Apparatus employing diode junction means for measuring subterranean temperatures

Claim 1

In apparatus for measuring temperature and change in temperature in a borehole penetrating subterranean formations by employing aboveground equipment; a downhole tool suspended on a cable within said borehole for movement along the longitudinal axis of said borehole; and depth measuring means for determining the depth of said tool in said borehole, the improvement comprising: a. diode junction means for measuring temperature, said diode junction means being disposed in said downhole tool and having a substantially linearly varying voltage drop at a constant current within the temperature range of 60*-350* F; b. a power supply means and a temperature-compensated constant current regulator means for maintaining a constant current flowing through said diode junction means regardless of variations in temperature along said borehole, said power supply means and said temperature-compensated constant current regulator means being serially connected in the forward biased direction with said diode junction means; said temperaturecompensated constant current regulator means comprising a field effect transistor serially connected via one lead with said diode junction means and via the other lead with a resistor means and a diode means for temperature compensation; the gate of said field effect transistor being connected with said other lead at the juncture of said power source and said serially connected diode means and resistor means; c. signal generating means for generating signals that are a function of the voltage present at the juncture of said diode junction means and said constant current regulator means, said signal generating means being connected with said diode junction means; d. transmitter means for transmitting said signals to the aboveground equipment, said transmitter means being connected with said signal generating means and with conductor means in said cable for effecting an electrically continuous path; e. converting means for effecting an analog indication of said temperature in response to said signals, said converting means being disposed in said above-ground equipment and connected via said conductor means with said transmitter means; f. differentiator means for differentiating said analog indication of temperature to effect an indication of temperature anomalies along the longitudinal axis of said borehole, said differentiator means being connected with said converting means; and g. recorder means for recording with respect to depth said analog indication of temperature and said indication of temperature anomalies, said recorder means being connected with said depth measuring means, with said converting means and with said differentiator means.