AMETEK 955DQ Brik LDT User Manual

Series 956

Series 955

INSTALLATION M

L

INEAR

D

ISPLACEMENT

T

RANSDUCERS

ANUAL

955DQ BRIK

GEN III WITH QUADRATURE OUTPUT

ABSOLUTE PROCESS CONTROL
KNOW WHERE YOU ARE... REGARDLESS

Includes 955DQ

Programming & Maintenance

Instructions Plus Accessory Guide

Preface

This manual is divided into three chapters. Chapter 1
provides the hardware overview for the 955DQ Linear
Displacement Transducers (LDT). Chapter 2 provides
instructions for installing the LDT to a mounting bracket.
Chapter 3 provides an overview and wiring instructions.
To further assist you, a glossary is provided at the back of
the manual.

!

CAUTION
Disconnect Power Before Servicing. The
Gemco 955DQ LDT Contains No Serviceable
Components. Consult Factory for Repair or
Replacement.

AMETEK Automation & Process Technologies has
checked the accuracy of this manual at the time it was
approved for printing. However, this manual may not
provide all possible ways of installing and maintaining
the LDT. Any errors found in this manual or additional
possibilities to the installation and maintenance of
the LDT will be added in subsequent editions. Any
comments you may have for the improvement of this
manual are welcomed.



AMETEK reserves the right to revise and redistribute
the entire contents or selected pages of this manual.
All rights to the contents of this manual are reserved
by AMETEK. The BRIK is a registered trademark of
AMETEK.

2

1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • 248.435.0700 • Fax [phone] • www.AMETEKAPT.com

Table of Contents

Chapter 1 Hardware Overview .......................................4

Chapter 2 Installing the LDT........................................... 6

2.1 Mounting Instructions ............................................................6

2.2 Mounting the Magnet Assembly ...........................................6

Chapter 3 Programming & Maintenance ........................7

3.1 Quadrature Output ................................................................7

3.2 Signal Connection Application Note ......................................7

3.3 Quadrature Output Resolution & Speed................................ 8

3.4 955DQ Wiring Connections...................................................9

3.5 Features ................................................................................16

3.6 955DQ ...................................................................................17

3.7 Troubleshooting for 955DQ ...................................................18

3.8 Catalog Numbering System ..................................................19

3.9 Specifications for 955DQ....................................................... 20

3.10 Accessories ..........................................................................21

Glossary ..........................................................................22

1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • 248.435.0700 • Fax [phone] • www.AMETEKAPT.com

3

Chapter 1 Hardware Overview

Overview

The Series 955DQ BRIK with Quadrature Output is an
accurate, auto-tuning, non-contact, Linear Displacement
Transducer in an economical, low profile package. The
transducer utilizes our field proven magnetostrictive
technology to give absolute position, repeatable to .006%
of the sensing distance. The streamlined anodized
aluminum extrusion houses the sensing element and
electronics. The magnet moves over the sensing
element that determines the position and converts it to
incremental outputs.

Features

The 955DQ has a truly unique feature. This LDT has
auto-tuning capability, the ability to sense a magnet other
than the standard slide magnet and adjust its signal
strength accordingly.

There is an indicator LED that is located at the connector
end of the probe and provides visual status information
regarding the operation of the probe. Green indicates
proper or normal operation. Red indicates the loss of
the magnetic signal or a probe failure. When the probe
is in the normal mode of operation, the LED with remain
illuminated continuously.

encoder input or counter card, eliminating costly absolute
encoder converters and special PLC interface modules.

This model can be ordered with 1 to 9999 cycles per inch
of output resolution. The transducer features an input to
re-zero the probe “on the fly”. Another unique feature is
the “Burst” mode. An input on the transducer triggers a
data transfer of all the incremental position data relative
to the transducer’s absolute zero position. This is how
the incremental output can provide absolute functionality.
The “Burst” input 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 without having to move the machine.

LED Colors

Green Magnet is present and within the active range.

Red Fault, the LDT has lost its signal from the magnet or the

Yellow Used when in the communication/program mode.

magnet has moved into the Null or Dead zone.

Note: The series number on your LDT is a record of all
the specific characteristics that make up your unit. This
includes what interface type it is, its output signal and
range, the type of connector the unit uses, and stroke
length. For a translation of the model number, see
Section 3.8 Catalog Numbering System.

