Kaman KD-5100 User manual

Copyright © 2015 Kaman Precision Products
PART NO: 860029-001 A Division of Kaman Aerospace Corporation
Last Revised: 01/06/15 217 Smith Street
Middletown, CT 06457
www.kamansensors.com
KD-5100
Differential Measuring System
User’s Manual
TABLE OF CONTENTS

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1.0 INTRODUCTION...................................................................................................... 4
2.0 THEORY OF OPERATION...................................................................................... 5
3.0 OPTIMUM PERFORMANCE ................................................................................... 6
4.0 APPLICATION INFORMATION............................................................................... 7
5.0 TARGETS................................................................................................................ 8
5.1 Material................................................................................................................. 8 
5.2 Thickness ............................................................................................................. 9
5.3 Size....................................................................................................................... 9
6.0 SPECIAL HANDLING CAUTIONS.......................................................................... 9
6.1 Sensors ................................................................................................................ 9
6.2 Mounting Surface................................................................................................ 10
7.0 FIXTURING............................................................................................................ 11
7.1 Factors that degrade performance:...................................................................... 11
7.2 Pivot point requirements: ..................................................................................... 11
7.3 Sensor mounting considerations:......................................................................... 13
8.0 CROSS-AXIS SENSITIVITY.................................................................................. 14
8.1 Cross-axis sensitivity may occur under the following conditions:......................... 14
8.2 Additional points of emphasis about cross-axis sensitivity:.................................. 14
9.0 PIN OUT and CONNECTOR ASSIGNMENTS...................................................... 15
10.0 USER’S ABBREVIATED FUNCTIONAL TEST................................................... 16
11.0 SENSOR INSTALLATION GUIDELINES AND PROCEDURE............................. 17
11.1 Guidelines.......................................................................................................... 17
11.2 Procedure .......................................................................................................... 17
12.0 CALIBRATION..................................................................................................... 19
12.1 Equipment Required .......................................................................................... 20
12.2 Calibration Procedure Overview ........................................................................ 20
12.3 Calibration Steps ............................................................................................... 21
13.0 TROUBLESHOOTING......................................................................................... 23
14.0 TERMINOLOGY................................................................................................... 24
15.0 CUSTOMER SERVICE INFORMATION.............................................................. 25
APPENDIX A: Total System Specifications*(sensor, cable, and electronics) .............. 26
APPENDIX B: Measuring Range and Performance Tradeoffs .................................... 27
APPENDIX C: Output Filter Characteristics of the KD-5100........................................ 35

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ILLUSTRATIONS
Figure 1 Block Diagram: Differential Measuring System ............................................... 5
Figure 2 Sensor and Target Geometry........................................................................... 6
Figure 3 Differential Target Configurations..................................................................... 7
Figure 4 x-y Mirror Alignment Configuration................................................................... 8
Figure 5 Aluminum Targets on Invar .............................................................................. 8
Figure 6 Mounting/Cover Plate Dimensions ................................................................. 10
Figure 7 15N Sensor Dimensions ................................................................................ 12
Figure 8 20N Sensor Dimensions ............................................................................... 12
Figure 9 Sensor Coil Dimensions................................................................................. 13
Figure 10 Sensor Cable Connections........................................................................... 15
Figure 11 Power & Output Connections ....................................................................... 15
Figure 12 Sensor Field ................................................................................................. 17
Figure 13 Calibration Cover Dimensions...................................................................... 20
Figure 14 Zero & Gain Control Location Case Dimensions.......................................... 21
Figure 15 Null Gap, Offset, Measuring Range ............................................................. 24

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KD-5100 SERIES
DIFFERENTIAL MEASURING SYSTEMS
SYSTEM SPECIFICATIONS:
Sensor Type __________ Null Gap __________
Offset __________ Measuring Range __________
Full Scale Output __________ Scale Factor __________
Target Material __________
1.0 INTRODUCTION
This manual describes installation and use of the KD-5100, theory of operation, ways to
optimize performance, special handling cautions, functional tests, and guidelines for fixturing
and targets, and calibration procedures.
Calibration
Though there is a section on calibration, these systems are shipped from the factory calibrated
for a user specified target, sensitivity, and measuring range. We calibrate these systems in a
controlled environment using a precision laser as a primary dimensional standard. Since it is
difficult for users to duplicate our calibration conditions, call us before attempting any
adjustments of your KD-5100. On the other hand, it is equally difficult for Kaman to duplicate
your actual application conditions, so special circumstances may dictate come calibration.
Again, coordinate with a Kaman engineer first.
Maintainability
The KD-5100 is designed so that scheduled maintenance and adjustments are not required.
The unit can be removed and replaced without special tools.
Environment
The KD-5100 provides specified performance after exposure to all natural and/or induced
environments encountered during manufacture, test, transportation, handling, storage,
installation, and removal operations.

