Alco-Sensor III Accuracy Check Procedure - Page 3

Accuracy Check -  Alco-Sensor III

  1. You should know the expected value of the standard – this will be used to compare against the actual result determined by the instrument.
  2. The True-Cal II device displays .081, this is the expected value of the Standard used for this demonstration.




  1. Submit a gas sample from the standard to the Alco-Sensor III for at least six (6) seconds. On the 4th or 5th second of the count, depress the read button and hold it down.

  2. (NOTE: The vapor must continuously flow
    through the mouthpiece until one second after the read button is depressed).

  3. Continue to hold the read button until the displayed result stablizes for 5 to 6 seconds. 


Submit a gas sample

READ button is depressed


  1. Carefully detach the Alco-Sensor III from the standard and observe the displayed reading until it becomes stable for 5 seconds. The stable number is the final result.
  2. The difference between the final result and the expected value of the standard should be within the tolerance allowed in the Quality Assurance Plan set for your program.
  3. If the difference is greater than the specified tolerance, the unit requires a calibration adjustment.  (Follow instructions for CALIBRATION).
  4. The expected value of the standard used for this demonstration was .081, so our result of .080 is within an acceptable tolerance
Observe the final result
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