INFICON Composer Gas Concentration Controller - Manual (Page 192)

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Composer Operating Manual
Resonant Mode
A standing acoustic wave. The lowest frequency mode is called the
fundamental.
Root Allan Variance
A measure of short term stability that is the square root of the sum of
the difference between successive measurements squared.
sccm
Standard Cubic Centimeters per Minute, a measure of gas flow rate.
Self Resonance
A term that refers to the possible vibration modes of the individual
components in an acoustical system. It is desirable that the Self
Resonance of all of the individual components in the transducer be at a
higher frequency than the normal operating frequency range of the
instrument.
Specific Heat Ratio
The ratio of the specific heats of a gas, namely the ratio of the specific
heat at constant pressure to the specific heat at constant volume, C
p
/
C
v
(noted as γ on the LCD Display). This is used as a physical
parameter for the calculation of binary gas concentration by the
measurement of the speed of sound through the binary gas.
SPST
Single Pole Single Throw - A description of a relay’s contact
configuration.
Standing Acoustic Wave
A stationary acoustic wave that exists in the resonant chamber when
the exciting frequency develops a wavelength exactly twice as long as
the chamber. When this wave is at the fundamental frequency it will
have the maximum amplitude possible for the existing conditions of
gas, composition temperature and pressure.
TOF
Time of Flight, a method of determining the speed of sound by
measuring the time interval for an acoustic pulse to travel a known
distance.
TMGa
trimethylgallium
TMIn
trimethylindium