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 ******** Copyright © 2000 PART NO: 860029-001 Rev.
KD-5100 SERIES DIFFERENTIAL MEASURING SYSTEM INSTRUCTION MANUAL P/N 860029-001 REVISION B 2
CONTENTS 1. INTRODUCTION............................................................................................. 5 1-1. Calibration............................................................................................................... 5 1-2. Maintainability........................................................................................................ 5 1-3. Environments .......................................................................................................... 5 2.
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.......
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.
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.
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.
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 –20oC to 60oC (-4oF to +140oF).
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.
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%).
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 60oC). Base plate dimensions and mounting hole spacing are shown in Figure 6.
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.
Figure 7 15N Sensor Dimensions 13
Figure 8 20N Sensor Dimensions 7-5b. The target must not strike the sensor face. This system has a null gap of 15 mils (0.015”/0.381mm) for the 15N sensor and 20 mils (0.020”/0.508mm) for the 20N sensor. The specified full measuring range for both sensors is ±0.009” (±0.228mm). The difference between the null gap and measuring range (6 mils for the 15N and 11 mils for the 20N) is the offset distance for the sensors.
N 20N Figure 9 Sensor Coil Dimensions 7.5d. If the face of the sensor and the target surface are not parallel (if the sensor centerline is not perpendicular to the target) more than 2o to 3o, it will introduce error to the measurement. 8. CROSS-AXIS SENSITIVITY 8-1. Assuming you have stable and repeatable fixturing, and have followed all of the rules for target mounting, pivot points, etc., under certain conditions the system may exhibit signs of error we classify as cross-axis sensitivity. 8-2.
8-3b. The degree of error is related to the angle between the sensor and target face. As a general rule, for angles ± 1o or less, there is virtually no problem with cross-axis sensitivity. Sensor/target angle is a function of the distance between the sensor and target pivot, and the measuring range. A sensor with a range of ± 10 mils mounted 10 mils from the pivot will experience 45o of tilt at the end points. This is an extreme example but suffices to illustrate the point.
9. PIN OUT and CONNECTOR ASSIGNEMENTS 9-1. Sensor cable connections (Figure 10): AXIS 1 2 CONNECTORS J3 J1 J4 J2 SENSORS S3 S1 S4 S2 Figure 10 Sensor Cable Connections 9-2. Pin assignments for the Power/Signal line connector J5 (Figure 11): PIN 1 2 3 4 5 6 7 8 9 FUNCTION + 15Vdc* - 15 Vdc* Power Supply Common Signal Output: Axis 1 Return Signal for Pin 4 Signal Output: Axis 2 Return Signal for Pin 6 Not Used Not Used *Power Requirements + 15Vdc - 15 Vdc Tolerance +1.0, -0.5Vdc +0.5, -1.
10. USER’S ABBREVIATED FUNCTIONAL TEST NOTE: This is not a calibration or installation procedure. This unit is factory calibrated, and installation guidelines are in the next section. This is simply a check to make sure your system is functioning upon receipt. 10-1. Procedures Perform this abbreviated functional test prior to installation of the electronics and sensors in the application fixture. 10-1a. Attach the power supply cable to connector J5 and apply power to the system. 10-1b.
11. SENSOR INSTALLATION GUIDELINES AND PROCEDURES 11-1. The electrical nulling procedure. Note: This installation procedure is the preferred method. Though both sensors may be positioned mechanically, this can cause a cumulative error. By electrically positioning the second sensor of a pair using system output, any existing error is self-canceling. 11-2. Install the sensors so that only the target interacts with the sensor’s field.
until the system output reads 0Vdc (ideally, 0.000 volts). This output means the sensor is positioned correctly. 11-5. Repeat steps 11-3 and 11-4 for sensor S4 and S2. 11-6. The system is now ready to use. 12. CALIBRATION 12-a. These systems are shipped from the factory pre-calibrated for a user specified measuring range, sensitivity, and target material. They do not normally require calibration or re-calibration. Yet some applications dictate the availability of this option. 12-b.
the cover plate for heat sinking. The calibration controls are located inside the unit and the cover plate must be removed to access them. Removing the cover plate removes its heat sinking function. Calibrating with the cover off and then reinstalling it will cause enough of a thermal gradient to throw the calibration off. 12-1c1. Kaman’s solution is to use a cover plate with holes drilled in it for access to the calibration controls. This plate is available as an accessory from Kaman.
