MTI AccuMeasure 9000, Руководство пользователя

Страница: 7 / 32

1
1 INTRODUCTION
1.1 Accumeasure™ 9000 System Description
The Accumeasure System 9000 amplifier is a high-precision single or dual-channel capacitance probe
amplifier that uses standard or custom MTI noncontact probes. Its analog output voltage is proportional to
the gap between a probe and its measurement target. A front-panel bargraph is available for each probe
channel to indicate the probe gap value. This indicator is used for initial probe gap setup and for periodic
monitoring of the magnitude of the average gap. An optional digital panel meter is available in place of the
bargraph to provide a numerical indication of the probe gap. This meter is calibrated to indicate a voltage
reading proportional to the rear panel output signal voltage.
The probes measure displacement from the probe face to the target and are connected to the amplifier
with special low-noise coaxial cable. The cable’s outer shield is electrically driven to cancel the cable’s
parasitic capacitance and ensure the highest linearity. Front-panel gain and offset controls permit minor
adjustments of the probe calibration characteristics.
An internal 5-pole Butterworth low-pass filter removes unwanted high-frequency noise for the best
resolution possible. Optional filter cutoff frequencies of 10 Hz, 500 Hz, 1 kHz, 2 kHz and 5 kHz are
available.
Two separate factory preset calibrations are offered. The primary calibration produces an analog output
proportional to the probe range divided by 10 volts. For a probe with a 1mm (0.039inch) range and a 10V
full-scale output, the analog output is 0.1mm per volt (0.0039inches per volt).
The second type of calibration produces a normalized 0.025

m per millivolt (0.98 micro-inch per millivolt)
calibration slope when used with any MTI probe. With this type of calibration, a 1mm (0.039 inch) range
probe would have a range of 200

m (7.8mils), a 0.025

m per millivolt (0.98 micro-inch per millivolt)
sensitivity factor, and a standoff of 1mm (0.039 inches). The advantage of this type of calibration is that
any probe type will have the same sensitivity factor of 1 micro-inch per millivolt, regardless of its range.