Kaman KD-5100 User Manual

KD-5100

Instruction Manual

Differential Measuring Systems

DO NOT MAKE ANY MODIFICATIONS TO CABLE LENGTH, SENSOR OR

CALIBRATED TARGET MATERIALS WITHOUT PRIOR CONSULTATION WITH

A KAMAN APPLICATION ENGINEER

********

KD-5100 SERIES

DIFFERENTIAL

MEASURING SYSTEM

INSTRUCTION MANUAL

P/N 860029-001 REVISION B

CONTENTS

1. INTRODUCTION............................................................................................. 5

1-1. Calibration...............................................................................................................5

1-2. Maintainability........................................................................................................ 5

1-3. Environments ..........................................................................................................5

2. THEORY OF OPERATION..................................................................... 6

3. OPTIMUM PERFORMANCE.................................................................7

4. APPLICATION INFORMATION.......................................................... 8

5. TARGETS............................................................................................................ 9

5-1. Material ................................................................................................................... 9

5-2. Thickness ..............................................................................................................10

5-3. Size........................................................................................................................ 10

6. SPECIAL HANDLING CAUTIONS................................................. 10

6-1. The Sensors........................................................................................................... 10

6-2. The Mounting Surface ..........................................................................................11

7. FIXTURING....................................................................................................... 12

8. CROSS-AXIS SENSITIVITY................................................................ 15

9. PIN OUT and CONNECTOR ASSIGNEMENTS................... 17

10. USER’S ABBREVIATED FUNCTIONAL TEST.................. 18

11. SENSOR INSTALLATION GUIDELINES AND PROCEDURES

..................................................................................................... 19

12. CALIBRATION............................................................................................ 20

12-1. Pitfalls: ................................................................................................................ 20

12-1a. Dimensional Standard: .................................................................................. 20

12-1b. Recalibration ................................................................................................. 20

12-1c. Thermal Equilibrium..................................................................................... 20

12-2. Equipment Needed to Calibrate:......................................................................... 22

12-3. Calibration Procedure Overview: ....................................................................... 22

12-4. Calibration Steps:................................................................................................ 22

13. TROUBLESHOOTING.......................................................................... 24

14. TERMINOLOGY......................................................................................... 26

TOTAL SYSTEM SPECIFICATIONS*................................................. 28

PERFORMANCE ......................................................................................................... 28

ELECTRICAL ..............................................................................................................28

TEMPERATURE.......................................................................................................... 28

MICRO-CONVERSION SC ALE................................................................ 29

DIGITAL DYNAMIC RANGE........................................................................................ 29

CUSTOMER SERVICE INFORMATION ……………………………30 TECH NOTES…………………………………………………………………….31

ILLUSTRATIONS

Figure 1 Block Diagram: Differential Measuring System .................................................6

Figure 2 Sensor and Target Geometry ................................................................................7

Figure 3 Differential Target Configurations .......................................................................8

Figure 4 x-y Mirror Alignment Configuration.................................................................... 9

Figure 5 Aluminum Targets on Invar.................................................................................. 9

Figure 6 Mounting/Cover Plate Dimensions..................................................................... 11

Figure 7 15N Sensor Dimensions ..................................................................................... 13

Figure 8 20N Sensor Dimensions ..................................................................................... 14

Figure 9 Sensor Coil Dimensions ..................................................................................... 15

Figure 10 Sensor Cable Connections ................................................................................ 17

Figure 11 Power & Output Connections ........................................................................... 17

Figure 12 Sensor Field ......................................................................................................19

Figure 13 Calibration Cover Dimensions ......................................................................... 21

Figure 14 Zero & Gain Control Location Case Dimensions............................................ 23

Figure 15 Null Gap, Offset, Measuring Range .................................................................26

KD-5100 SERIES

DIFFERENTIAL MEASURING SYSTEMS

INSTRUCTION MANUAL

YOUR SYSTEM’S SPECIFICATIONS:

Sensor Type __________ Null Gap __________

Offset __________ Measuring Range __________

Full Scale Output __________ Scale Factor __________

Target Material __________

1. 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.

1-1. 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.

1-2. Maintainability

The KD-5100 is designed so scheduled maintenance and adjustments are not required. The unit can be removed and replaced without special tools.

