Here, the dilution flow is calculated from the gas concentration to be generated by the Permeater.
Permeater PD1B2/PD1B*
*PD1B is discontinued in October 2022.
Desired gas concentration
 ppm
Calculated value of the dilution gas flow
 mL/min (  L/min)
Flow that can actually be set  Generated gas concentration 

In order to increase the flow of the dilution gas without changing the generated concentration
 Enter a high numerical value of the permeation rate Pr from the numerical values indicated on the label on the permeation tube storage container.
→ If the set temperature is high, the permeation rate will increase, enabling the flow to be increased without changing the generated concentration.  In the case where there are several types of permeation tubes, change the type to one that enables a higher concentration to be generated. (For details, see the Permeater catalog.)
→ The permeation tubes that enable a high concentration to be generated have a large permeation rate, and enable the flow to be increased without changing the generated concentration.  Increase the number of permeation tubes.
→ If the number of tubes is doubled without changing the generated concentration, the flow will be roughly doubled.
In order to reduce the flow of the dilution gas without changing the generated concentration
 Enter a low numerical value of the permeation rate Pr from the numerical values indicated on the label on the permeation tube storage container.
→ If the set temperature is low, the permeation rate will decrease, enabling the flow to be reduced without changing the generated concentration.  If there are a number of types of permeation tubes, change them to a type that enables a lower concentration to be generated. (For details, see the Permeater catalog.)
→ A permeation tube that enables a low concentration to be generated has a small permeation rate, and enables the flow to be reduced without changing the generated concentration.  Reduce the number of permeation tubes.
→ If the number of tubes is halved without changing the generated concentration, the flow will be roughly halved.
Calculation of dilution gas flow
The dilution gas is calculated using the following equation:
F＝K×Pr×LC
 F：
 Flow of dilution gas (mL/min)
 C：
 Gas concentration for calibration gas (ppm)
 Pr：
 Permeation rate (ng/min/cm)
 L：
 Effective length of tube (cm)
 K：
 Coefficient for converting the gas weight into volume (L/g)
K＝22.4M× 273+t273× 760P
 M：
 Molecular weight
 t：
 Temperature
 P：
 Pressure (mmHg)
Diffusion tube  Desired gas concentration  Dilution gas flow Calculated value  Flow that can actually be set  Generated gas concentration 

In order to increase the flow of the dilution gas without changing the generated concentration
 Increase the set temperature.
→ If the set temperature is high, the diffusion rate Dr will increase, enabling the flow to be increased without changing the generated concentration.
In order to reduce the flow of the dilution gas without changing the generated concentration
 Reduce the set temperature.
→ If the set temperature is low, the diffusion rate Dr will become small, enabling the flow to be reduced without changing the generated concentration.
Calculation of dilution gas flow
The dilution gas is calculated using the following equation:
F＝K×Dr×10^{3}C
 F：
 Flow of dilution gas （mL/min）
 C：
 Gas concentration for calibration gas (ppm)
 Dr：
 Diffusion rate (µg/min)
 K：
 Coefficient for converting the gas weight into volume (L/g)
K＝22.4M× 273+t273× 760P
 M：
 Molecular weight
 t：
 Temperature
 P：
 Pressure (mmHg)
Diffusion tube for multiple components  Desired gas concentration  Dilution gas flow Calculated value  

First tube   
ppm 
mL/min (L/min) 
Second tube   
ppm 
mL/min (L/min) 
Third tube   
ppm 
mL/min (L/min) 
Fourth tube   
ppm 
mL/min (L/min) 
Enter the dilution gas flow to be actually set, within the range of measured values 1 to 4 of the dilution gas flow measured above, and also over the range between 200 and 8000 mL. If the dilution gas flow to be set is between 200 mL and 2000 mL, enter a value in 20 mL units. If it is between 2000 mL and 8000 mL, enter a value in 100 mL units.
Dilution gas flow to be set
(mL/min)
Diffusion tube for multiple components  Generated gas concentration  

First tube   
ppm 
Second tube   
ppm 
Third tube   
ppm 
Fourth tube   
ppm 
In the case where the same gas name was selected for multiple diffusion tubes, the generated gas concentration is a value equal to the total of the generated gas concentration for each diffusion tube.
Calculation of dilution gas flow
The dilution gas is calculated using the following equation:
F＝K×Dr×10^{3}C
 F：
 Flow of dilution gas (mL/min)
 C：
 Gas concentration for calibration gas （ppm）
 Dr：
 Diffusion rate （µg/min)
 K：
 Coefficient for converting the gas weight into volume (L/g)
K＝22.4M× 273+t273× 760P
 M：
 Molecular weight
 t：
 Temperature
 P：
 Pressure （mmHg）
Supplementary description of diffusion tubes for multiple components
 When using the measured diffusion rate indicated in the technical data, a more accurate value can be acquired by multiplying the attached I.D. measurement correction coefficient by each diffusion tube.
 The reference diffusion rate for the second and subsequent diffusion tubes is the diffusion rate calculated using the value of the dilution gas flow, based on the input conditions for the first diffusion tube. When entering the diffusion rate for the second and subsequent diffusion tubes, it is possible to generate the desired gas concentration by entering a numerical value that is as close as possible to this reference diffusion rate.
 Of the second and subsequent diffusion tubes, if there is no reference diffusion tube whose diffusion rate is near the reference diffusion rate, change the diffusion rate of the first diffusion tube to a different numerical value indicated in the technical data. Depending upon the particular numerical value, regarding the diffusion rate of the second and subsequent diffusion tubes, it is possible to select a numerical value that is near the reference diffusion rate.
Likewise, in the case where the gas name for the first diffusion tube is to be changed to a different gas to be generated, it is sometimes possible to enter a numerical value that is near the reference diffusion rate, regarding the second and subsequent diffusion tubes.  The ratio of the diffusion rate for each diffusion tube is as shown below.
Kind of diffusion tube D01 D02 D03 D04 D05 Diffusion rate comparison 1 Approx. 2.6 Approx. 6.2 Approx. 12.2 Approx. 23.4  When the set temperature is increased, the diffusion rate of each diffusion tube increases.
 Up to four diffusion tubes for multiple components can be used. Consequently, a mixed gas consisting of four components can be acquired simultaneously.
 By placing the same sample in multiple diffusion tubes, the concentration preparation range can be widened. The diffusion rate in this case is the sum of the diffusion rate of each diffusion tube.
 When the flow of the dilution gas is increased, the concentration of the generated gas decreases, and when the flow is reduced, the concentration of the generated gas increases. However, the ratio of the concentration generated from each diffusion tube does not change.
 When it is necessary to realize more accurate gas preparation, measure the diffusion rate under the actual conditions of use. Regarding the method of measuring the diffusion rate, refer to the instruction manual.

About gas detector tubes

General information on gas measurement

Reference