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10. PRINCIPLES OF OPERATION
10.1. BASIC PRINCIPLES OF DYNAMIC DILUTION
CALIBRATION
The T700 Dynamic Dilution Calibrator generates calibration gas mixtures by mixing
bottled source gases of known concentrations with a diluent gas (zero air). Using
several Mass Flow Controllers (MFCs) the T700 calibrator creates exact ratios of diluent
and source gas by controlling the relative rates of flow of the various gases, under
conditions where the temperature and pressure of the gases being mixed is known (and
therefore the density of the gases).
The CPU calculates both the required source gas and diluent gas flow rates and controls
the corresponding mass flow controllers by the following equation.
Equation 10-1
Totalflow
GAS
CC
flow
if
×=
WHERE:
C
f
= final concentration of diluted gas
C
i
= source gas concentration
GAS
flow
= source gas flow rate
Totalflow = the total gas flow through the calibrator
Totalflow is determined as:
Equation 10-2a
TOTALFLOW = GAS
flow
+ Diluent
flow
WHERE:
GAS
flow
= source gas flow rate
Diluent
flow
= zero air flow rate
For instrument with multiple source gas MFC total Flow is:
Equation 10-2b
TOTALFLOW = GAS
flow MFC1
+ GAS
flow MFC2
…+ GAS
flow MFCn
+ Diluent
flow rate
06873B DCN6388