Position Transducers:

1. Resolver
A resolver is a passive position transducer. It works on the principle of a rotary transformer and consists of one rotor winding and two stator windings located 90' apart. The rotor winding is excited with a voltage Vr. As the shaft rotates, the output voltage of the stator windings varies as the sine and cosine of the shaft angle.

The ratio of the secondary stator voltages:
Note that the angle 0 is no longer a function of the induced absolute Vr, but rather the ratio of Vs I and Vs2. Therefore, variations in the rotor voltage Vr, frequency and temperature are no longer factors in ratiometric output signal Vsl/Vs2. This results in a highly accurate and repeatable resolver decoder.

2. Ultrasonic Linear Transducer
An Ultrasonic Linear Transducer provides a means of accurately measuring linear distance ultrasonically with a minimum of mechanical linkages and extra hardware. There are no moving parts and consequently no wear.

An ultrasonic linear transducer consists of an interface control module, a transducer rod and a "doughnut-shaped" magnet. An electrical interrogation pulse, generated in the interface control module, starts the leading edge of the pulse-width modulation signal. This pulse creates a magnetic field around the conducting element housed inside a magnetorestrictive tube called waveguide. The waveguide, in turn, is enclosed in the nonmagnetic stainless steel tube. The magnetic field from the "doughnut-shaped" permanent magnet, mechanically representative of machine position, reacts with this generated field producing a mechanical force at right angles to the conducting element. This force causes a twist (torsional strain) which slightly twists the waveguide tube. The twist in the tube produces a torsion wave that is transmitted along the waveguide. The time delay from the interrogating pulse until the travelling torsion wave produces a signal in the sensing coil is a direct measurement of the linear position of the "doughnut"magnet. The precise time interval is then converted to digital position inside a linear decoder or a linear PLS.

Magnetic fields normally generated by 60 or 400 Hz equipment will not affect the operation because these frequencies will be rejected by the narrow bandwidth detection used.

Normally, the transducer beam is fixed and the "doughnut" magnet moves with the moving part of the machine. However, the two can be reversed if desired. The relative displacement between the magnet and rod provides the linear position.