JPH0131579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermometer using a crystal resonator.

Conventionally, a method of realizing a thermometer as shown in FIG. 1 using two crystal oscillators is known. Basic crystal oscillator and oscillation circuit 1 (for example, resonance frequency is 32K)
A signal 2 (Hz) is input to a frequency dividing circuit 3, and a signal 4 frequency-divided to an appropriate length is sent to a gate input of a counter 5. On the other hand, the crystal oscillator and oscillation circuit 6 of the temperature sensor used as the temperature sensor (for example, the resonance frequency is 100 KHz) has a higher resonance frequency than the reference crystal oscillator and oscillation circuit 1, and its output signal 7 is input to the counter 5. . Therefore, when the gate input of the counter 5 is at High level (or Low level), the frequency of the crystal resonator of the temperature sensor used as a temperature sensor and the frequency of the oscillation circuit 6 are counted by the counter 5. A timing chart showing this state is shown in FIG. This count value 8 includes temperature information. In other words, if the temperature change in the resonant frequency of the crystal oscillator of the temperature sensor and the oscillation circuit 6 is as shown in FIG. This will tell you the temperature at that time. Of course, the reference crystal oscillator and oscillation circuit 1 also have frequency dependence on temperature, but since the frequency is divided by the frequency divider circuit 3, the temperature dependence of the divided frequency is very small and can be almost ignored. becomes. The count value 8 of the counter 5 is stored in ROM (read-only memory).
9, and the output of the ROM 9 is input to the display 10 and displayed as temperature information. Of course ROM
Characteristics as shown in Figure 3 are written in 9.
When a frequency value is input, temperature data corresponding to the frequency value is output.

Using two crystal oscillators in this way makes it easy to create a thermometer, but when trying to incorporate this system into a small information device such as a wristwatch, having two crystal oscillators reduces energy consumption. This is a major constraint in terms of The present invention removes the above restrictions and
The aim is to provide technology that allows even book crystal oscillators to be installed in small information devices such as wristwatches.

A detailed explanation of the invention is given below using figures.
An embodiment of the invention is shown in FIG. Items 1 to 10 in the figure are the same as those in FIG. 1, so their explanation will be omitted. The voltages applied to the crystal resonator and the oscillation circuits 1 and 6 are switched by a switch 11 to either a low voltage circuit 12 or a battery voltage 13. An oscillation circuit including a crystal resonator has a characteristic of having an oscillation start voltage and an oscillation stop voltage. In other words, the crystal resonator will not start oscillating unless the voltage is above a certain level.
The voltage that starts this oscillation is called the oscillation start voltage. Furthermore, when the voltage falls below a certain level, the crystal resonator stops oscillating. The voltage that stops this oscillation is called the oscillation stop voltage. Normally, the oscillation start voltage is higher than the oscillation stop voltage. For example, battery voltage
1.57 (V), the output voltage of low voltage circuit 12 is 1.2 (V)
If so, the oscillation start voltage and oscillation stop voltage of the reference crystal resonator and the oscillation circuit 1 should be set to the output voltage of the low voltage circuit 1.2 (V) or less. On the other hand, the oscillation start voltage and oscillation stop voltage of the crystal resonator of the temperature sensor and the oscillation circuit 6 are set to the output voltage of the low voltage circuit 12.
Keep it larger than 1.2 (V) and smaller than the battery voltage 1.57 (V). In this way, if the switch 11 is tilted to the low voltage circuit side, the reference crystal oscillator and oscillation circuit 1 are oscillating, but the temperature sensor crystal oscillator and oscillation circuit 6 are not oscillating, and the temperature is Not measured. Furthermore, in this state, the crystal resonator of the temperature sensor and the oscillation circuit 6 are not oscillating, so there is no energy consumption here. On the other hand, if the switch 11 falls to the battery voltage 13 side, the crystal resonator of the temperature sensor and the oscillation circuit 6 also start oscillating, making it possible to measure the temperature. That is, when the temperature is not being measured, the switch 11 is moved to the low voltage circuit 12 side to stop the oscillation of the temperature sensor's crystal oscillator and oscillation circuit 6, thereby reducing energy consumption in the temperature sensor's crystal oscillator and oscillation circuit 6. lose. At that time, the display may display the current time using the reference crystal oscillator and the oscillation circuit 1. On the other hand, when measuring the temperature, the switch 11 is turned to the battery voltage 13 side, the crystal oscillator of the temperature sensor and the oscillation circuit 6 start oscillating, and the display 10 displays the current temperature.

As described above, according to the present invention, by changing the oscillation start voltage and oscillation stop voltage of the oscillation circuits of the two crystal oscillators and providing a low voltage circuit, energy consumption can be reduced during non-temperature measurement. It becomes possible to mount a thermometer on information equipment.

[Brief explanation of drawings]

Figure 1 shows a conventionally known temperature measurement circuit. Second
The figure is a timing chart of the circuit shown in Figure 1. Figure 3 shows the frequency-temperature characteristics of a crystal resonator used as a temperature sensor. FIG. 4 is a circuit diagram of the present invention. 1...Reference crystal oscillator and oscillation circuit, 2...Crystal oscillator of temperature sensor and oscillation circuit, 12...Low voltage circuit, 13...Battery.

Claims (1)

[Claims] 1. In a thermometer that measures temperature using a reference crystal oscillator and a temperature sensor crystal oscillator,
The oscillation start voltage and oscillation stop voltage of the oscillation circuit including the reference crystal resonator are made smaller than the oscillation start voltage and oscillation stop voltage of the oscillation circuit including the temperature sensor crystal resonator, and the power supply is applied to both of the oscillation circuits. consists of a low voltage source and a high voltage source, and the oscillation start voltage and oscillation stop voltage of the oscillation circuit including the reference crystal resonator are set to be lower than the output voltage of the low voltage source,
The oscillation stop voltage of the oscillation circuit including the crystal resonator for the temperature sensor is set to be higher than the voltage of the low voltage source and lower than the voltage of the high voltage source, and the two voltage sources are switched to both oscillators. A thermometer characterized by being equipped with a changeover switch for connection.