Capacitive Sensors FAQ

Linear output circuitry produces a very linear output. In addition, they are factory calibrated to maximize the linearity of the output over the selected calibration range. Errors in linearity are usually less than 0.1%. This linearity calibration is in addition to the calibration of sensitivity and zero.

Analog output circuitry does not produce a linear output. Drivers are not calibrated for linearity. They are only adjusted for sensitivity and zero. These adjustments are accessible to the operator and are generally used where the system is calibrated to a master part or condition, and then used to adjust or notify when the tested part or condition exceeds a trip point. High degrees of linearity are not necessary in these types of applications.
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The LED Bar Graph is internally calibrated to the first stage of the probe amplifier. It is adjusted to indicate where the probe is in terms of its calibrated range, not the driver output voltage.

The LED Bar Graph is unaffected by adjustments to the front panel zero control. Therefore, the LED Bar Graph indicates whether or not the probe is in its calibrated range, independent of the output voltage.

The zero control can adjust the output voltage to produce what appears to be a legitimate reading even when the probe is actually out of range. The LED Bar Graph warns the operator with red lights (or computer when monitoring the Out of Range signals), that the measurement may not be accurate.
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Yes. Probes are calibrated to specific drivers. Even if it is the same model probe and driver with the same calibration, accuracy will be affected if the probes are not kept with their calibrated drivers. For this reason, in multi-channel systems probes and drivers are tagged with channel numbers. The calibration report that comes with the system will list the serial numbers of the matched driver and probe. Most systems include calibration stickers which list the serial numbers of the probe and driver that are calibrated together.
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Target shape is a major factor in measurement accuracy. Factory calibrations are done with flat targets. When other shape targets must be measured, custom calibrations can be done to the final target, or multipliers can be determined to correct the measurement. For more detail see the Target Shape section of our Capacitive Sensor Operation TechNote.
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Generally speaking, the resolution of a measurement system is a percentage of range. If range increases, the smallest measurement that can be made (resolution) also increases. Typical resolution values are 1 part in 10,000 or 1 part in 15,000. Different calibrations allow the user to optimize the combination of range and resolution.

These drivers contain circuitry for two separate calibrations. This switch selects the calibration to be used. Typically, there are two calibrations for the same probe; one calibration may be a standard calibration (low sensitivity) while the other may be Fine or Ultrafine for maximum resolution (high sensitivity).
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Standard cable length is 6' (2m). Lion Precision uses a high frequency (1MHz) probe signal to increase bandwidth of the measurement. For this reason, the cable length does affect the calibration, so the probe must be calibrated with its final cable length. Extension cables would adversely affect the operation. Custom cable lengths can be ordered. At lengths over 10' (3m) the probe drive frequency may have to be reduced to 500kHz, lowering the measurement bandwidth.
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The TMP190 and TMP72 are used with the Spindle Error Analyzer to monitor machine tool temperature during spindle error motion tests. They require a computer interface to select active sensors and gather the measurements.
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