The 955DQ BRIK with Quadrature Output provides an
A quad B digital output signal that is proportional to the
position of the slide magnet assembly along the length
of the probe. The quadrature output makes it possible
to have a direct interface to virtually any incremental

4

1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • 248.435.0700 • Fax [phone] • www.AMETEKAPT.com

Figure 1.1 Dimension Drawing

Accessories

Item Part Number

Slide Magnet SD0521800

Float Magnet SD0522100

Mounting Foot SD0522000

6 Ft. Cable (Option H) SD0527700L6

12 Ft. Cable (Option H) SD0527700L12

25 Ft. Cable (Option H) SD0527700L25

6 Ft. 12 Pin
(Option E Connector)

12 Ft. 12 Pin
(Option E Connector)

Control Arm 955ARMXX (X = Inches)

2.06

1.19

.55

949023L6

949023L12

M5 X .56 DEEP

ALTERNATE MTG.

HOLE FOR LINKAGE

M5 X .40 DEEP

LINKAGE MTG. HOLE

.40

.98

.36

10 PIN MALE

CONNECTOR

A standard female swivel mounting arm is
provided with the slide magnet assembly.
For extensions and other options contact
AMETEK at 800-635-0289.

.22 MTG. HOLES

2 PER MTG. FOOT

.36

.30

1.97

1.372.68

1.80

1.45
.82

.10

Male Connector

.22

SLIDE MAGNET ASSEMBLY
P/N SD0521800

.60

.30

.87

.08

.28

3.00 NULL

R.87

360 ROTATION

Mounting Brackets (SD0522000) slide in the grooves on the
side of the extruded housing. When tightened down with
fastening hardware the mounting bracket clamps the unit into
place. It is recommended to use one mounting bracket on each
end and every three feet between.

R.87

360 ROTATION

1.00

1.50

.56

.25 TO CENTERLINE MAGNET SENSOR

2.00

L = NULL + STROKE + DEAD ZONE

STROKE

FLOATING MAGNET ASSEMBLY
P/N SD0522100

1.31

.34

1.50

DEADZONE

.50

1.00

TO CENTERLINE

OF MAGNET

.34

.75

2.00

1.31

.25



OF MAGNET SLUG



1.30

1.37

1.04

.08

.68

.28

.69

.87

1.50

.56

.25 TO CENTERLINE

OF MAGNET SENSOR

Note: The North Pole of the magnet
should be pointed towards the probe.

1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • 248.435.0700 • Fax [phone] • www.AMETEKAPT.com

.25

.20 THRU

.359 C’BORE
.21 DEEP
OTHER END
2 PLACES

.20 THRU
2 PLACES

.50

5

Chapter 2 Installing the LDT

2.1 Mounting Instructions

The Series 955DQ can be mounted vertically or
horizontally using SD0522000 mounting brackets. The
mounting brackets slide in the grooves on the lower part
of the extrusion and clamp down when tightened. It is
recommended to use one mounting bracket on each end
and every three feet in between.

Ferro-magnetic material, (material readily magnetized)
should be placed no closer than .25” from the sensing
surface of the LDT.

2.2 Mounting the Magnet Assembly

Before mounting the magnet assembly, you should
consider the following

• Ferromagnetic material should not be placed closer
that 0.25” from the LDT’s sensing surface. Failure
to do so could cause erratic operation. Non-ferrous
materials, such as brass, copper, aluminum,
nonmagnetic stainless steel or plastics, can be
in direct contact with the magnet assembly and
sensing surface without producing any adverse
results.

• Make sure that the magnet is located within
the LDT’s active stroke area. Captive magnet
assemblies should be positioned so that they can
move freely over the entire area of the active stroke
without binding or pushing on the extrusion. Non­captive magnet assemblies should be situated so
that the magnet is no further than 3/8” from the
sensing surface at any point in the floating magnet
assembly’s movement.

• When using the Floating Magnet assembly
(SD0522100), the magnet should be installed within
3/8” of the sensing surface. The magnet assembly
should also be installed in such a manner that
it remains an even distance from the aluminum
extrusion throughout the entire stroke. Improperly
installed magnets can result in output signal non-

linearity.

