Vega DSGH, Operating Instructions Manual

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DSGH Installation and Operation Guide 41
Calibration
C
H A P T E R
3
Chapter 3
C
ALIBRATION
Before using the gauge to make measurements, you must:
• Calibrate it to relate the detection of radiation from the source to the
density of the process material.
• Calibrate the current loop to a reference ammeter or the DCS.
• Periodically, you must standardize the system on process to adjust for
changes over time.
Calibration establishes a reference point or points that relate the detector
output to actual (or known) values of the process.
You must make a calibration before the gauge can make accurate
measurements. Perform the calibration after the installation and
commission of the gauge at the field site.
You do not need to repeat the calibration procedures if certain critical
process and equipment conditions remain unchanged.The gauge requires
only a periodic standardization to compensate for changing conditions
Current loop (analog output) calibration
Calibrating the current loop adjusts the 4 mA ... 20 mA output to a
reference, the PLC/DCS or a certified ammeter. It forces the 4 mA and
20 mA outputs to the external reference. The VEGA factory pre-adjusts the
current loop with a certified ammeter, so it is very close to the outputs
required.