E C H O T E L ® C O N T A C T U L T R A S O U N D

Worldwide Level and Flow Solutions SM

®

MAGNETROLCONTACT ULTRASOUND

The Total Spectrum of Solutions

Magnetrol products employ a number of

technologies to meet the challenges of

level and flow measurement. Echotel

contact ultrasonic switches utilize

continuous wave and pulsed signal

ultrasound for accurate and reliable

liquid level measurement.

▼

Magnetrol International—a world

leader in level and flow meas-

urement technology—designs, manu-

factures, markets and services level

and flow instrumentation worldwide.

Magnetrol’s product groups are

based upon these technologies:

• Air Sonar

• Buoyancy

• Contact Ultrasound

• Guided Wave Radar

• RF Capacitance

• Thermal Dispersion

• Vibration

• Visual Indication

The industries we serve include:

• Petroleum Production

• Petroleum Refining

• Power

• Petrochemical

• Chemical

• Water & Wastewater

• Pulp & Paper

• Food & Beverage

• Pharmaceutical

3

An Introduction to Ultrasonic Level Sensing

• Continuous-Wave and Pulsed-Signal Sensing

• Self-Test Capabilities

• Application Guidelines

• Advantages and Limitations of Ultrasonic Sensing

Echotel Contact Ultrasound Product Line

• Model 910

• Models 911 and 921

• Models 915P and 915W

• Models 919F and 919R

• Models 91S and 92S

• Hot Tap Assembly for Echotel

4

6

7

9

11

8

10

An Introduction To Contact Ultrasonic Level Sensing

4

Contact ultrasonic level switchesuse ceramic discs called piezoelec-tric crystals to transmit and receiveultrasonic energy. A transmit crys-tal (T) is on one side of a transducergap and a receive crystal (R) is onthe opposite side. Tip-sensitive stylegaps (left) can sense level within 1⁄4"from the end of the transducer, whilethe side-gap style (right) must becompletely filled with fluid beforeliquid level is sensed.

T

T

R R

Ultrasound technology was developed during

WWII under the acronym SONAR (SOund

Navigation And Ranging). Ultrasonic level

measurement entered the process control industry in

the 1960s and today it continues to play a significant

role in liquid level measurement and control.

Ultrasonic level instruments fall into two groups:

Those which are designed for non-contact sensing and

those which come into direct con-

tact with process media. This

brochure focuses on Magnetrol’s

contact instruments which are

used for point level measurement.

Continuous-Wave and

Pulsed-Signal Sensing

Contact liquid level sensing is

achieved by one of two ultrasonic

technologies: Continuous-Wave or

Pulsed-Signal technology.

Continuous-Wave switches have

two piezoelectric crystals mounted opposite each other

in a transducer body, separated by a gap. The transmit

crystal produces an acoustical signal when subjected to

an applied voltage from an amplifier circuit. The

receive crystal converts the acoustical signal it receives

into an electrical signal, which becomes the input of

the same amplifier circuit. When liquid is present in

the transducer gap, the amplifier becomes as oscillator

causing a relay circuit in the electronics to indicate a

wet gap condition. When liquid vacates the gap, the

amplifier returns to an idle state.

In Pulsed-Signal units a digital electronic amplifier

produces a powerful pulse of

ultrasonic energy five to ten times

more powerful than most continu-

ous wave units. This allows meas-

urement in conditions that include

aeration, suspended solids, turbu-

lence, and highly viscous liquids.

Pulses of high-frequency

ultrasonic energy milliseconds in

duration are produced by the

transmit crystal. In between each

pulse the receive crystal “listens”

for the transmission. If liquid is

present in the gap the receive crystal detects the pulse

and reports a wet gap condition to the electronics.

When the gap is filled with air, the receive crystal

cannot detect the pulse, and reports a dry gap condition.

Challenging process conditions such assuspended solidsor aeration are bestmanaged by pulsed-signal ultrasoniclevel switches. The effects of mildturbulence canbe minimized bychoosing a switchwith an adjustabletime-delay circuit.

5

Self-Test Capabilities

An ultrasonic switch is often used as the last means

of detecting whether a vessel will overflow and cause

a spill, or empty out and possibly cavitate the pumps.

In these critical applications a method of periodically

testing the ultrasonic switch to ensure proper function-

ing is desirable.

Several Echotel units offer self-test capabilities that

can be performed automatically several times per

second or manually with a magnet or push button. An

advanced self test is also offered on several pulsed

technology units to test bonding integrity of the

piezoelectric crystals to the transducer gap.

