Chapter 3: 955Qd Overview; Quadrature Output; Signal Connection Application Note - Ametek Gemco Brik 955QD Series Installation, Programming And Maintenance Manual

With qudrature output, linear displacement transducer

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Chapter 3: 955QD Overview

A new method of interfacing magnetostrictive transducers offers customers an interface as common as analog

with the speed and accuracy of pulsed type signaling. The Gemco 955QD LDT provides quadrature output

directly from the transducer to the controller (see drawing below). The output from the transducer can be

wired directly to any incremental encoder input card, without the need for a special converter module or PLC

interface card designed specically for use with a pulse output magnetostrictive transducer.

The quadrature output provides absolute position data in engineering units. This means that the need for the

calibration constant (wire speed) programming has been removed, thereby eliminating the possibility of having

an improperly calibrated system. The output signal wires are driven by differential line drivers, similar to the

drivers used in most magnetostrictive pulse type transducers, providing a high degree of noise immunity.

A unique feature of this transducer is a "burst" mode of operation. An input on the transducer triggers a

data transfer of all the incremental position data relative to the transducer's absolute zero position. This can

be used to achieve absolute position updates when power is restored to the system or anytime an update

is needed to re-zero or home the machine. Additionally, another input to the transducer can be used to

establish a "zero" position for the transducer.

Overview

This application note will attempt to clarify the input and output signals of the 955QD quadrature probe.

Inputs

The quadrature probe has two inputs, the "zero" and "burst" inputs. These inputs are "single ended". That

is, the connection for each input consists of only one wire, the corresponding signal wire. For these (single

ended) inputs, the signal is measured with reference to the power supply ground, which is sometimes referred

to as "common".

The quadrature probe is available with either +24VDC level signal thresholds or TTL level thresholds. The

signal voltage level required to activate the input for the +24 VDC level signal is proportional to the power

supply voltage that the customer is supplying to the probe. This level is approximately 41% of the power

supply voltage. For example, if the power supply voltage powering the probe is exactly 24VDC, the threshold

voltage would be approximately 9.84 volts.

Installation, Programming and Maintenance Manual

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