JPS58205829A - Electronic thermometer - Google Patents

Abstract

PURPOSE:To reduce the power consumption by extending the sampling cycle for detecting temperature when the temperature variation is limited. CONSTITUTION:After latched 3 following an A/D conversion 2, output of a temperature sensor 1 is converted to a temperature value with a conversion ROM5 and displayed 7 via a decoder/driver 6. The temperature data previously measured is stored in a latch 4 and as the difference increases between the two temperature values, the output of a clock selector 10 is turned to 1min sampling cycle while as it decreases, the output thereof 10-2min sampling cycle. Thus, the sampling cycle of the temperature sensor 1, an A/D converter 2 and the latch 3 is determined by the output of a clock selector 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic thermometer, and more particularly to a variable sampling period electronic thermometer.

Electronic thermometers have the advantage of easy-to-read displays and relatively flexible shapes, and are used not only as stand-alone thermometers but also incorporated into other devices. They are also used as temperature and temperature gauges, and are incorporated into table clocks, electrical appliances, and many other furniture items. However, when thermometers are operated during the day, their power consumption becomes a problem, and efforts continue to be made to reduce power consumption. In thermometers, the part that handles analog signals consumes a lot of power;
1. Due to the improvement and development of liquid crystal display devices, the power consumption in the logic circuit and subsequent parts is becoming much smaller. In order to reduce power consumption, the part t that handles analog signals is generally operated only for a short time at certain regular intervals. That is, the temperature is detected and displayed at a constant sampling period. In order to further reduce power consumption, it is possible to lengthen the sampling period, but this has the disadvantage that if the temperature changes rapidly, it cannot keep up with the changes, resulting in large changes in the display temperature.

An object of the present invention is to eliminate such drawbacks and provide a thermometer with lower power consumption. This will be explained below with reference to the attached drawings.

The drawing is a block diagram of an embodiment of the invention. A clock serving as a reference for thermometer operation is first generated by an oscillator 8, and then frequency-divided by a frequency divider circuit 9 to obtain the necessary sampling synchronization. There are two frequency-divided clocks, one of which is selected by the next clock selector 10 to determine the sampling period.

In this sampling period, the output of temperature sensor 1 is A of the next stage.
The D converter 2 converts it into logical data. Previously measured temperature data is stored in the latch 3, and that data is first transferred to the latch 4, and then new temperature data is read into the latch 3. The temperature data of latch 3 is stored in conversion ROM 5.
The temperature value is converted into a corresponding temperature value and displayed on the display 7 via the decoder/drive-6. The absolute value of the difference between the temperature data of the latch 3 and the previous temperature data transferred to the latch 4 is taken by the difference circuit [2] and becomes one input of the comparator 13. The latch 14 has the output of the previous comparator 13,
In other words, data corresponding to the previous sampling period, which is the time from the previous temperature detection to the current temperature detection, is stored, and based on this data, a value in the comparison ROM 15 set in advance is selected and compared. It becomes the remaining input of the device 13. Difference times l! Compare 12 outputs ROM
15, the output of comparator 13 is determined based on the result, a clock is selected by clock selector 10, and the next sampling period is determined. The timing pulse circuit 11 includes a temperature sensor 1 and an ADK converter 2.
In addition to operating for a fixed short period of time at a selected sampling period, the timing of reading the latch 3, latch 4, and latch 14 is determined.

Normally it is 2 minutes, but when the measured temperature difference is 2 degrees Celsius or more from the previous time, the sampling synchronization changes to 1 minute. In normal cases with little temperature change, temperature data equivalent to 2 degrees Celsius is output from comparison ROM 15. and compared with measured temperature difference data. If a difference of 3°C occurs in the measured temperatures, the output of the comparator 13 will be inverted, and the output clock from the clock selector 10 will change to correspond to a sampling period of 1 minute, and the comparator R
OM15 outputs temperature data equivalent to 1℃,
The temperature difference that will be the standard for the next comparison will be 1'c.

When the temperature change becomes small, the output of the comparator 13 is inverted again and the sampling period returns to 2 minutes.

The present invention can reduce power consumption by lengthening the sampling period when temperature changes are small, which satisfies today's demands for low power consumption), and this effect is remarkable in battery-powered thermometers. It is something. In addition, in principle, the sampling period can be set exactly as desired, and the temperature difference used as the standard for comparison can be set arbitrarily, so there is no unnaturalness such as sudden changes in the displayed temperature (and the effect is It is very large to use.

[Brief explanation of drawings]

5- The drawing shows a block diagram of an embodiment of the invention. 10. temperature sensor, 2. , AD converter, 3. . Latch, 40. Latch, 51. Conversion ROM, (3°, decoder/driver, 701 display, 8°, oscillator,
9.0 frequency divider circuit, 10. , Sunset selector, 11.
, timing pulse circuit %12. ．． Differential circuit, 130.
Comparator, 140. Latch, 150. Comparison ROM Above 6-

Claims (1)

[Claims] In a temperature sensor that consumes a large amount of power and in an electronic thermometer that operates a peripheral circuit of the temperature sensor intermittently, there is provided a means for storing a value regarding the measured temperature, a means for storing a value regarding the previously measured temperature, and a means for storing a value regarding the previously measured temperature. means for detecting the absolute value of the difference between the values, means for storing the previous sampling period, means for selecting a value related to the temperature preset by the previous sampling period, and the absolute value of the difference between the values related to the temperature. and a comparator for comparing the output from the means for selecting a value related to a preset temperature according to the previous sampling period, and means for selecting a different sampling period for the comparator. An electronic thermometer characterized in that the next sampling cycle is determined based on the change between the previous temperature and the previous sampling cycle.