Application GuidelinesContact ultrasonic level switches are not affected by

changes in liquid properties such as

specific gravity, conductivity, pH, and

dielectric or temperature shifts.

Turbulent liquid applications can

cause false level alarms, especially if

the process media is a viscous liquid

with suspended solids. Echotel switches

remedy this by offering time delay

circuitry and through the use of a tip-sensitive trans-

ducer design. Several units offer an adjustable time

constant that resolves false alarms with rising and/or

falling liquid levels. Tip-sensitive transducers drain

liquids and air bubbles more efficiently from the sensor

gap, and are more reliable in difficult process conditions.

Advantages and Limitations

The advantages of contact level sensing are:

• Low cost single and dual-point sensing.

• Accurate and reliable in a variety of liquids.

• Easy installation and simple configuration.

• A broad range of sensor materials are available.

• Transmits a stable signal despite

liquid property changes.

• Switches contain no moving parts

for long life and low maintenance.

Certain process conditions may interfere with the

ultrasonic signal. These conditions include:

• Slurries with a very high percentage of solids.

• Extreme aeration of the liquid.

• Media which generate crystallized coatings.

• Aggressive turbulence and splashing. ■

Ultrasonic Level Measurement Solutions for Every Industry

MODEL ULTRASOUND TECHNOLOGY SET POINTS SENSOR STYLE MOUNTING 3A VERSION SELF-TEST TIME DELAY

910 Continuous Wave Single Tip Integral

911 Continuous Wave Single Side Integral or Remote ■ ■

921 Continuous Wave Dual Side Integral or Remote ■ ■

915W Pulsed Signal Single Tip Integral ■

915P Pulsed Signal Single Tip Integral ■

919F Pulsed Signal Single Tip Integral ■

919R Pulsed Signal Single Tip Integral ■

91S Pulsed Signal Single Tip Integral or Remote ■ ■

92S Pulsed Signal Dual Side Integral or Remote ■ ■

At a Glance: Magnetrol’s Agency-Approved Ultrasonic Switches

Tip-SensitiveTransducer

6

910 Level Switch

An industry leader featuring a 10 amp DPDT goldflash relay field-selectable for high or low level fail-safe. Worldwide safety approvals, 2-year warranty.

Proximity SensingThe Model 910 measures liquid levelwithin 0.25" (6 mm) from the end of thetip-sensitive transducer. When used asa low level switch, it can measure levelfurther down into a tank or vessel.

Omni-Directional MountingModel 910 may be mounted horizontallyor vertically. Mounting options includeNPT and BSP threaded, flanges andsanitary connections.

Worldwide Safety ApprovalsWith FM, CSA and CENELEC approvalson one agency nameplate, this is the perfect switch for OEM applications withglobal customer destinations.

PROCESS MEDIA:

• Clean liquids

• Low viscosity liquids

• Liquids with low % solids

• Corrosive liquids

OF SPECIAL INTEREST TO:

• Wastewater treatment

• Oil and gas industry

• OEM and skid manufacturers

Liquid Level Applications

Model 910

Model 910 Electrical Specifications

Power Supply 120 VAC (+10%/-15%), 50/60 Hz

240 VAC (+10%/-15%), 50/60 Hz

24 VDC (±10%)

Power Consumption 2.5 VA nominal

Relay Output

Gold Flash DPDT, 10 amps @ 120 VAC,

240 VAC, or 24 VDC

Hermetically-Sealed DPDT, 5 amps @120 VAC,

240 VAC, 24 VDC

Repeatability 0.078" (2 mm)

Fail-Safe Field selectable high or low

Ambient Temperature

Electronics -40° to +160° F (-40° to +71° C)

Process Temperature

Transducer -40° to +250° F (-40° to +121° C)

Operating Pressure 800 psig (55 bar) maximum

911/921Level Switch

Single and dual point continuous wave ultrasonicswitches for liquid applications having low vis-cosity, low aeration and low percent of solids.

Single and Dual Gap ModelsThe Model 911 (single gap) and Model 921 (dualgap) are available in a broad choice of transducermaterials that between them include 316 StainlessSteel, CPVC, Hastelloy B or C, Kynar, Monel,Polypropylene, and Teflon.

Adjustable Time Delay and Self-TestAn adjustable time delay compensates forsplashing or turbulence of the processfluid. Both models 911 and 921 featurelocal and remote self-test capabilities.

Integral or Remote ElectronicsModels 911 and 921 are available with integral orremote electronics. The single-gap model 911 canbe mounted horizontally or vertically. The dual-gapmodel 921 is always top-mounted.

