Measuring and testing – Volume or rate of flow – Thermal type
Patent
1982-10-13
1984-05-29
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Thermal type
731181, G01F 168
Patent
active
044507194
ABSTRACT:
In a thermal type air flow meter, a temperature-dependent resistor for sensing the flow rate of air is placed in the flow of air to be measured, and another resistor for detecting a current flowing through the above resistor is connected in series therewith. The current is controlled so that the temperature-dependent resistor is kept at a predetermined temperature which is higher than surrounding temperature by, for example, 150.degree. C. The resistance of the temperature-dependent resistor varies in accordance with the flow rate of air. However, since the current is controlled so that the temperature-dependent resistor is maintained at the predetermined temperature, the current varies with the flow rate of air. Accordingly, the speed of air can be obtained by measuring the current. In such an air flow meter, when a key switch of an engine is turned on to put a power supply to work, a short circuit is formed between both ends of the current detecting resistor to cause a large current to flow through the temperature-dependent resistor. Accordingly, the flow rate of air can be measured immediately after the power supply has been turned on.
REFERENCES:
patent: 4297881 (1981-11-01), Sasayama et al.
patent: 4338814 (1982-07-01), Romann
patent: 4341114 (1982-07-01), Plapp
Nishimura Yutaka
Ohyama Yoshishige
Sugiura Noboru
Goldstein Herbert
Hitachi , Ltd.
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