Implantable-ingestible-electronic-thermometer

Description: This oscillator circuit features a quartz crystal with a nominal resonant frequency of 262,144 Hz, which is cut in an orientation that provides a significant linear coefficient of frequency variation with temperature. In this configuration, the oscillation frequency is primarily controlled by the crystal, provided that the gain-bandwidth product is at least four times the frequency. The selected component values in this circuit yield a gain-bandwidth product of 1 MHz. Additionally, the inductor L1 can be minimized to 100 to 200 turns with a diameter of 0.18 inches (4.8 mm) and a length of 0.5 inches (12.7 mm). While the schematic depicts two transistors in parallel, a single transistor may be employed to reduce power consumption, or three transistors may be used to enhance the output. This general oscillator circuit is capable of measuring temperatures ranging from -10 to +140°C. A variant designed for operation within the human body, specifically between 30 to 40°C, functions at a frequency of 262,144 ±50 Hz, exhibiting a frequency stability of 0.1 Hz and a temperature coefficient of 9 Hz/°C.

The oscillator circuit described utilizes a quartz crystal as the primary frequency-determining element, which is known for its excellent frequency stability and temperature characteristics. The crystal's orientation is crucial as it influences the temperature coefficient, allowing for predictable frequency variations with changes in temperature, making it suitable for precise applications such as temperature measurement.

The gain-bandwidth product of 1 MHz indicates that the circuit is designed to operate efficiently at the specified resonant frequency. The inductor L1, with its compact dimensions of 100 to 200 turns, is a critical component that aids in establishing the necessary oscillation conditions. The choice of a small inductor also contributes to reducing the overall size of the circuit, which is beneficial for applications requiring compact designs.

The configuration of transistors in parallel allows for flexibility in power management. The option to use a single transistor can lead to lower power consumption, which is advantageous in battery-operated devices. Conversely, utilizing multiple transistors can increase the output drive capability, making the circuit adaptable for various output requirements.

The temperature measurement capability of this oscillator circuit is noteworthy, allowing it to function effectively over a wide temperature range. The specific design for human body temperature monitoring demonstrates its application in biomedical fields, where precise temperature readings are critical. The specified frequency stability and temperature coefficient further enhance the circuit's reliability in such sensitive applications, ensuring that it remains accurate across the defined temperature range.

Overall, this oscillator circuit exemplifies a well-engineered solution for applications requiring precise frequency generation and temperature measurement, combining the advantages of quartz crystal stability with efficient circuit design.This oscillator circuit includes a quartz crystal that has a nominal resonant frequency of 262,144 Hz and is cut in the orientation that gives a large linear coefficient of frequency variation with the temperature. In this type of circuit, the oscillation frequency is controlled primarily by the crystal-as long as the gainbandwidth product is at least four times the frequency.

In this case, the chosen component values yield a gain-bandwidth product of 1 MHz. Inductor Ll can be made very small: 100 to 200 turns with a diameter of 0.18 in. (4.8 mm) and a length of 0.5 in. (12. 7 mm). Although the figure shows two transistors in parallel, one could be used to reduce power consumption or three could be used to boost the output. The general oscillator circuit can be used to measure temperatures from -10 to + 140°C. A unit made for use in the human body from about 30 to 40°C operates at 262,144 ±50 Hz with a frequency stability of 0.1 Hz and a temperature coefficient of 9 Hz/°C.