6

1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • 248.435.0700 • Fax [phone] • www.AMETEKAPT.com

Chapter 3 Programming & Maintenance

3.1 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 955DQ 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 specifically for use with a pulsed 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 pulsed 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.

3.2 Signal Connection Application Note

Overview

This application note will clarify the input and output
signals of the 955DQ 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 +24 VDC
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 24 VDC, the threshold voltage would be
approximately 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.

It is important that the customer drive the signal levels
much greater or lower than the threshold voltages.
Asserting a signal with a voltage level close to the
threshold voltage could induce multiple activations of that
input (or none at all) and therefore produce unexpected
results or probe readings.

1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • 248.435.0700 • Fax [phone] • www.AMETEKAPT.com

7

Outputs

The quadrature probe has three outputs, the “A”, “B”
and “Z” outputs. These outputs are “differential” (also
known as “balanced”). That is, the connection for each
output consists of two signal wires. These are typically
described as the “+” and “-” signals. For example, the
“A” channel consists of “A+” and “A-”. The same applies
to the B and Z channels. For these (differential) outputs,
the signal is measured with reference to the other
signal (i.e. the difference or differential). For example;
if the “A+” signal voltage is greater than the “A-” signal,
channel “A” is a logic “1”. Conversely, if the “A+” signal
voltage is lower than the “A-” signal, channel “A” is a
logic “0”. Again, this applies to the B and Z channels as
well. Differential type signals are much less prone to
interference caused by electrical noise or ground loops
more often found in single ended signal connections.

The differential outputs of the A, B and Z channels are
at RS-422 signal levels on option D (output drivers)
units. RS-422 is a well known TIA/EIA standard and
common interface type for incremental encoders. The
RS-422 receiver channel (on the PLC or controller side
of the connection) typically has what is referred to as
a termination resistor connected across the “+” and “-”
signal pins. The value of the termination resistor is (by
RS-422 specifications) typically 100 ohms. However,
some receivers will work with greater resistance values
and some with no termination resistor at all. For proper
signal integrity, especially at higher data rates (i.e.
quadrature pulse frequency), a termination resistor of no
greater than 1K ohm is recommended.

Driving Single Ended Inputs

When using PLS’s or controllers that are not TTL
compatible output driver option “L” should be used.
Option “L” uses a 0L7272 line driver I.C. The output from
this driver will be 1 volt less than the LDT’s input power.

When physically connecting a differential output to a
single ended input, only use the “+” signal, leaving the
“-” signal unconnected. Do NOT connect the “-”
signals to ground. The “A+, “B+” and “Z+” signals
should be connected to their corresponding inputs.
Insulate and tie back the “-” signals. See figure 3-4 or
3-5, Single Ended Interface.

3.3 Quadrature Output
Resolution & Speed

The internal resolution of the 955DQ Gemco LDT is

0.001”. This would be represented to the encoder
input device by specifying an output resolution of 1,000
cycles per inch for the transducer. Although the typical
resolution is 1,000 cycles per inch (CPI), the transducer
can be ordered with virtually any CPI setting.

For a typical rotary type shaft encoder with incremental
quadrature output, the output frequency of the pulses is
governed by the resolution of the encoder (pulses per
turn) and the rotational speed (RPM) of the encoder. The
output pulses rate from the transducer is stretched out
over the LDT internal update time. The output frequency
must be specified so that it does not exceed the
maximum pulse rate of the encoder input card the sensor
is connected to. The output pulse frequency range can
be ordered from 1KHz to 1MHz.

A differential output can also be used to drive single
ended inputs. Special consideration must be given
to these types of applications. It should be noted the
main signal requirements for an RS-422 signal is the
differential voltage of the “+” relative to the “-” signals
and not necessarily the voltage level of any one of these
signals with respect to ground (or common). To meet
the RS-422 specification, this differential voltage only
needs to be +/- 0.2 volts. However, an RS-422 driver
will typically drive either the “+” or “-” signal to around 3.8
volts with respect to ground. This voltage is more than
sufficient to drive TTL level inputs as well as other low
level inputs. The input voltage level specifications of the
PLC or controller being used should be consulted for the
actual level required.

8

1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • 248.435.0700 • Fax [phone] • www.AMETEKAPT.com