MiniRAE 3000 User’s Guide
39
Span Calibration
This procedure determines the second point of the sensor calibration
curve for the sensor. A cylinder of standard reference gas (span gas)
fitted with a 500 cc/min. flow-limiting regulator or a flow-matching
regulator is the simplest way to perform this procedure. Choose the 500
cc/min. regulator only if the flow rate matches or slightly exceeds the
flow rate of the instrument pump. Alternatively, the span gas can first
be filled into a Tedlar bag or delivered through a demand-flow
regulator. Connect the calibration adapter to the inlet port of the
instrument, and connect the tubing to the regulator or Tedlar bag.
Another alternative is to use a regulator with >500 cc/min flow but
allow the excess flow to escape through a T or an open tube. In the
latter method, the span gas flows out through an open tube slightly
wider than the probe, and the probe is inserted into the calibration tube.
At the Span Calibration menu, you perform a Span calibration. You
may also go back to the Zero calibration menu or to the initial
Calibration menu if you want to exit calibration.
• Press [Y/+] to enter Span calibration.
• Press [N/-] to skip Span calibration and return to Zero
calibration.
• Press [MODE] to exit Span calibration and return to the top
calibration menu.
If you have pressed [Y/+] to enter Span calibration, then you will see
the name of your Span gas (the default is isobutylene) and the span
value in parts per million (ppm). You will also see this message that
prompts you:
1. Turn on your span calibration gas.
2. Press [Y/+] to initiate calibration.
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