12-2. Equipment Needed to Calibrate: 1. 2. 3. 4. 5. A dimensional standard A regulated ± 15 Vdc power supply A voltmeter accurate to one millivolt An insulated adjusting tool (“tweaker”) Kaman P/N 823977-T007 A calibration cover plate NOTE: When you do a system calibration, if at all possible, do it with the system installed in the application fixture at normal operating temperatures.
12-4d. To adjust for 0.000 volts: 1) Monitor the output of axis 1. 2) Using the adjusting tool, adjust the zero control for axis 1 (Figure 13) for 0.000 volts output. Figure 14 Zero & Gain Control Location Case Dimensions 12-4e. Move the target through a known displacement to its maximum range (9 mils standard) and adjust the axis 1 gain control (Figure 14) for the desired output (9 volts standard). 12-4f. Return the target to the null position and check the output. You most likely will not see 0.
13. TROUBLESHOOTING 13-a. What if the above calibration process doesn’t work, if there is not enough gain for the desired output, or if you cannot get a consistent 0V±10mV? 13-1. Insufficient Gain 13-1a. To repeat, if attempting to recalibrate for a sensitivity, measuring range, or target different from factory calibration specifications, there may be insufficient gain control.
and it passed the Abbreviated Function Test, it is the least likely candidate as the source of the problem.
14. TERMINOLOGY NULL GAP The null gap is the point at which a target is equidistant from each sensor of a differential pair. The system output at null = 0Vdc. The actual gap is measured from the sensor face to the corresponding target face and includes a required offset (null gap = offset plus maximum measuring range). OFFSET The offset is the minimum distance between the sensor face and the target.
LINEARITY Linearity is the maximum deviation of any point of a calibrated system’s output from a best-fit straight line. Express in actual units, e.g., microinches. EQUIVALENT RMS INPUT NOISE Equivalent RMS Input Noise is a figure of merit used to quantify the noise contributed by a system component. It incorporates into a single value, several factors that influence a noise specification such as signal-to-noise ration, noise floor, and system bandwidth.
TOTAL SYSTEM SPECIFICATIONS* (sensor, cable, and electronics) PERFORMANCE (typical for stated measurement conditions) English (inches) Metric (mm) Null Gap KD-5100-15N KD-5100-20N 0.015±0.0001 0.020±0.0001 0.381±0.003 0.508±0.003 Measuring Range KD-5100-15N KD-5100-20N ±0.009 ±0.009 ±0.2286 ±0.2286 Sensitivity or scale factor 1V/0.001±2% 40mV/0.001±2% Non-Linearity KD-5100-15N KD-5100-20N ±2 x 10-5 ±1 x 20-5 ±0.5 x 10-3 ±2.
MICRO-CONVERSION SCALE ENGLISH TO METRIC CONVERSIONS (0.001” = 1 mil = 25.4 mm) inch mil micro-inch nano-inch meter mm micro-meter nanometer Angstrom 1.0000E+00 1.0000E-03 1.0000E-06 1.0000E-09 1.0000E+03 1.0000E+00 1.0000E-03 1.0000E-06 1.0000E+06 1.0000E+03 1.0000E+00 1.0000E-03 1.000E+09 1.000E+06 1.000E+03 1.000E+00 2.5400E-02 2.5400E-05 2.5400E-08 2.5400E-11 2.5400E+01 2.5400E-02 2.5400E-05 2.5400E-08 2.5400E+04 2.5400E+01 2.5400E-02 2.5400E-05 2.5400E+07 2.5400E+04 2.5400E+01 2.
Customer Service Information Should you have any questions regarding this product, please contact an applications engineer at Kaman Instrumentation Operations 719-635-6979 or fax 719-634-8093. You may also contact us through our web site at www.kamaninstrumentation.com.
NONCONTACT POSITION MEASURING SYSTEMS KD5100 KD5100 Measuring Range and Performance Tradeoffs The question is often asked what the limitations on the range of the KD5100 are. This question is typically answered with the question “What performance is required in the application”? This tech note will present the performance tradeoffs associated with range on the KD5100 differential measurement system.
