Chapter 3 applications guide, 1 advice and tips, 1 what is the required warm up time – INFICON Composer Gas Concentration Controller User Manual
Page 63: 2 when and how often to set the reference zero, Chapter 3
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Composer Operating Manual
Chapter 3
Applications Guide
3.1 Advice and Tips
The following paragraphs review many of the common questions encountered
during setup and operation.
3.1.1 What is the Required Warm Up Time
Once the set point for the Transducer’s temperature is altered, it will take up to
15 minutes for the temperature to settle around the operating point. It may take
even more time if the temperature set point is lowered and is close to the
ambient temperature. Once the set point temperature is reached, the
instrument is ready to provide data. It is our experience that because of the
relatively low thermal conductivity of the materials used to construct the
Resonant Chamber that even after an hour there is still some small potential for
further reducing temperature induced speed of sound measurement errors. It is
easy to reset the Reference Zero frequency and eliminate these effects. It is
also expected that the Transducer will always be operating, so day to day
variations will be minimal because any long term thermal settling complications
will be absent. If the Ambient temperature changes, there may be some slight
variation on the temperature of the Resonant Chamber as the effective thermal
load changes. This can be ignored except for the most precise measurements
and over the most extreme temperature swings.
3.1.2 When and How Often to Set the Reference Zero
Normal operation will be enhanced by daily setting of the Reference Zero. This
mitigates any effects of slight variations in day to day delivery line pressure and
atmospheric pressure changes. If the frequency of the Reference Zero is
recorded every day, a record of instrumental performance is generated. This
makes it easy to determine if a mistake has been made due to careless
procedure by comparison to the previously recorded values. It would be
unusual for the instrument’s daily zero frequency to vary by more than about
0.2 Hz for Nitrogen and 0.8 Hz for Hydrogen. The instrument should be
immediately re-zeroed any time the pressure, flow rate or any other instrument
subsystem such a Mass Flow Controller, Back Pressure Controller or pressure
gauge is changed—even if it is the same type and uses the same settings. The
correct (user set) Reference Zero is retained until a new Reference Zero is
established or new carrier gas parameters are entered. User Reference Zero is
locked out if SW#6 CFGR1 is set, see
.