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Set the range of a Xenta 102-AX CO2 sensor


A Xenta 102-AX accepts a 0-5V input on all external inputs. If Universal Input 3 is designated as CO2, the range of the input needs to match the range of the sensor.

Product Line

EcoStruxure Building Operation, TAC Vista


  • Xenta 102-AX
  • Universal Input 3
  • CO2 sensor


The default setting (a gain of 1/1) results in

  • 0V = 0ppm
  • 5V = 1023ppm

(1023 is a resolution of the onboard analog to digital converter.)


Refer to page 3-66 of the TAC Xenta 102-AX Software & Hardware Manual for more detail.

  1. Calculate the required gain for the range of the CO2 sensor.
    1. Ensure the sensor outputs a 0-5V signal.
    2. Note the CO2 level at 5V. In this example, 2000ppm.
    3. Divide the maximum CO2 reading by the analog to digital converter bit resolution (1023).
    4. Multiply the result by 1000.
    5. (2000 / 1023) * 1000 = 1955
  2. Locate the value for Universal Input 3 SCPTgain. There are four locations to alter this value:
    1. Xenta 102-AX Plug-in
      Go to the Browser Tab > Xenta102AX > UnivIn3 Sense > SCPTgain > multiplier. Over on the right, enter in 1955/1000 and hit Set Value.
    2. LonMaker or LNS browser
      Open the browser window by right clicking on the 102-AX in the drawing and selecting Browser. Look in the Functional Block column for UnivIn3Sense. In that category is a point called SCPTgain. Click on it and then enter up top 1955/1000. Hit the red down arrow to download the value to the device. Enable monitoring on the nvoCO2sensor value or reopen the browser to view the new CO2 value.
    3. Vista Workstation
      Go to the 102-AX.UnivIn3_Sense module and locate the SCPTgain point. Double click it. By Multiplier enter 1955 and by Divisor enter 1000.
    4. StruxureWare WorkStation
      Go to the 102-AX and click on UnivIn3Sense module and in the Variables tab locate the nciGainUIx point and expand it. For Multiplier, enter 1955 and save. For Divisor, enter 1000 and save.
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