Non-Linearity Non-linearity is computed as the maximum error from a best fit (least squares) line and divided by the full range. A system with a non-linearity of ±0.2%FR and a ±10 mil (±0.25mm) range (20 mil (0.5mm) Full Range) would have a maximum deviation of 0.2%x20mil=0.04mils (0.2%x0.5mm=0.001mm). Best Fit Non-Linearity as % of Full Range Estimated Non-Linearity of KD5100 6.00% 5.00% 4.00% 3.00% 2.00% 1.00% 0.
Temperature Coefficient Temperature coefficient is calculated as the worst case shift over temperature. Temperature coefficient is also presented as a percentage of Full Range. A system with a full range of 20 mils (0.5mm) would have system with a temperature coefficient of ±0.02%FR/oC or about 0.004mils/oC (0.1µm/oC). Typically the temperature coefficient of a KD5100 is the worst when at the extremes of the range and is excellent at the null position because the sensors are balanced.
Relative Sensitivity The relative sensitivity is a way of comparing the expected resolution of the system. The relative sensitivity is computed such that a system with a relative sensitivity of 1 would have resolution of 0.005%FR peak-to-peak when measured at a 1kHz bandwidth with the sensors positioned at the extreme end of the measuring range. The resolution at null is generally better by a factor of 3. A relative sensitivity of 0.
Specific Example: 15N Sensors The estimates below are for a 15N sensor. The estimates are based on the coil diameter of 143 mils (3.63mm). The two tables contain the same data, just in different units. Note there is an entry for a 2 mil range (+/-1mil) (~50 micron -- +/-25micron). This entry is based on a considerable amount of experience with this system and was not calculated. KD5100-15N Sensor -- English Units %Coil Offset, Range Null, Range NL, NL,mil Sensor Sensor Relative FR Res, Dia.
Specific Example: 20N Sensors The estimates below are for a 20N sensor. The estimates are based on the coil diameter of 363 mils (9.22mm). The two tables contain the same data, just in different units. KD5100-20N Sensor -- English Units %Coil Offset, Range Null, Range NL, NL,mil Sensor Sensor Relative FR Res, Dia. mil ,mil (+/-) %FR TC, TC, Sens.
Application Variables and Caveats There are some application variables that will also affect performance. The effects listed are not considered in the results of this tech note. These effects must be considered separately. Sensor Loading: Sensor loading by conductive materials that are incidentally in “view” of the sensors can affect the results significantly and must be considered on a case-by-case basis. The discussions in this tech note assume that incidental materials do not load the sensor.
Method of Computing Performance These results are based mainly on simulations. First the sensor inductance and resistance was computed using a modeling program. Then the effect of 2 meters of cable was factored in taking in consideration the transmission line effects of the cable. After that the resultant inductance and resistance was put in a model to simulate the circuit bridge network. The performance in each case was optimized to provide temperature coefficient as close to .
NONCONTACT POSITION MEASURING SYSTEMS KD5100 Output Filter Characteristics of the KD5100 Applications utilizing the KD5100 as the displacement feedback in closed loop systems generally require information about the gain and phase delay vs. frequency. The output filter largely controls these KD5100 characteristics in most applications. Output Filter Schematic The output filter is a standard 2 pole butterworth configuration. It is set for a cutoff frequency (3dB) of approximately 23 kHz.
Analysis Results The filter was analyzed using Micro-Cap V. The plot and table below show the magnitude (dB) and phase (degrees) output for the standard configuration in the KD5100. The –3dB point is at about 23kHz. There is a small gain of 1.59 (about +4dB) in the circuit. ) of approximately 23 kHz. Figure 1 – Output Filter Schematic Analysis Results The filter was analyzed using Micro-Cap V.
Figure 2 – Analysis Results of Magnitude and Phase Vs. Frequency Frequency, Hz Magnitude, dB 10 100 1000 2000 5000 10000 20000 23600 +4.03 dB +4.03 dB +4.03 dB +4.03 dB +4.02 dB +3.74 dB +2.17 dB +0.94 dB Relative Magnitude, dB 0.00 0.00 0.00 0.00 -0.01 -0.29 -1.86 -3.09 Phase Shift, degrees 0.00 -0.36 -3.50 -7.01 -18.72 -38.8 -78.50 -91.