PROCESS MEDIA:

• Clean liquids

• Low viscosity liquids

• Light slurries

• Acids and caustics

OF SPECIAL INTEREST TO:

• Chemical plants

• Hydrocarbon processors

• Power generation

7

Liquid Level Applications

Model 911/921 Electrical Specifications

Power Supply 120 VAC, 50/60 Hz (+10%/-15%)

240 VAC, 50/60 Hz (+10%/-15%)

24 VDC, (±10%) 12 VDC, (±10%)

Output Signal

Gold Flash Relay DPDT, 10 amps @ 120 VAC,

240 VAC, or 24 VDC

Hermetic Relay DPDT, 5 amps @ 120 VAC,

240 VAC, or 24 VDC

Power Consumption 2.5 VA nominal

Repeatability 0.078" (1.98 mm)

Fail-Safe Field selectable high or low

Time Delay 0 - 60 seconds nominal

Self Test Local magnetic or jumper

Remote by push button

Ambient Temperature -40° to +160° F (-40° to +71° C)

Process Temperature -40° to +250° F (-40° to +121 °C)

Operating Pressure 800 psig (55 bar) maximum

Above: Singlepoint model 911Right: Dual pointmodel 921

Model 915 Electrical Specifications

Power Supply 10–35 VDC (24 VDC nominal)

Power Consumption 1 watt maximum

Signal Technology Pulse (electronic windowing)

Output Normal Operation 16 mA ±1 mA

Alarm Condition 8 mA ±1 mA

Malfunction 5 mA ±1 mA

LED Indication Normal Green LED on

Alarm Red LED on

Malfunction No LED’s on

Response Time 0.15 second typical

Repeatability ±0.078" (2 mm)

Ambient Temperature -40° to +160° F (-40° to +70° C)

Process Temperature

915P -40° to +300° F (-40° to +150° C)

915W -40° to +250° F (-40° to +120° C)

Maximum Pressure

915P 1500 psig @ +300° F (103 bar @ +150° C)

915W 100 psig @ +250° F (7 bar @ +120° C)

8

915 Level Switch

Hi-Performance UltrasoundPulsed signal technology offers superior perfor-mance in difficult conditions (aeration, foaming,suspended solids); and provide immunity fromnoise interference. The surface mount electronicsare completely encapsulated in a potted modulefor maximum protection.

Choice of Transducer MaterialsModel 915P is available with 316 stainless steel,Hastelloy C, or Monel transducers.

Model 915W is available with a Kynar transducerin a 3⁄4" NPT and Kynar faced-flange options.

Continuous Self-Test The continuous self-test performs a diagnosticcheck of electronics, transducer and piezoelectriccrystal bond integrity several times per second inboth wet and dry gap conditions.

Two-wire, loop powered integral switchesutilize pulsed signal technology to detecthigh or low level in a broad range of liquids.

CONTROL FUNCTIONS:

• High/Low level alarm

• Overfill protection

• Pump protection

• Leakage detection

• Tank fill monitoring

• Valve actuation

Liquid Level Applications

Above: 915P with316 SS transducerand flange. Right: 915W withKynar transducer.

919 Level Switch

A pulsed signal ultrasonic switch in a compact,integral Valox® housing that performs high or lowlevel control in a variety of liquid applications.

Choice of ElectronicsYour choice of electronics is housed in a watertight,corrosion resistant Valox housing that’s rotatable for easyconduit alignment. Model 919R is a 24 VDC unit featur-ing a 3 amp SPDT relay output. Model 919F is an all-volt-age version that operates from 24 to 240 volts AC or DC.

Pulsed Signal TechnologyPulsed signal technology excels in difficult conditions thatmay cause other ultrasonic switches to falter. The tech-nology also provides excellent immunity from electricalnoise that is common in many industrial applications.

3-A Authorized Sanitary VersionThe 3-A authorized sanitary transducer option has a20 Ra surface finish and a unique, crevice-free sensor tipthat enhances cleanability during the Clean-In-Placeprocess. All transducers may be mounted horizontally orvertically.

