Analytical Industries GPR-7500 AIS Trace PPM Hydrogen Sulfide Analyzer - Manual (Page 18)

Advanced Instruments, Inc.
18
Span Gas Preparation
Note: The GPR-7500AIS can be calibrated by using a certified span gas, preferably 50-80% of the full scale
of the least sensitive range. After initial calibration, subsequent calibration should be carried out by using a
span gas between 50 to 80% of the range of interest or one range above the range of interest.
Caution: Do not inhale the H
2
S span gas. If the analyzer is installed in an enclosed area, when
using a span gas, ensure the area is being ventilated by circulating air to flush out H
2
S.
Required Components
1. Certified span gas cylinder with an H2S concentration, balance nitrogen or air, approximating 50-80% of
the full scale of the measuring range or one range above the intended measuring range. For example,
for analysis on 0-500 PPM range, use a span gas with H2S concentration ranging from 250-400 PPM
2. A pressure regulator to set the span gas pressure between 5 and 30 psig.
3. A flow meter to set the flow between 1-5 SCFH (if the transmitter is not equipped with a flow meter),
4. Suitable tube fittings and a 4-6 ft. length of 1/8” dia. metal tubing to connect the cylinder regulator to the
flow meter inlet. (bypass step 4, 5 if the transmitter is equipped with a flow meter and connect the tubing
from regulator directly to the SPAN inlet of the transmitter)
5. Suitable tube fittings and a 4-6 ft. length of 1/8” dia. metal tubing to connect from the flow meter vent to
tube fitting designated as SAMPLE IN or SPAN IN at the analyzer.
Procedure
1. With the span gas cylinder valve closed, install the pressure regulator on the cylinder.
2. Keep the regulator’s exit valve closed and open the cylinder’s control knob slowly.
3. Open the cylinder valve completely.
4. Set the pressure between 5-30 psig using the pressure regulator’s control knob.
Caution: Do not exceed the recommended flow rate. Excessive flow rate could cause the backpressure on
the sensor and may result in erroneous readings and damage the sensor