TRANSDUCER MOUNTING

5

CAUTION: Please read the entire installation section carefully prior to starting installation. Also read the Measurement

Range Calculations section on pages 3-4 to make sure that you have selected the proper level system for your application.

CAUTION: If equipment is used in a manner not specified by manufacturer, protection provided by equipment may be impaired.

GENERAL GUIDELINES

The unit can be provided as an integral mount Model 300

with the transducer connected to the transmitter housing, or

as a remote mount Model 301 with the transmitter mounted

as far as 500' (152 m) away from the transducer. Both the

transducer and the transmitter are approved for Class

I,

Division 1, Groups B, C, & D areas.

TRANSDUCER MOUNTING LOCATION

Proper mounting of the ultrasonic transducer is very critical

to the operation of any non-contact ultrasonic application.

Both the accuracy and the reliability of the Model 300/301

can be adversely affected if the transducer is mounted

improperly. This section must be followed carefully to make

sure that the optimum mounting location is chosen, and that

proper mounting techniques are used for the transducer.

Several factors should be considered when selecting the

transducer location:

• Inherent dead band of the transducer

• Standpipes

• Application difficulties (foam, turbulence, vapors)

• Ultrasonic beam angle

TRANSDUCER DEAD BAND

The transducer must be mounted directly over the liquid sur-

face, as shown in Figure 1. Non-contact ultrasonic instru-

ments require a “dead band” or “blind space” between the

face of the transducer and the maximum liquid level. The

minimum dead band for the Model 300/301 is 18" (457 mm).

This dead band should be taken into consideration when

mounting the transducer. If the level must be measured all

the way to the top of the tank, the transducer should be

mounted in a standpipe as shown in Figures 2 and 3.

STANDPIPES

In applications where the material level may come into the

dead band, the transducer must be mounted in a standpipe.

The diameter of the standpipe should be at least 8" (203

mm); and its length should be limited to 11" (279 mm) from

transducer face. Refer to Figure 2.

APPLICATION DIFFICULTIES

Typically the liquid surface is most turbulent at the fill point.

Foam on the other hand, is most likely to accumulate at the

opposite end of the fill. Since foam and turbulence can both

create difficulties in reflecting a strong ultrasonic signal back

into the transducer, it is best to pick a mounting location

away from these areas in the vessel.

Avoid installing the transducer in tank top openings that

exhaust heated air or vapors. The boundaries between the

vapors and the outside air often represent acoustic imped-

ance gradients that can cause troublesome sound reflec-

tions. In those installations, the transducer should be mount-

ed well away from the opening inside the tank, or in a stand-

pipe as illustrated in Figures 2 and 3.

Model 300

Air

Liquid

Dead band

18" minimum

(457 mm)

Flange

Maximum span

28.5' (8.7 m)

Figure 1

Typical Transducer Mounting

8" (203)

Minimum I.D.

2" NPT

Transducer

This end welded

or flanged

Stand

pipe

Maximum 11"

(279 mm) or less

Figure 2

Transducer Mounting in Standpipe

Figure 3

Transducer Mounting for Tanks with Exhaust