Digital temperature measuring apparatus with self-diagnostic function

Abstract

Abstract PURPOSE:To make a circuit simple and inexpensive, by using a time constant circuit containing a temp. measuring resistor, a monostable multivibrator and a measuring signal generating circuit in place of the use of an A/D converter. CONSTITUTION:A signal processing circuit 3A outputs a measuring start signal A to a monostable multivibrator 8 and a measuring signal generating circuit 9. The multivibrator 8 outputs a pulse signal B having a time width T proportional to the time constant of a time constant circuit by the rising of said signal A. The circuit 9 combines the wave form of the signal B outputted from the multivibrator 8 and that of the previous signal A to form a pulse time width measuring signal C. The signal C rises from an 'L' level to an 'H' level for the first time at the rising time of the signal B outputted from the multivibrator 8. A signal processing circuit 3A counts the time from the output time of the signal A to the input time of the signal C to measure a time width T and subsequently calculates temp. from the time width T on the basis of the resistance value-temp. characteristic of a temp. measuring resistor 1.

Inventors

• 👤 Yasuaki Kojima
• 👤 小島　康昭

Bibliographic Details