Design and tests of the high-precision temperature control and measurement system in the digital gravimeter

The high-precision digital gravimeter is widely used in mineral resources exploration. The gravity sensor composed of quartz elastic system, the core part of this instrument, is very sensitive to the ambient temperature. The change of gravity caused by the change of ambient temperature is much greater than the accuracy of the instrument proper, while such a property varies with different instruments. If the thermostatic environment of the gravity sensor is not guaranteed, or the weak change of the ambient temperature cannot be accurately measured and compensated, the measurement accuracy and consistency of the gravimeter will be seriously affected. To solve this problem, this work studies the design method and key technology of high precision temperature control and measurement system in this instrument. Considering the characteristics of the digital gravimeter such as high precision, small volume, low power consumption and portable manner, this work makes an exhaustive analysis on the key device selection, thermal structure, circuit and software in the high-precision temperature control and measurement system, and gives specific solutions. Tests on three aspects, i.e. static operation, high and low temperature conditions, and the temperature coefficient of the quartz elastic system, are conducted to verify the performance of this system. The results show that this high-precision temperature measurement system reaches the resolution of 10 mu degrees C; its temperature changes by 70 mu degrees C in the constant temperature and less than 1 m degrees C in the ambient temperature range -20 degrees C to +45 degrees C; and accurate determination of quartz elastic system's temperature coefficient can be achieved by the temperature controlled trimming device. This study provides an effective solution to eliminate the influence of environmental temperature change in the development of high-precision gravity measurement instruments.