Self-compensating ovenized clock adapted for wellbore applications

A well logging instrument comprising:

• a sensor adapted to measure at least one of a drilling parameter and a formation characteristic;
• and
• at least one of a telemetry system and a storage device operatively coupled to the sensor, the telemetry system or the storage device operatively coupled to a clock system, the clock system comprising a dual mode oscillator crystal having a first output having a frequency related to a temperature of the oscillator crystal and a second output having a frequency substantially stable with respect to temperature, a temperature maintenance device, the temperature maintenance device and the oscillator crystal disposed in a thermally insulated chamber, and a processor operatively coupled to the temperature maintenance device and the oscillator crystal, the processor adapted to operate the temperature maintenance device so as to maintain a temperature of the chamber within a predetermined range, the processor adapted to calculate a substantially constant frequency clock signal from the second output and from a ratio of the frequency of the first output with respect to the frequency of the second output.