PROGRAMMING OF VRAE
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Correction factors are often used to obtain a calculated
concentration of a specific gas while using a different gas
during calibration. When the unit is calibrated to %LEL
methane, the CF is multiplied by the reading to obtain the
true %LEL concentration of the measured gas. The factor
incorporates the difference in LEL levels of the two gases.
The VRAE monitor stores one set of correction factors for
the LEL sensor. This set consists of about 40 different
gases. The user can choose one gas from the list to be the
calibration gas and another gas to be the measurement gas.
For example, the user can choose methane as the calibration
gas for the LEL sensor and select pentane as the
measurement gas. The VRAE monitor will calculate the
correction factor between these two gases and convert the
measured value of the LEL sensor into equivalent
concentration of the pentane gas.
Note 1
: Using the correction factor can provide a rough
estimate the target measurement gas. In order to achieve the
specified accuracy of the instrument, it is necessary to
calibrate the LEL sensor with the specific target gas.
Note 2
: No correction factors are built in for the VOL
sensor, but selecting the measurement gas type in this mode
ensures switching between LEL and VOL at the correct
volume % concentration equivalent to 100% LEL. For VOL
measurements the calibration and measurement gas must be
the same, and the factor is always 1.0.
