Advanced Instruments, Inc.
Span Calibration
Span Gas Preparation
One of the most accurate, reliable and inexpensive means of calibrating the GPR-2500A is to expose the
sensor to the 20.9% oxygen content found in ambient air. However, exposing the sensor to ambient air
with the GPR-2500A flow through configuration requires opening the enclosure and unscrewing the
sensor from its flow housing. However, many users opt to calibrate with a certified span gas which
requires additional components and time.
Caution: When using a certified span gas from a span gas cylinder, do not contaminate the span gas
cylinder when connecting the pressure regulator. When installing the pressure regulator, bleed the air
filled regulator to flush air from the regulator before securing it on the cylinder. When using a span gas,
always bleed the pressure regulator before opening the span gas to the analyzer (this requires a bypass
valve at the exit of the pressure regulator valve).
Note: Always use a certified span gas with an oxygen concentration, balance nitrogen, approximating
50-80% of the full scale range of interest or one range above the intended measuring range. You will
require the following components to deliver a span gas to the analyzer/transmitter.
Set the span gas pressure as close as possible to the sample gas pressure. This will assure a smooth shift
from sample to span or vise versa without the need to readjust the gas flow rate.
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