Dilution Principle; Figure 1 Dilution Principle - M&C SP Series Instruction Manual

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Dilution principle

The functional principle of the dilution unit is based on ultrasonic flow through a critical orifice (see Fig.
1). The flow through the orifice is constant when the differential pressure via the orifice is higher than
500 mbar. For the atmospheric inlet pressure (P
outlet (P ) of less than 520 mbar absolute.
OUT
The necessary vacuum at the orifice outlet is produced by an injector operated with dilution gas.
Depending on the critical orifice and injector type, dilution rates can be between 10:1 and 500:1 for
injector I. The table below gives an overview of the dilution factor and sample gas volume using the
injector I (480 – 600 Nl/h):
Orifice type
Dilution ratio*
Volume flow through the orifice [Nl/h]
* With injector II 50:1 to 2000:1
Critical
Orifice
P
IN
Figure 1 Dilution principle
Checking the dilution ratio and excact adjustment of the pressure ratios are descriped in chapter 17.1.
16
IN
Dilution Gas IN
Injector
P
OUT
SP190-H/DIL-EX2 T* | 1.01.00
= 1020 mbar), this means a pressure at the orifice
a b c
500:1 200:1 100:1 50:1
1.4 2.7 5.5
E.g.:
P = Atmospheric pressure (1020 mbar)
IN
P < 520 mbar abs. (low pressure)
OUT
⇒ Differential pressure at the orifice > 500 mbar
⇒ Constant flow
d e f
30:1 20:1 10:1
11 19 28
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