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Span Calibration

This calibration process entails adjusting the sensor's span by identifying a time frame where the gas concentration reaches a maximum reference value, or alternatively, a significantly high value. This adjustment allows for the modification of air quality sensors' sensitivity, resulting in appropriate changes to the concentration span.
In order for this procedure to work, you need to make sure that you have already uploaded a reference data of the targeted gas. If you haven’t done this step kindly click this link for more details.

Calibration Steps:

(Note: The following steps are applicable only if you didn’t proceed from baseline calibration)
  1. Select Device and Reference Station
      • In this step, you need to select following:
        • Type - refers to calibration type. Select “Span”.
        • Installation - refers to your device installation
        • Gas Sensor - refers to the sensor you want to calibrate
        • Reference Station - refers to the reference station / device that contains the reference data of the targeted gas.
        • Figure 1 - Select Device and Reference Station
          Figure 1 - Select Device and Reference Station
  1. Select periods for baseline and span
      • In this step you need to select two periods for baseline and span.
      • Select the period with the lowest gas reference value for the baseline (B1 - B2).
      Figure 2 - Select the period with the lowest gas concentration for baseline.
      Figure 2 - Select the period with the lowest gas concentration for baseline.
      • While select the period with the highest gas reference value for the span (S1 - S2).
      Figure 3 - Select the period with the highest gas concentration for span.
      Figure 3 - Select the period with the highest gas concentration for span.
      • Each time you select a period, you would be asked where to assign it, baseline or span.
      Figure 4 - Assign selected period
      Figure 4 - Assign selected period
      Note: Baseline calibration is prerequisite in order for the span calibration to work.
  • Once you’re done selecting the two periods, the “Analyze” button will appear. Kindly review if the selected periods are correct, before clicking it.
    • B1 - B1 represent the selected range for the baseline.
    • S1 - S2 represents the selected range for the span.
Figure 5 - Selected period to analyze
Figure 5 - Selected period to analyze
  1. Select baseline offset and span factor
      • In this step you would be asked to select the baseline offset and the span factor.
      • Baseline:
        • You can select the baseline offset from the minimum concentration or the average / mean.
          • Min - Offset constant was computed using the lowest reference value.
          • Mean / Average - Offset constant was computed using the mean reference value.
        • Or you can specify the offset that you prefer (don’t forget to click “use” to use the value from this field)
      Figure 6 - Baseline offset selection
      Figure 6 - Baseline offset selection
      • Span
        • You can select the span factor from the maximum concentration or the average / mean.
          • Max - Offset factor was computed using the highest reference value.
          • Mean / Average - Offset factor was computed using the mean reference value.
        • Or you can specify the factor that you prefer (don’t forget to click “use” to use the value from this field)
      Figure 7 - Span factor selection
      Figure 7 - Span factor selection
      • Once baseline and span are set, the “compute” button would be enabled. Click this to view the “Corrected Values” line series. This series represents the adjusted values based on the offset and span factor that you have selected. It will appear as a “blue” line.
      • A Pearson correlation chart will also appear to show the linear relationship between the reference data and the corrected values.
Figure 8 - Corrected Values
Figure 8 - Corrected Values
  1. Apply Calibration
      • Once you’re done selecting the baseline offset and the span factor, you can apply the result to the gas sensor by clicking the “Apply Calibration”.
      • This will send request to the server, that you want to apply the selected baseline offset to the “offset constant”, and the span factor to the “offset factor”, of the gas sensor settings.
      • The request will be applied on the next polling interval of the device.

Calibration Steps - From Baseline calibration:

(Note: The following steps are applicable only if you clicked “yes” when asked if you want to proceed with span calibration, during the last step of the baseline calibration)
  1. Select a period when gas concentration reached maximum.
      • In this step, you will be asked to select a period when gas concentration reached its maximum or highest reference value. Simply highlight a portion of the chart to select a period.
      Figure 9 - Select highest reference value
      Figure 9 - Select highest reference value
      • An “Analyze” button will show up on the screen. Review the selected period first, before clicking it.
      Figure 10 - Review the period before analyze
      Figure 10 - Review the period before analyze
  1. Select the span offset factor
      • In this step, you will be asked to choose the span offset factor.
        • Max - Offset factor was computed using the maximum reference value.
        • Mean / Average - Offset factor was computed using the mean reference value.
        • Specific - Or you can specify the factor that you prefer in the input field (don’t forget to click “use” to use the value from this field)
      Figure 11 - Select offset factor
      Figure 11 - Select offset factor
      • Once the offset factor is selected, the “Corrected Values” will be displayed on the chart. This series represents the adjusted values based on the offset (set during baseline calibration) and span factor that you have selected. It will appear as a “blue” line.
      • A Pearson correlation chart will also appear to show the linear relationship between the reference data and the corrected values.
      Figure 12 - Corrected Values
      Figure 12 - Corrected Values
  1. Apply Calibration
      • Once you’re done selecting the span factor, you can apply the result to the gas sensor by clicking the “Apply Calibration”.
      • This will send request to the server, that you want to apply the span factor to the “offset factor” of the gas sensor settings.
      • The request will be applied on the next polling interval of the device.