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KDM-8206 Non-Contact Displacement Measuring System User’s Manual This apparatus, when installed and operated per the manufacturer’s recommendations, conforms with the protection requirements of EC Council Directive 89/336/EEC on the approximation of the laws of the member states relating to Electromagnetic Compatibility. Refer to the KMD-8206 Declaration of Conformity or contact Kaman Measuring Systems for details.
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Table of Contents PART 1 – KDM-8206 DESCRIPTION.................................................................................................... 3 PART 2 – CONNECTING THE KDM-8206............................................................................................ 5 PART 3 – KDM-8206 OUTPUTS ........................................................................................................... 7 3.1 ANALOG VOLTAGE OUTPUT: ........................................................................
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PART 1 – KDM-8206 DESCRIPTION Kaman Precision Products’ Model KDM-8206 is a non-contact, linear, analog displacement measuring system. The system operates on a traditional inductive bridge circuit. This easy-to-use, versatile system can be utilized for precision static and dynamic measurements of conductive targets. The sensor coil makes up one or two legs (depending on single or dual coil sensor) of a balanced bridge network.
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A KDM-8206 Measuring System consists of multiple Measuring Channels installed in a rack enclosure. The rack typically includes a 110/220 VAC, 50/60 Hz power supply and may also contain a digital display. Kaman Precision Products www.kamansensors.
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PART 2 – CONNECTING THE KDM-8206 All input, output, and synchronization connections to the KDM-8206 Measuring Module are at the terminals of the Euro connector on the rear of the enclosure. The Measuring Module is designed for insertion in a 3U/84HP rack enclosure. The rack provides a mating Euro connector and input power supply. The sensor input is via a TBNC connector on the rear panel of the rack. The output signal is a BNC coaxial connector also on the real panel.
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All connections in the table are present in a Kaman supplied rack enclosure; no additional wiring must be specified. Some comments on the connections in this table are as follows: 1. NC = Not Connected 2. Single channel voltage output is between pins A/C 14 and Ground. This is connected to the upper BNC connector on rear panel of the rack. 3. Differential voltage output is between pins A/C 14 (V+Out) and A/C 16 (V-Out). Output at pins A/C 16 is not present unless enabled on the Measuring Channel PCB.
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PART 3 – KDM-8206 OUTPUTS The KDM-8206 Measuring Channel has a variety of analog outputs. Standard outputs are: Vout (single ended voltage) Iout (4-20 mA current). Optional outputs are: Low voltage (0-1, 0-2) Differential (balanced) voltage Demodulator output Reverse current (20-4 mA) Modifications to the Measuring Module and/or Rack may be required for the optional outputs. Single ended voltage calibration is provided unless otherwise specified.
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A special calibration record of this output can be provided upon request. No attempt is made to linearize or otherwise adjust demodulator output for the calibration record; it is a record of the output only. 3.4 Differential (Balanced) Output: For industrial applications, high noise environments or long output cable lengths, an optional differential output is available.
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PART 4 – CALIBRATING THE KDM-8206 Figure 4 Front View of KDM-8206 Measuring Module 4.1 Calibration Controls There are 6 controls to calibrate the KDM-8206, all located on the front panel and accessible by the narrow end of an adjustment tool. The controls are: Coarse & Fine MIN, Coarse & Fine MID, Coarse & Fine MAX. The terms MIN, MID, and MAX refer to which part of the measuring range that the control is intended to adjust. Coarse controls give a large change in output and are always adjusted first.
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ZERO AFTER CONTROL ADJUSTMENT TARGET DISPLACEMENT -OUTPUT +OUTPUT ZERO INITIAL CALIBRATION After calibration, the MIN controls can be used to shift system output anywhere from 40-60% below the x-axis, depending on sensor, sensor mounting and gain. This feature is useful in applications where a ± deviation from a standard or a bipolar output is required. The MIN controls can be utilized for final positioning of the output after installing the sensor in it a mechanical fixture.
