Application Guidelines

Over 25 years of experience with ultrasonic gap

switch technology has made the ECHOTEL

brand a world leader in liquid level switches.

Today’slineoffersthreedistinctproductofferings:

• Forapplicationswhereself-testisn’t

required,oureconomical Model 910 with

continuous wave technologyisareliableswitch

withatip-sensitivetransducer.

• Though OEM priced, our compact Models

940/941

offer both advanced tip-sensitive

transducers and pulsed signal technology.

• Single Point Model 961 and Dual Point

Model 962

offer tip-sensitive transducers, pulsed

signal technology, advanced self-test and a time

delay feature.

Models 961/962 represent the pinnacle of

Their continuous self-testing of electronics,

transducer, piezoelectric crystals, and testing

for electromagnetic noise, alarms the user of a

malfunction or the presence of EMI/RFI noise.

An adjustable time delay of 0.5 to 45 seconds helps

curtail nuisance alarms and relay chattering.

With extensive FM, CSA, and ATEX approvals

the Models 961/962 are suitable for virtually any

hazardous location. Their SFF* value of over 90%

makes them suitable for use in Safety Integrity Level

(SIL) 2 loops. Having either relay output or mA current

shift capability, Models 961/962 can be used for more

process applications, making them the most universal

liquid level switches available today.

Advantages and Limitations

The advantages of contact level sensing using

ultrasonic technologies are:

• Low cost single and dual point sensing.

• Accurate and reliable in a wide variety of liquids.

• Unliketuningforks,nodensityadjustmentsrequired.

• Easy installation and simple configuration.

• A broad range of available sensor materials.

• Transmits a stable signal despite liquid property

changes in specific gravity, conductivity, pH, and

dielectric or temperature shifts.

• Switches are 100% electronic and

contain no moving parts which can

degrade or require high 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.

• Liquids which generate crystallized coatings.

• Very aggressive turbulence and splashing.

3

Model

Ultrasonic Technology

Set Points

Output

Mounting

SIL Loop 3-A

Self-Test Time Delay

910

Continuous Wave

Single

Relay

Integral

N.A.

940

Pulsed Signal

Single

Relay

Integral

2

941

Pulsed Signal

Single

Current Shift (CS)

Integral

1

961

Pulsed Signal

Single

Relay or CS

Integral or Remote

2

I

I

I

962

Pulsed Signal

Dual

Relay or CS

Integral or Remote

2

II

At a Glance:

Contact Ultrasonic Switches

25+ Years of Ultrasonic Measurement Solutions for Industrial Process

M

O VING

P

%

ELECTRO

910

*

In the language of Safety Instrumented Systems (SIS), Safe Failure Fraction (SFF) indicates all safe and dangerous detected failures. The

Models 940 and 961/962 SFF values are over 90%, which allows them to be used in SIL

940/941

961