203M User Manual Publication No. 980978 Rev. A
Operation 2-2 Astronics Test Systems
METER RANGE Switch
The METER RANGE Switch has three positions to select: 10, 100, or 1000 units
full scale. The DC OUTPUT is 10 Volts full scale for each range
Sensitivity (RANGE) 1-11 or 10-110 Switch
The two-position SENSITIVITY Switch is a range selector for the variable
sensitivity control. The proper range selection and sensitivity control setting
allows using pickups from 1 to 110 pC/g or mV/g sensitivities. Place this switch
to the range the pickup sensitivity falls in. For instance, if the pickup is 20 pC/g,
the 10 to 110 range is selected.
SENSITIVITY Control
The sensitivity control is a calibrated ten-turn potentiometer to provide a
continuously variable sensitivity for each range selected by the SENSITIVITY
RANGE switch. For the above example, the control will be set for 2.0
SE-DIFF Switch
This switch permits selection of a single-ended input (SE) or Differential Input
(DIFF). When the DIFF position is selected, the common mode rejection can be
adjusted by the DIFF ADJ control, a screwdriver adjustment immediately below
the DIFF position of the switch. If operating with a pickup that is insulated (no
ground) the single-ended (SE) position should be used. When the pickup
common is grounded, the Differential (DIFF) input opens the ground path
between the pickups and the amplifier and provides rejection of the common
mode voltage.
OPER-CAL Switch
The OPER-CAL switch selects either the ACCEL input when in OPER, or the
internal calibrator input when in the CAL position. The internal calibrator level
can be monitored at the CALIBRATION INPUT BNC connector just below the
OPER-CAL switch. When the OPER-CAL switch is in the OPER position, the
calibrate mode can be selected from a remote CAL CONTROL line. When the
CAL mode is selected, either by the front panel switch or the remote CAL CONT
line, the CAL LIGHT just to the right of the switch illuminates, and the meter
should read 100 ±3 g’s or 100 ±5 MILS.
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