Martel Electronics BetaGauge 321A - Manual (Page 16)

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Figure 5
Use the (ZERO) key to zero the pressure sensor when vented to atmospheric pressure.
Important NOTE: To protect sensor integrity and prevent damage to the sensor, the
calibrator will display OL [overload] when the applied pressure exceeds 120% of the full
scale calibrated range of the sensor.
Important NOTE: To ensure accuracy of the calibrator it is critical to zero the calibrator
before a device is calibrated.
3.1 Media Compatibility
The calibrator utilizes a media isolated sensor to prevent sensor contamination.
Whenever possible clean, dry air is the media of choice. If that is not always possible,
make sure that the media is compatible with Nickel Plated Brass and 316 Stainless Steel.
3.2 Measuring Pressure with External Modules
The calibrator provides a digital interface to External Pressure Modules. These modules
are available in various ranges and types including gauge, vacuum, differential and
absolute. The modules work seamlessly with the calibrator. Simply plug them into the
interface and select [EXT] (external sensor). Since the interface between the calibrator
and the module is digital all the accuracy and display resolution is derived from the
module.