Electronic Flow Sensor (Efs) Calibration; Setting The Zero Calibration Value - HP 5890 SERIES II Service Manual

Electronic Flow Sensor (EFS) Calibration

Electronic flow sensor (EFS) calibration may be performed any time to ensure displayed flow rate accu-
rately represents real gas flow rate through the sensor. The EFS is factory calibrated for four standard
gases, H2, He, N2, and Ar/CH4, 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 H2, He, N2, or Ar/CH4), 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).
IF CALIBRATION IS BEING PERFORMED FOR H2, OBSERVE PROPER SAFETY
PRECAUTIONS TO PREVENT A FIRE OR EXPLOSION HAZARD.
Prior to performing the calibration procedure, the following must be done:
The instrument must be on for at least one hour for thermal equilibration of the EFS.
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Since gas flow through the channel to be calibrated will be interrupted, detectors should be
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turned off (particularly an NPD or TCD! ), and the oven cooled to ambient temperature (to
protect columns).
A flow measuring device is required, accurate to better than 1 ml/min.
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The EFS is calibrated to measure volumetric flow at standard temperature and pressure.
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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.
Preparation
1. Access the EFS by removing the left side panel; remove two screws along its lower edge, slide
the panel toward the rear of the instrument, and then lift.
2. Through the keyboard, select CALIB AND TEST mode, function 2:
GAIN A is displayed, followed by two values: the observed flow rate through Channel A, and the current
GAIN calibration value for Channel A.

Setting the ZERO Calibration Value

The ZERO calibration value MUST be set with NO gas flow through the channel being calibrated.
1. Press : FLOW A ZERO is displayed, followed by a value (the current ZERO calibration
ZERO
value for EFS Channel A). Note that Channel A is assumed by default; if channel B is to be cali-
brated instead, press
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.
B
SVC 3- 22
.
2
CLEAR ENTER