1-3. Environments

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.

2. THEORY OF OPERATION

2-1. 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.

2-2. 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.

2-3. 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

2-4. 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.

2-5. This differential configuration achieves its high resolution by eliminating the noise and drift any intervening summation and Log amplifiers normally add to the system.

2-6. 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.

2-7. 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. OPTIMUM PERFORMANCE

3-1. To optimize the performance of a KD-5100 system, a high (d) to (s) ration 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

3-2. The 15N sensor used over the specified ±0.009” measuring range provides a d/s ration of

3.08. The ration for the 20N is 10.68. Therefore, if mounting space and target size permit, the 20N offers better performance over the specified measuring range.

3-3. For either sensor model, performance can be improved by decreasing the one variable, the measuring range. Significant reduction can provide a d/s ration up to 35. This effectively lowers the noise floor and improves resolution, linearity, and thermal stability.

3-4. The temperature of the mounting surface and the environment for the electronics should not exceed the specified –20

C to 60oC (-4oF to +140

F). For optimum performance, stabilize the

temperature for the mounting surface/electronics at a constant temperature within this range,

preferably 25

4. APPLICATION INFORMATION

4-1. 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

4-2. 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.

Figure 4 x-y Mirror Alignment Configuration

5. TARGETS

5-1. Material

5-1a. Iron, nickel, and many of their alloys (magnetic targets) are not acceptable for use with the KD-5100.

5-1b. Aluminum is preferred as the most practical target material. You can mount aluminum

targets 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

5-1c. 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.

5-2. Thickness

5-2a. 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.

5-2.b The depth of penetration depends on the actual target material used (Table 1). In cases where the sensors are opposing each other, aluminum target thickness must be at least 0.050” to prevent sensor interaction.

Table 1 Recommended minimum target thickness in mils.

Material Thickness in mils

Silver and Copper 11-13 Gold and Aluminum 13-18 Beryllium 17 Magnesium, Brass, Bronze, Lead 26-39 300 Series Stainless 75 Inconel 95

5-3. Size

The minimum target cross section must be 1½ to 2 times sensor diameter.

6. SPECIAL HANDLING CAUTIONS

6-1. The Sensors

Due to design requirements, the sensor’s most critical component, the coil, is exposed. We ship the sensors 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 it useless.

6-2. The 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 60 dimensions and mounting hole spacing are shown in Figure 6.

C). Base plate

Figure 6 Mounting/Cover Plate Dimensions

7. FIXTURING

7-1. The user provides fixturing for the KD-5100 electronics and sensors. The following information establishes fixturing requirements for optimum system performance. The quality of the measurement is both a function of Kaman’s system and your Fixturing.

7-2. Both the sensor and target fixturing must be structurally sound and repeatable.

7-3. Factors that degrade performance are:

7-3a. Unequal Loading

This refers to an unequal amount of conductive material within the field of one sensor of a pair as opposed to another (the sensor’s field is approximately three times its diameter). Unequal loading causes asymmetrical output from the sensor, which induces nonlinearity in the system output. Ideally, no conductive material other than the target should be in the sensor’s field. Some loading may be acceptable if it is equal and the sensors are calibrated in place. Even then, sensor loading may cause non-linearity. If unable to calibrate – loading is too great.

7-3b. Unequal Displacement

For targets using a pivot point mount (examples, Figures 3 & 4) the system should “see” equal displacement: i.e., the pivot point of the target is perfectly centered between the sensors. If the pivot point is a fraction of a mil off it can introduce non-linearity into the system.

7-4. Other pivot point requirements:

7-4a. The pivot point must be a common line between the centerline of a pair of sensors.

7-4b. The axis of tilt must be a perpendicular bisector of a line between the centerlines of a sensor pair.

7-4c. The pivot point must be positioned on the target so as not to introduce a translation error. This error, a function of angle, is caused by slight changes in the effective null gap as the target moves about the pivot. This results in non-linearity.

7-4d. The pivot point must not change or move with time.

7-5. Sensor mounting considerations:

7-5a. The sensors must be securely clamped. Sensor dimensions are shown in Figures 7 and 8.

Figure 7 15N Sensor Dimensions

+ 28 hidden pages