Tech Support

Using BetaCAP30 series gas dividers is very simple, but some care must be placed in some special cases.

When the two input gases (gas to be diluted and diluting gas) have different viscosities. This is not a frequent case : generally, with concentrations lower than few percents the mixture viscosity is very similar to the balance gas viscosity.       In the case you handle span gas concentrations higher than 1%, may be you should know the viscosity of such gas mixture (see the menu “Calculation sheets”) to evaluate if it may be required to take into consideration some correction.

Analyzing the formula          Dilution rate  = N / [N + (30 – N) x (P0/P1) x (η1/η0)]             Where N is the number of capillaries crossed by the span gas, P1 and η1 are the pressure and viscosity of the span gas and P2 and η2 are the pressure and viscosity of the diluting  gas, it’s evident that viscosities are compensated when  P1/P0 = η1/η0.

With the electronic pressures control, the s.p. of P1 is  set by the user to get the wanted gas output flow, but P0 is fully controlled by the electronics, so the wanted ratio may be automatically set, when the user submit the viscosities values, automatically calculated by the speadsheet you may find at the link

http://www.beta-strumentazione.it/Documents/Spreadsheets/ViscosityCalculation_ENG.xls

The more recent diluter BetaCAP60-3G makes internally the calculation of the test gases viscosity and provides the compensation in a fully automatic way.