology uses high frequency sound waves that are easily transmitted across a transducer gap in the presence of a liquid media, but are attenuated when the gap is dry. Model 961/962 switches use an ultrasonic frequency of 2 MHz to perform this liquid level measurement in a wide variety of process media and application conditions.

The transducer uses a pair of piezoelectric crystals that are encapsulated in epoxy at the tip of the transducer. The crystals are made of a ceramic material that vibrates at a given frequency when subjected to an applied voltage. The transmit crystal converts the applied voltage from the electronics into an ultrasonic signal. When liquid is present in the gap, the receive crystal senses the ultrasonic signal
from the transmit crystal and converts it back to an electrical signal. This signal is sent to the electronics to indicate the presence of liquid in the transducer gap. When there is no liquid present, the ultrasonic signal is attenuated and is not detected by the receive crystal

PULSED SIGNAL TECHNOLOGY

Challenging process conditions such as aeration, suspended solids, and high viscosities are easily handled with the pulsed signal technology utilized in the 961/962 switches. Pulsed signal circuitry drives the transmit piezoelectric crystal to produce powerful pulses of high-frequency ultrasonic energy. These ultrasonic pulses are readily transmitted through liquids, but are attenuated when the transducer gap is dry. This technology also provides excellent immunity from electromagnetic noise interference.

Pulsed signal technology makes the 961/962 units more reliable than older continuous wave ultrasonic switches. Unlike many tuning forks, pulsed signal ultrasonic switches do not need to be configured for different media densities, making these units the most universally applied level switches on the market today.

ADVANCED SELF – TEST AND DIAGNOSTICS

Ultrasonic switches are often used as the 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 generated to alarm the user, and a red LED is lit to indicate a diagnostic alarm condition.

Self-test is performed automatically and continuously several 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 technologies. 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 microprocessor 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:

• One flash of the Fault LED indicates a problem with the transducer or piezoelectric crystals
• Two flashes of the Fault LED indicates a problem with one of the electronics boards
• Three flashes of the Fault LED indicates excessive levels of environmental noise

APPLICATIONS

TYPICAL

Model 961 single point switches may be used for high or low level alarm, as well as for pump protection. The Model 962 dual point unit is typically configured to measure high/low, high/high, or low/low levels. Comman applications include safety-critical high-level alarms to conform to API 2350 or seal pot level to conform to API 682.

The single point 961 can be mounted vertically or horizontally in vessels, bridles, or pipes. The dual gap 962 is always top mounted.

A broad selection of transducer materials allow the 961/962 to be used in a wide variety of process media. Metallic transducers include 316 SS, Hastelloy® C, and Monel ®. The 316 SS transducer has a NACE construction option for sour gas service, and can also be built per ASME B31.1 and B31.3 piping codes. Thermoplastic transducers include Kynar® and CPVC. These corrosion resistant plastic transducers feature a stiffening tube that runs the length of the transducer for extra rigidity. Kynar-faced 316 SS flange options are offered with the Kynar transducers.

PUMP CONTROL

A DIP switch on the Model 962 allows it to be configured to control level, or to function as a pump controller. In the pump control mode the unit can perform auto fill or auto empty of tanks, sumps, or wet wells. The tip sensitive lower gap allows liquid levels to be pumped down to within 1 ⁄4″ from the bottom of the vessel. The rigidity of the flow through upper gap allows the 962 to be used even
when sumps experience severe turbulence from vessel fill lines.

Specifications

Download Datasheet: Magnetrol Echotel® 961/962 Single- And Dual-point Ultrasonic Level Switches

Reference: magnetrol.com

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