Electronic Flow Sensing
Electronic flow sensor (EFS) calibration
Electronic flow sensor (EFS) calibration
Electronic flow sensor (EFS) calibration may be performed any time to ensure displayed flow rate accurately represents real gas flow rate through the sensor. The EFS is factory•calibratedfor four standard gases, H1, He, N1, and Ar/CH3, within the flow rate range of 0 to 100 ml/min. This covers the majority of chromatographic applications.
Two situations where it would be appropriate to perform recalibration would be where a nonstandard gas is to be used (e.g., something other than H1, He, N1, or Ar/CH3), or if flow rates in excess of 100 ml/min are to be used.
EFS calibration requires setting two values for a given flow channel•first, the zero value (defined with no flow through the given flow channel) and then the gain value (calculated, based upon a measured flow rate value).
WARNING If calibration is being performed for H2, observe proper safety
precautions to prevent fire or explosion hazard.
Prior to performing the calibration procedure, the following must be done:
CThe instrument must be on for at least one hour for thermal equilibration of the EFS.
CSince gas flow through the channel to be calibrated will be interrupted, detectors should be turned off (particularly an NPD or TCD! ), and the oven cooled to ambient temperature (to protect columns).
CA flow•measuringdevice is required, accurate to better than 1 ml/min.
CThe EFS is calibrated to measure volumetric flow at standard temperature and pressure. Flows measured at ambient temperature with a bubble flow meter will have to be converted from ambient temperature and pressure to standard temperature and pressure.
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