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2.0 THEORY OF OPERATION
The KD-5100 Differential Measuring System uses advanced inductive measurement technology
to detect the aligned or centered position of a conductive target. Two matched sensors are
positioned relative to the target so that as it moves away from one sensor it moves toward the
other an equal amount.
The transducer operates on the principle of impedance variation caused by eddy currents
induced in a conductive target located within range of each sensor. The coil in the sensor is
energized with an AC current, causing a magnetic coupling between the sensor coil and the
target. The strength of this coupling depends upon the gap between them and changes in gap
cause an impedance variation in the coil.
In the KD-5100, the coils of a pair of sensors form the opposite legs of a balanced bridge circuit
(Figure 1).
VOLTAGE
REGULATOR
+15 Vdc
COMMON
-15 Vdc
Figure 1 Block Diagram: Differential Measuring System
When the target is electrically centered between the two sensors at the nominal null gap for
each, the system output is zero. As the target moves away from one sensor and toward
another, the coupling between each sensor and target is no longer equal causing an impedance
imbalance between the sensors. The bridge detects this imbalance and its output is amplified,
demodulated, and presented as a linear analog signal directly proportional to the targets
position. This is a bipolar signal that provides both magnitude and direction of misalignment.
Only the differential output is available.

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This differential configuration achieves its high resolution by eliminating the noise and drift any
intervening summation and Log amplifiers normally add to the system.
Maximum performance depends upon advanced sensor technology. Factors critical to the high
resolution of the KD-5100 are tighter manufacturing control, using significantly larger coils for a
given range of operation, and electrically matching the sensors.
By using electrically matched sensors on opposing legs of the same bridge, temperature effects
common to the sensors and cabling of a differential sensor pair tend to be cancelled. This is
true for the mechanical aspects of the sensor/target system also. Assuming the thermal
characteristics of each sensor track together, slight changes in sensor length due to
temperature tend to be cancelled.
3.0 OPTIMUM PERFORMANCE
To optimize the performance of a KD-5100 system, a high (d) to (s) ratio is desired: (d) is the
sensor coil diameter and (s) includes: the null gap, the positive measuring range, and ½ of the
coil depth (Figure 2).
Figure 2 Sensor and Target Geometry

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The 15N sensor used over the specified ±0.009” measuring range provides a d/s ratio of 3.08.
The ratio for the 20N is 10.68. Therefore, if mounting space and target size permit, the 20N
offers better performance over the specified measuring range.
For either sensor model, performance can be improved by decreasing the one variable, the
measuring range. Significant reduction can provide a d/s ratio up to 35. This effectively lowers
the noise floor and improves resolution, linearity, and thermal stability.
The temperature of the mounting surface and the environment for the electronics should not
exceed the specified –20oC to 60oC (-4oF to +140oF). For optimum performance, stabilize the
temperature for the mounting surface/electronics at a constant temperature within this range,
preferably 25oC.
4.0 APPLICATION INFORMATION
For differential measurement applications, the two electronically matched sensors are
positioned on opposite sides or ends of the target (Figure 3). The sensor to target relationship
is such that as the target moves away from one sensor, it moves toward the other an equal
amount.
Figure 3 Differential Target Configurations
A standard system comes with two measurement axes (four sensors – two per axis) and can
therefore be fixtured a number of ways to provide precise x-y alignment. Figure 4 illustrates
target configuration for x-y alignment of an image stabilization mirror for an electro-optical
application.
DO NOT MAKE ANY MODIFICATIONS TO CABLE LENGTH, SENSOR OR
CALIBRATED TARGET MATERIALS WITHOUT CONSULTATING A
KAMAN APPLICATION ENGINEER

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Figure 4 x-y Mirror Alignment Configuration
5.0 TARGETS
5.1 Material
Iron, nickel, and many of their alloys (magnetic targets) are not acceptable for use with the KD-
5100.
Aluminum is preferred as the most practical target material. Aluminum targets can be mounted
on materials with more stable temperature characteristics such as Invar or other substrates as
long as target thickness guidelines are observed (Figure 5).
Figure 5 Aluminum Targets on Invar
These systems are set up to work with other nonmagnetic conductive targets on a special order
basis. If you purchased a system for use with a target material other than aluminum, it has
been calibrated (with selected component values) at the factory using that target material. An
arbitrary change in target material may, at a minimum, require calibration or, not work at all.

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5.2 Thickness
The RF field developed by the sensor is at a maximum on the target surface. There is
penetration below the surface and the extent of penetration is a function of target resistivity and
permeability. The RF field will penetrate aluminum to a depth of 0.022”, a little more than three
“skin depths” (at one skin depth the field density is only 36% of surface density and at two skin
depths it is 13%). To avoid variations caused by temperature changes of the target, the
minimum thickness should be at least three skin depths.
The depth of penetration depends on the actual target material used. In cases where the
sensors are opposing each other, aluminum target thickness must be at least 0.050” to prevent
sensor interaction.
Material Thickness in mils
Silver and Copper 22
Gold and Aluminum 22
Beryllium 25
Magnesium, Brass, Bronze, Lead 58
300 Series Stainless 110
Inconel 110
Recommended minimum target thickness in mils.
5.3 Size
The minimum target size is at least 2 times sensor diameter.
6.0 SPECIAL HANDLING CAUTIONS
6.1 Sensors
Due to design requirements, the sensor coil is exposed. The sensors are shipped with
protective caps. Keep them in place until installation of the sensors.
CAUTION: If any sharp object comes in contact with the coil face or edge and damages it in
any way, this could short a number of turns in the coil, alter its impedance, and render the
sensor useless.

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6.2 Mounting Surface
The base plate of the electronics module has a smooth surface to enhance thermal conduction
away from the electronics. Mounting the base plate flush with another surface will enhance
thermal dissipation (assuming a mount surface with a temperature below 60oC). Base plate
dimensions and mounting hole spacing are shown in Figure 6.
Figure 6 Mounting/Cover Plate Dimensions