Calibration and Spectrum Troubleshooting: Span Calibration (Series Part 3 of 4)

Calibration and Spectrum Troubleshooting: Span Calibration (Series Part 3 of 4)

In the previous blog, we learned about the general process for zero calibrations for AirSentry® II analyzers. In this entry, we learn how the next step after installation, span calibrations, empirically determine the influence that local atmospheric pressure has on AMC detection.

Before you begin, the reactant peak (charged dopant) and target peak (charged AMC) should be identified in the drift time windows. This is done during zero calibration.


After the first step, the software process takes an average of 5 minutes.

  1. Deliver 25 ppb calibrant gas to the ASII sample inlet for 30 to 60 minutes.
  2. After achieving a steady-state concentration, initiate span calibration using the service software. Set the sample interval to 300 (seconds).
  3. The algorithm will measure the heights of each peak for the known 25 ppb concentration.
  4. The peak height values found in the target and reactant windows are extracted by the software.
  5. Local maxima are found in each window.
  6. The algorithm uses concentration calculations to determine the measured concentration in parts per billion.
  7. A simple multiplicative correction span factor is found and multiplied by the calculated concentration. The span factor is multiplied to account for local atmospheric pressure on the AMC-to-dopant peak ratio.

Set the analyzer to “Norm” mode to apply the new span factor. Below are acceptable ranges for the span factor for each type of analyzer.

Download the paper to learn more about the span calibration process. Also look forward to our next blog in this series that covers troubleshooting abnormal IMS spectrums seen during operation of the analyzer.

Click here to learn more about innovative AMC monitoring solutions to help you quickly identify problems and their location before your product is contaminated: AirSentry II Point-of-Use Ion Mobility Spectrometer

Want to read more? Jump to other released posts in this series:

Part 1 of 2: IMS Spectrum Introduction, Measurement and Calibration

Part 2 of 4: Zero Calibration

Part 3 of 4: Span Calibration (You are here!)

Part 4 of 4: Troubleshooting Abnormal IMS Spectrums

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