Temperature sensing circuit

• US 4,267,468 A
• Filed: 04/23/1979
• Issued: 05/12/1981
• Est. Priority Date: 04/23/1979
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hilliker, Stephen E.
• Primary Examiner(s): Miller, Jr., Stanley D.
• Assistant Examiner(s): Davis, B. P.
• Application Number:
  US06/032,031
• Time in Patent Office: 750 Days
• Field of Search: 307/310, 328/1, 328/3, 340/882, 323/75 H, 323/75 K, 73/262 AR
• US Class Current: 327/512
• CPC Class Codes: G01K 7/25 for modifying the output characteristic, e.g. linearising

Abstract

An improved temperature sensing circuit as disclosed in which the voltage drop across a thermistor is compared to the voltage drop across a capacitor to produce a linear output proportional to temperature.

Claims

1. In an electrical circuit for producing an output signal proportional to temperature and having four arms connected in a bridge configuration wherein a first arm comprises a non-linear temperature sensing element, a source of voltage is connected across one diagonal of said bridge, and a comparison means is connected across the other diagonal, the improvement comprising:

a second arm, not in series with said first arm, comprising capacitor means;

switch means in a third arm, in series with said second arm, for selectively charging said capacitor; and

said comparison means comprises voltage comparison means for producing an output signal indicative of the temperature of said sensing element.

2. The circuit as set forth in claim 2 wherein said second arm further comprises discharge means connected in parallel with said capacitor means.

3. The circuit as set forth in claim 2 wherein said discharge means is variable whereby said circuit can be calibrated.

4. The circuit as set forth in claim 2 wherein said discharge means comprises switch means for selectively discharging said capacitor.

5. The circuit as set forth in claim 4 wherein said switch means intermittently discharges said capacitor.