User guide

16
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4.1: Quadrature Output
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 952 QD Linear
Transducer 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 RS-422 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.
4.2: Signal Connection
Application Note
Overview
This application note will attempt to clarify the type
of signals coming out of and going into the 952QD
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 also
sometimes referred to as common.
The quadrature probe is available with either +24
VDC level signal thresholds or TTL level thresholds.
The signal voltage level required to activate the
input for the +24 VDC level signals 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 +24 VDC, the threshold voltage would be
about 9.84 volts.
The TTL level threshold signals are activated when
these inputs exceed the typical TTL level threshold,
which is 2.0 VDC.
Additionally, for the +24 VDC level signals, the
customer can specify either a sourcing or sinking
type of input. A sourcing input type is pulled high
internal to the probe. To activate a sourcing input,
the customer must pull the signal lower than the
threshold voltage to activate the input. A sourcing
input is usually driven by a sinking output or a
switch connected to ground. A sinking input type is
pulled low internal to the probe. To activate a sinking
input, the customer must pull the signal higher than
the threshold voltage to activate the input. A sinking
input is usually driven by a sourcing output or a
switch connected to the power supply.
Chapter 4: 952 QD Overview