Looking at the diagram you see how different combinations of the solenoid valves EV1 ... EV5 realize the 30 possible dilution ratios. The solenoid valve EV6 has the purpose of providing a pause position (no flow) of the diluter. The electronic pressure control acts on the differential pressures between inlet and outlet: the pressure actually applied to the capilla-ries ends. The calibration of the sensors is of "static" type (no gas flow): the two inlets are closed by control valves, the solenoid valves do configure the dilution 15:30 to open ways connecting through capillaries the output with both inlets. Applying the reference pressure values at the output, the same value is read by all the three sensors and calibration is done. The sole purpose of the calibration is the balancing of the sensors (not individual measures): thus the value of the reference pressure applied is not critical (traceability is not required).