CONTROL FUNCTIONS:

• High/Low level alarm

• Overfill protection

• Pump protection

OF SPECIAL INTEREST TO:

• Food & Beverage

• Pharmaceutical

• Generic chemicals

• Biotechnology

9

Liquid Level Applications

Model 919 withSanitary Flange

Model 919 Electrical/Environmental Specifications

Power Supply

All Voltage 24-240 VAC ±10% 50-60 Hz

24-240 VDC ±10%

Relay 24 VDC (±10%)

Power Consumption

All Voltage 0.1 VA maximum

Relay Less than 1 watt

Signal Output

All Voltage 500 mA (continuous) maximum

7.5 mA (continuous) mininimum load

Relay SPDT 3 amp @ 30 VDC resistive and

3 amp @ 125 VAC resistive

Repeatability 0.078" (2 mm)

Response Time 1⁄2 second typical

Ambient Temperature

Electronics -40° to +160° F (-40° to +70° C)

Process Pressure 1500 psig (103 bar) maximum

Process Temperature

Without Heat Extension -40° to +250° F (-40° to +120° C)

With Heat Extension -40° to +300° F (-40° to +150° C)

10

91S/92STRIDENT®

Level Switch

Available with a current shift or 10 amp DPDT relayoutput, Trident single and dual-point switches offeran advanced, continuous self-testing technology.

Choice of Electronics Current-Shift Version is a 24 VDC switch thatproduces an 8mA output without liquid in thegap, and 16mA with liquid in the gap.There isalso a field-selectable malfunction output ofeither 5mA or 19mA for fault conditions.

Relay Version has a 10 amp, DPDT gold flashprocess relay(s) and a dedicated 10 amp SPDTgold flash malfunction relay.

Continuous Self-TestThe self-test function continuously tests theintegrity of the electronics, transducer andpiezoelectric crystal bond. The self-test can alsorun manually by pushing a button on the PCboard—or, remotely, by wiring an external push-button to a terminal block provided on the unit.

Adjustable Time DelayTo contend with turbulent process conditions,Trident switches incorporate a time-delayfeature. The delay is adjustable from half asecond to a full 30 seconds and can be set forrising or falling tank levels.

CONTROL FUNCTIONS:

• High or Low level alarm

• Overfill protection

• Pump control & protection

• Seal pot level

Liquid Level Applications

Model 91S

Model 92S

Trident Relay Specifications

Supply Voltage 12, 24, or 48 VDC (±10%) 120 or

240 VAC (+10%/-15%), 50/60 Hz

Relay Outputs 91S One process, one malfunction

92S Two process, one malfunction

Relay Ratings Process 10 amp DPDT, gold flash contacts

Malfunction 10 amp SPDT, gold flash contacts

Self-Test Continuous Verifies operation of electronics,

transducer, and crystal bonding

Manual Local or remote push button to

force a malfunction condition

Time Delay Adjustable 0.5–30 seconds on

rising and/or falling level

Fail-Safe Field selectable, high or low level

Repeatability ±0.078" (1.98 mm)

Power Consumption 2.50 VA nominal

Ambient Temperature -40° to +160° F (-40° to +71° C)

Process Temperature -40° to +325° F (-40° to +163° C)

Maximum Pressure 1500 psig @ -40° to +325° F

(103 bar @ -40° to +163° C)

Hot Tap AssembliesAllows installation or removal of Echotel without a process shut-down

11

With a Hot Tap

assembly in

place, an Echotel

switch can be installed

or removed from a pipe

or vessel while the

process remains in

operation. There’s no

need to drain or depres-

surize the tank or shut

down the operation in

order to install or

remove the instrument.

Echotel Hot Tap assem-

blies feature:

• Standard and High

Pressure models

• 316 SS gland

construction

• Carbon steel or

stainless steel

process connections

• Flange and ball valve

optionally available

• 11⁄2" NPT or flange

connection

• Teflon® compression

rings are standard

Standard Hot Tap design(above); high pressuredesign (below).

TRIDENT Electrical Specifications

Trident Current Shift Specifications

Supply Voltage 10-35 VDC

Current Loop Loads 650 ohms with 24 VDC source

1200 ohms with 35 VDC source

Output Process 8 mA (dry) or 16 mA (wet)

Malfunction 5 mA or 19 mA for fault conditions

Self-Test Continuous Verifies operation of electronics,

transducer, and crystal bonding

Manual Local push button to force a

malfunction condition

Time Delay Adjustable 0.5–30 seconds on

rising and/or falling liquid level

Fail-Safe Field selectable, high or low level

Repeatability ±0.078" (1.98 mm)

Power Consumption 1 watt maximum

Ambient Temperature -40° to +160° F (-40° to +71° C)

Process Temperature -40° to +325° F (-40° to +163° C)

Maximum Pressure 1500 psig @ -40° to +325° F

(103 bar @ -40° to +163° C)

Worldwide Level and Flow Solutions SM

®

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Bulletin: 51-170.0 • Effective: July 2002