CONTROLLER FOR HOT WIRE TYPE AIR FLOWMETER

Title:

CONTROLLER FOR HOT WIRE TYPE AIR FLOWMETER

Document Type and Number:

Japanese Patent JPS6371619

Kind Code:

A

Abstract:

PURPOSE:To hold a hot wire clean all the time and to contrive to prolong its life without spoling the reliability by supplying a large current to the hot wire when a run time or run distance reaches a set value during a run and burning out foreign matter sticking on the hot wire. CONSTITUTION:For example, a run time counter 35 reaches its set value, its output signal is inputted to an OR circuit 38, which inputs a burning-out signal to driving circuit 34. Consequently, this circuit 34 supplied a driving pulse to the base of a transistor T1 connected between connection points D and B of bridge circuit 30 to turn on the T. Consequently, the bridge circuit 30 enters an unbalanced state and a current flowing to a register R3 decreases, so that the base current of the transistor T2 of a current control circuit 31 decreases. Consequently, the collector-emitter voltage VCE of a transistor T3 rises and a current flowing to a resistance R5 decreases. Further, a current from a constant voltage VB increases in the bridge circuit 30 to the contrary and the hot wire RH reaches high temperature to burn not the sticking matter.

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