JPH0124600Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Field of the invention The present invention relates to an improvement of an electronic thermometer that operates on battery power and digitally displays the measured temperature.

(b) Background of the invention Conventionally, electronic thermometers of this type have had the disadvantage that they tend to malfunction when the battery voltage drops. In addition, as a countermeasure to this, devices equipped with a battery voltage drop detection circuit have a large proportion of power consumption in this voltage drop detection circuit to the overall power consumption.
This has the disadvantage of accelerating the drop in battery voltage.

(c) Purpose of the invention In view of the above-mentioned problems, the present invention detects a voltage drop with the minimum necessary power consumption by using the voltage drop detection circuit at two points: when the measurement start switch is turned on and when the measurement ends. Moreover, the purpose is to provide a highly reliable electronic thermometer.

(d) Structure of the invention FIG. 1 shows an embodiment of the electronic thermometer of the invention, in which a temperature detection circuit 1 A/D converts the output of a temperature sensor 2 made of a temperature-sensitive resistor and displays a digital display part 3.
The measurement operation is started when the measurement start switch 4 is turned on. In this embodiment, a clock oscillator 5 is activated when the measurement start switch 4 is turned on, and the presence or absence of this clock determines whether or not the entire apparatus operates. Further, the differential circuit provided in the temperature detection circuit 1 generates a measurement end pulse signal when the temperature rise becomes gradual, thereby terminating the temperature measurement operation. The above operation start pulse signal P
1 and measurement end pulse signal P2 are temperature detection circuit 1
The battery voltage drop detection circuit 7 is operated for a certain period of time by the output P3 of the OR circuit 6 which receives both signals P1 and P2 as inputs.

FIG. 2 shows an example of the battery voltage drop detection circuit 7, in which the output P3 of the OR circuit 6 is applied to the one-shot circuits M1 and M2, and the output of the one-shot circuit M1 is applied to the analog switches 8 and 9.
added to the gate. Both analog switches 8 and 9 are inserted into a bridge circuit formed by resistors R1, R2, R3 and a diode D1 as shown in the figure, and the outputs of the bridge circuit, that is, the potentials at points a and b are compared by a voltage comparator 10. . The output of this voltage comparator 10 is applied as a voltage drop detection signal to the latch circuit FF, and the one shot circuit M
The signal is latched into the latch circuit FF by the output signal No. 2. The output of the latch circuit FF is applied to the digital display section 3 via the temperature detection circuit 1 and displayed.

FIG. 3 is a waveform diagram showing the operation of the battery voltage drop detection circuit 7, and FIG. 4 is a diagram explaining its principle. In FIG. 3, P3 is an output pulse of the OR circuit 6, and upon arrival of this pulse P3, a pulse signal of a predetermined pulse width is output from the one-shot circuits M1 and M2. FIG. 4 shows how the battery voltage E changes over time and how the potential at points a and b in FIG. 2 changes as the voltage E changes. and 9 are opened, voltages as shown in FIG. It latches. In FIG. 3, a potential obtained by dividing the battery voltage E by resistors R1 and R2 appears at point a,
Since a constant voltage drop due to the diode D1 appears at point b, the value of the battery voltage E at which the output of the voltage comparator 10 is inverted can be appropriately set by adjusting the ratio of the resistors R1 and R2. For example, on the left side of t1 in FIG. 4, it is detected that the battery voltage E has decreased below the set value, and this information is displayed on the display section 3.

(e) Effects of the invention According to the invention, as mentioned above, a pulse signal is output from the temperature detection circuit when the measurement start switch is turned on and at the end of measurement, and the battery voltage drop detection circuit outputs a pulse signal for a certain period of time after receiving this pulse signal. Since the system detects voltage only once and outputs the resulting information to the display, it consumes much less power and saves battery life compared to the conventional method that constantly detects voltage during body temperature measurement. It has the advantage of being able to last a long time, and since the battery voltage is detected at two points, at the start of measurement and at the end of measurement, it has the advantage of having the same reliability as conventional methods that constantly perform detection operations. be.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention, FIG. 2 is a specific circuit diagram of the main parts of the same, FIG. 3 is a waveform diagram of each part of the same, and FIG. 4 is a diagram of the principle of operation of the same. 1 is a temperature detection circuit, 2 is a temperature sensor, 3 is a digital display section, 4 is a measurement start switch, 5 is a clock oscillator, 6 is an OR circuit, and 7 is a battery voltage drop detection circuit.

Claims (1)

[Scope of utility model registration request] The operation of the temperature detection circuit, which displays the output of the temperature sensor on the display, is started by operating the measurement start switch, and the measurement is ended when the temperature rises gradually, and the battery voltage decreases. In an electronic thermometer equipped with a detection circuit, there is provided a means for outputting a pulse signal when the temperature detection circuit starts operating and ends measurement; An electronic thermometer provided with a switch means for activating a drop detection circuit.