The standard Model 146i hardware/plumbing configuration comprises gas
and zero air flow controllers, as shown in Figure 1–1. The basic unit can
handle three gas standards, controlled by individual solenoids (a six-gas
option is also available). The zero air flow and the gas flow are regulated by
mass flow controllers. The zero air controller is high flow (typically 10 slm
full scale). The gas flow controller is low flow (typically 100 sccm). A
Teflon mixing chamber is used to achieve complete mixing of the two
components at the desired concentration level. This hardware/plumbing
configuration allows precision gas dilution.