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4.2 Calibration Methods The KDM-8206 has three possible calibration methods. The current output can only be calibrated for 4 to 20 mA, so there is no possible bipolar calibration. Full Scale: (Voltage Out) Output from 0 VDC to some maximum value. (Current Out) Output from 4 mA to 20 mA Bipolar: Negative output for first half of range; positive output for second half. High Accuracy Band: Increased linearity by using only part of the full-scale Measuring range (Voltage or Current).
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4.3 Calibration Procedures Here are some general comments that are applicable to all calibration procedures: 1. Mechanical positioning of the sensor must be performed accurately using a calibrated micrometer fixture, precision spacers, or other dimensional standard. 2. A sample of the actual material to be measured by the system must be used as a calibration target. Conductivity of the measured material affects system performance. 3.
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6. Reposition the target to full-scale displacement, plus offset. Read the output voltage and note the difference between the actual reading and the desired reading. Adjust the MAX controls until the output reads the desired voltage level, then continue past the desired reading by an amount equal to the first difference you noted. This technique is called 100% oversetting and is used to reduce the number of iterations needed to calibrate the system. For example, if the output reads 9.
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With the 250 ohm load and current meter connected as in FIGURE 4, verify the calibration. Some adjustment of the front panel controls may be necessary to “fine tune” the current output. 1. Position the target to minimum displacement (i.e. offset). Adjust the MIN controls until the output is 4 mA. 2. Reposition the target to mid-scale. Adjust the MID controls until the output voltage reads 12 mA. 3. Reposition the target to full-scale displacement. Adjust the MAX controls until the output reads 20 mA. 4.
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6. Reposition the target to full-scale displacement, plus offset. Read the output voltage and note the difference between the actual reading and the desired reading. Adjust the MAX controls until the output reads the desired voltage level, then continue past the desired reading by an amount equal to the first difference you noted. This technique is called 100% oversetting and is used to reduce the number of iterations needed to calibrate the system. 7.
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VDC 4.3.5 High Accuracy Band Voltage Calibration High Accuracy Band Calibration offset CALIBRATED RANGE 0 DISPLACEMENT This procedure is used to monitor changes in position that are less than the specified linear measuring range of the sensor, or for increased accuracy over a smaller range when not concerned about high accuracy outside of that range. The high accuracy band procedure maximizes the linearity of output within a calibrated span.
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PART 5 – SYNCHRONIZING MULTIPLE MEASURING CHANNELS When sensors are used in close proximity to one another, performance will be compromised unless the Measuring Channels are synchronized. Performance degradation is due to interaction of the sensor fields and is likely to appear as a low frequency oscillation on the output signal. In general, sensors located adjacent to each other with less than 3x sensor diameter spacing will require synchronization.
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PART 6 – SYSTEM MODIFICATIONS 6.1 Temperature Compensation While inductive sensors offer advantages over competing technologies, one of the limitations of this technology is thermal error due to varying temperature at the sensor location. The effect of temperature changes can be minimized, but not totally eliminated. These thermal errors appear in two forms: 1. Thermal Zero Shift – a change in where the output voltage intersects zero on the output curve.
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6.4 Bridge Card The KDM-8206 Measuring Module is stocked in two basic versions, with a 500 KHz oscillator, and with a 1 MHz oscillator. Unique circuitry to accommodate different sensors, cable lengths, and target material (as necessary), is added to the Measuring Module in the form of a plug in circuit card. This small circuit card is called a “bridge card”. Some generalizations concerning the bridge card are: 1.
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6.5 Interchangeability of KDM-8200 & KDM-8206 Measuring Modules KDM-8206 and KDM-8200 Measuring Modules are physically interchangeable in a 3U/84HP rack enclosure. In general, a KDM-8206 Measuring Module can be used in a KDM-8200 rack and a KDM8200 Measuring Module can be used in a KDM-8206 rack enclosure. However, note the following comments and precautions: 1. The Euro connector pin outs for main connections (input power, ground, voltage output, sensor input) are identical on both systems. 2.
