TEMPERATURE COMPENSATING DIGITAL SYSTEM FOR ELECTROMECHANICAL RESONATORS

• US 3,719,838 A
• Filed: 08/02/1971
• Issued: 03/06/1973
• Est. Priority Date: 08/02/1971
• Status: Expired due to Term

• Current Assignee: Jan Willem L. Prak, Ralph Peduto
• Original Assignee: Jan Willem L. Prak, Ralph Peduto
• Inventors: Prak, Jan Willem L., Peduto, Ralph
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Budd, Mark O.
• Application Number:
  US05/168,136
• Time in Patent Office: 582 Days
• Field of Search: 310/8,8.1 334/15 331/116R,176
• US Class Current: 310/315
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence

Abstract

A temperature-compensating system for piezoelectric crystal oscillators and other electromechanical resonators whose operating frequency varies as a function of ambient temperature. The system includes a temperature transducer for producing an analog measuring signal as a function of temperature within the temperature range of interest, which analog signal is converted into a corresponding binary number. The number is applied as an input to a logical function generator programmed to produce for each input number, an output binary number whose value depends on the generated function. The output number is converted to an analog control signal which is applied to a responsive element coupled to the resonator to vary the operating frequency thereof. The arrangement is such that the curve of the frequency shift due to the analog control signal, inversely matches the frequencytemperature curve of the resonator to effect exact frequency compensation therefor.

Claims

1. A temperature-compensating system for an electromechanical resonator whose operating frequency depends on ambient temperature, said system comprising:

A. sensor means to produce an analog measuring signal as a function of changes in said ambient temperature, B. an analog-to-digital converter coupled to said sensor means to convert said measuring signal to a corresponding digital value, C. a logical function generator constituted by a programmable read only memory, D. means to apply said digital value as an input to said generator to produce an output digital value, said generator function being programmed to the frequency-temperature characteristic curve of said resonator to provide an inverse match therefor, E. means in circuit with said resonator to effect a shift in the operating frequency thereof, and F. means to apply said output value to said frequency shift means to effect a shift in said operating frequency in a direction and to an extent compensating for the effect of ambient temperature thereon.

2. A system as set forth in claim 1, wherein said resonator is a piezoelectric crystal.

3. A system as set forth in claim 1, wherein said resonator is a tuning fork.

4. A system as set forth in claim 1, wherein said sensor means is constituted by a thermistor network.

5. A system as set forth in claim 1, wherein said sensor means is constituted by a temperature-sensitive capacitor.

6. A system as set forth in claim 1, wherein said sensor means is constituted by a temperature-sensitive diode.

7. A system as set forth in claim 1, wherein said analog-to-digital converter is adapted to produce a binary number whose value corresponds to the applied analog signal.

8. A system as set forth in claim 2, wherein said means in circuit with said crystal is a voltage-responsive capacitance diode.

9. A system as set forth in claim 2, wherein said means in circuit with said crystal is a capacitor network.

10. A system as set forth in claim 2, wherein said means in circuit with said crystal is a resistor network.

11. A system as set forth in claim 8, wherein said means to apply said output value to said voltage-responsive capacitance diode is constituted by a digital-to-analog converter coupled to said frequency generator to produce an analog control voltage which is applied to said diode.

12. A temperature-compensating system for an electromechanical resonator whose operating frequency depends on ambient temperature, said system comprising:

A. sensor means to produce an analog measuring signal as a function of changes in said ambient temperature, B. an analog-to-digital converter coupled to said sensor means to convert said measuring signal to a corresponding digital value, C. a logical function generator, D. means to apply said digital valuE as an input to said generator to produce an output digital value, said generator function being related to the frequency-temperature characteristic curve of said resonator to provide an inverse match therefor, E. a presettable frequency divider, F. means to apply the output of said resonator to said divider to produce a relatively low frequency output signal, and G. means to apply said output digital value from said function generator to the preset inputs of said divider to compensate said output signal for changes in temperature.

13. A system as set forth in claim 12, further including means to electronically add said output digital value to an external preset number to produce a sum value which is applied to the preset inputs of said divider.