INFICON DataFID Portable Flame Ionization Detector for Leak Detection and Repair (LDAR) - Manual (Page 63)

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DataFID Calibration
Calibration Technical Description
The DataFID will always detect all ionizable compounds present in a sample regardless of the
response factor (RF) selected.
NOTE: Even if the DataFID has been calibrated with a specific compound, its response is not
specific and the presence of another ionizable impurity may render the numerical result invalid.
It is often impractical to carry a range of different standards into the field. Approximate results
can be obtained by calibrating the DataFID with the recommended span gas and entering the
appropriate response factor. The response factor is based on the ratio of the response of the
specific compound to the response of the span gas. The response factor multiplies the
DataFID
’s reading, then displays and records it.
NOTE: The DataFID is a total VOC instrument and will ALWAYS respond to all ionizable
compounds present in a sample. The DataFID will NOT respond only to a specific compound if
an RF is programmed. It is the responsibility of the user to be aware of the limitations of Flame
Ionization Detection instruments.
Calibration is required for the DataFID to compensate for temperature/climate changes as well
as output changes due to inlet filter restrictions, ionization chamber cleanliness, sample pump
wear and other factors. It is also needed in order to display concentration in ppm units
equivalent to the calibration gas.
During calibration, the DataFID is first exposed to zero air which contains no ionizable gases or
vapors. It is used to set the DataFID
’s zero point. A small signal is generated and the zero
signal is stored by the microprocessor.
DataFID is next exposed to span gas. This span gas signal is stored by the microprocessor. The
microprocessor subtracts the zero signal from the span gas signal and divides the difference by
the user-entered span gas concentration. The resulting sensitivity is stored in the selected Cal
Memory with the zero signal and the alarm level. This number is then multiplied by the response
factor and displayed.
DataFID readings are always relative to the calibration gas. After calibration with a span gas,
DataFID will respond directly in units equivalent to that span gas. Almost all combustible organic
compounds will be detected by DataFID. It cannot distinguish between the selected calibration
gas and other ionizable compounds. A reading of 10 ppm indicates all ionizable compounds that
are present have generated an ion current proportional to 10 ppm of the selected calibration
gas. DataFID readings give an indication of the total ionizables present and their concentration
relative the calibration gas.
Due to the DataFID
’s sensitivity, outdoor air is usually unsuitable for calibration. A charcoal filter
(Part No. MX396022) may be connected to the instrument to produce clean air from otherwise
unsuitable ambient air. For best results, use a commercial source of zero grade air and a
second sampling bag. Zero air should have not more than 0.1 ppm total hydrocarbons (THC).