User guide

4 - 1
PN 074-566-P1B
Composer Elite Operating Manual
Chapter 4
Applications Guide
4.1 Advice and Tips
The following paragraphs review many common questions encountered during
setup and operation.
4.1.1 What is the Required Warm Up Time?
Once the setpoint for the Acoustic Sensor’s temperature is altered, it will take up to
thirty minutes for a single Acoustic Sensor’s temperature to settle around the
operating point. It may take even more time if the temperature setpoint is lowered
and is close to the ambient temperature (refer to section 2.1.1.3, Heated Process
Tubing and Acoustic Sensor Temperatures, on page 2-2).
Once the setpoint temperature is reached, Composer Elite 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, even after an hour there is still
some small potential to further reduce temperature induced speed of sound
measurement errors. It is easy to reset the Reference Zero frequency and
eliminate these effects (refer to section 3.2, Calibration, on page 3-2).
It is also expected that the Acoustic Sensor will always be operating, minimizing
day-to-day variations 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.
4.1.2 When and How Often to Set the Reference Zero
Normal operation will be enhanced by daily Calibration to set Reference Zero (refer
to section 3.2, Calibration, on page 3-2). This mitigates any effects of slight
variations in day-to-day process tubing pressure and atmospheric pressure
changes. If the frequency of the Reference Zero is recorded every day, a record of
Composer Elite 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 Composer Elite’s daily Reference Zero
frequency to vary by more than about 0.2 Hz for nitrogen and 0.8 Hz for hydrogen.
Calibration should be immediately performed any time the pressure, flow rate or
any other Composer Elite subsystem such as a Mass Flow Controller, Back
Pressure Controller or pressure gauge is changed — even if it is the same type and
uses the same settings.