Martel Electronics BetaGauge 321A - Manual (Page 11)

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2.2 Using the Backlight
The backlight is controlled by the dedicated backlight key. It toggles on and off when the
key is pressed; this is one of the few functions that cannot be controlled by the serial
interface. There are no user configuration settings for the backlight.
2.3 Using the Zero Function
When the ZERO KEY is pressed, the calibrator will zero the current display if a pressure
mode is selected, and the pressure is within the zero limit. The zero limits are within 5% of
the full scale range of the selected sensor. If the display indicates “OL,” the zero function
will not operate.”
2.3.1 Internal Sensor and Pressure Module (non-absolute)
When a sensor or module is selected on the current display and the ZERO KEY is
pressed the calibrator subtracts the current reading from the output. The zero limits are
within 5% of the full scale range of the selected sensor. If the display indicates “OL,” the
zero function will not operate.
2.3.2 Absolute Internal Sensor or Absolute Pressure Module
When an absolute module is selected on the current display and the ZERO KEY is
pressed, the calibrator prompts the user to either set or default the pressure reference.
If the set option is selected, the calibrator prompts the user to enter the barometric
reference pressure. This is done using the arrow keys (F2 and F3 keys). The sensor port
should be open (vented) to atmosphere while performing this procedure.
Alternately, if the DEFAULT option is selected, the user is asked to confirm the choice to
go to factory default or cancel the request.