Patent ID: 7878703

Claim:
A unit of fire fighting equipment having a direct injection foam delivery system, comprising: a water pump for pumping water through a first pipe; a foam pump for pumping foam through a second pipe; a mixing chamber having a first input coupled for receiving the water and a second input coupled for receiving the foam and an output for producing a water and foam mixture; a control unit; a first conductivity sensor for monitoring conductivity of the water and foam mixture and providing a first electrical signal to the control unit; a second conductivity sensor for monitoring conductivity of the water and providing a second electrical signal to the control unit, wherein the control unit controls the foam pump in response to a difference between the first electrical signal and second electrical signal; a flow meter monitors flow rate of the water and provides a third electrical signal to the control unit which in turn controls the foam pump in response to the third electrical signal; and a temperature sensor monitors the water and provides a fourth electrical signal to the control unit wherein: the control unit controls the foam pump flow for changes in water conductivity resulting from changes in water temperature, and the control unit applies a correction factor to the flow meter to account for changes in water viscosity resulting from changes in water temperature.