Zero Calibration – Menu Page 18

This page is used to zero the IR cells. It is very important to be sure that the sample gas is a good zero especially for CO2. Ambient air has nominal percentage of CO2, which should not be present when performing a zero calibration.  It is recommended that 99.9% pure nitrogen be used for zeroing the PGA3500. If there is no nitrogen present, the CO2 Scrubber (P/N 13112) can be used to remove the CO2 from ambient air.  The sample gas flow rate should be between 1 and 1.5 SCFH.

 

When viewing this screen, the current measured values are shown at the left under the heading Actual, while the desired values will be in the center column, Zero Gas.   The final column is Status, and this shows the percentage difference between the actual and desired values, followed by a comment.  This comment can either be OK, ?OK, or BAD, depending on how far apart the values are.  If the difference is between 0 and 10% of the span value, then it will be OK and the calibration will proceed without interruption.  If the difference is between 10% and 20%, it will be ?OK, and a warning message will be displayed.  Pressing Enter will allow the calibration to continue.  If the value is more than 20% out, it will be BAD and the calibration will not be allowed to proceed.  If this occurs, check to make sure that you are using the correct gas and that there is adequate flow.  If it is still not operating properly contact SSi for additional support.

 

It is possible to calibrate one, two, or all three sensors.  The default setting is to calibrate all three, however if you do not want to calibrate one of the sensors you can use the up and down arrows to access the sensor that you do not want to calibrate, and press Enter over the existing Yes.  This will change it to No, and that sensor will not be calibrated.

 

To proceed with the calibration of one or more sensors, use the arrow key to move to the Start button and press Enter.  Timers will count down approximately two minutes and at the conclusion the sensors will be calibrated.

 

WARNING: Do not pressurize PGA3500 with compressed gas.  Always start the flow of Nitrogen and regulate prior to connecting to PGA3500 inlet.