Specifications

A-17

800-TEC-ENGR

www.avg.net

Position Transducers/Sensors

SECTION

Principle of Operation

An ultrasonic linear transducer consists of an interface control

module, a nonmagnetic stainless steel rod with sensing head

and a "doughnut" magnet. An electrical interrogating pulse,

generated in the interface control module, creates a magnetic

field around the conducting element housed inside a wave-

guide which in turn is enclosed in the nonmagnetic stainless

steel transducer rod. The "doughnut-shaped" permanent mag-

net, mechanically representative of machine position, reacts

with this generated field producing a mechanical force at right

angle to the conducting element. This force causes a twist (tor-

sional strain) which travels back the length of the rod. These

strain pulses arrive at a fixed reference a certain time interval

later and this time delay from the interrogating pulse indicates

the linear position of the "doughnut" magnet. These precise

time-based pulses are then converted to digital output inside a

linear decoder or a linear PLS.

Magnetic fields normally generated by 60 or 400 Hz equip-

ment will not affect the operation because these frequencies

will be rejected by the narrow bandwidth detector used.

Normally the transducer rod is fixed and the "doughnut" mag-

net moves with the moving part of the machine. However, this

can be reversed if desired. The relative displacement between

the two parts provides the output signal.

LT140

LT140 LINEAR ULTRASONIC POSITION

TRANSDUCER

ABSOLUTE POSITION TRANSDUCER

◆ Absolute linear position

◆ Ultrasonic position sensing; no moving parts

◆ Easy to install

◆ Accurate to 0.001" (0.025 mm)