JPS58214823A - Temperature measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the displaying of a linearized temperature by reading out and indicating temperature data corresponding to a digital signal. CONSTITUTION:The relationship of output voltage of a thermistor and temperature data in determined by measurement or calculation and the temperature data is memorized into memories IC 5 and 6 corresponding to the output voltage. The temperature data from data terminals 5D and 6D of the IC 5 and 6 is inputted into BCD-7 segment conversion section 7-9 digit by digit to drive numerical displays 10-12 for displaying data for the first, second and third digit separately whereby the temperature data is displayed in digital number.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention converts temperature changes into resistance changes using, for example, a thermistor, side temperature resistor, or thermocouple.

The present invention relates to a temperature measuring device that measures temperature by measuring this resistance value.

Conventionally, temperature has been measured using a thermistor, resistance temperature detector, or thermocouple that converts temperature changes into resistance changes. However, since the resistance change of these elements is not linear with respect to temperature change, some type of linear rice function was required to improve measurement accuracy and to use them over a wide temperature range. For example, if we take a thermistor as an example of a device with the most dramatic resistance change, the thermistor exhibits a temperature-resistance change as shown in FIG.

In Figure 1, the horizontal axis is temperature! , the vertical axis is the resistance value R. If the change characteristics shown in Figure 1 remain as they are, the temperature cannot be directly read from the resistance value.

In order to do this, a circuit as shown in Figure 2 is often constructed. / in the figure is a thermistor, and the resistance -
This is further connected in series with the resistor 3 and connected between the power source and ground of one circuit. Then, the voltage V between the ground and the terminal is taken out as an output.

This output voltage ■ shows a change as shown in FIG. 3 with respect to temperature. That is, if the horizontal axis is the temperature T and the vertical axis is the voltage V, the output voltage decreases almost linearly as the temperature rises. If resistance 2 and J are selected appropriately, this graph can be made almost straight.

However, when widening the measurement temperature range or requiring highly accurate temperature measurement, characteristics that are even closer to a straight line are required, and for these purposes linearization circuits and devices called beams are used. is necessary. However, such circuits and devices use a large number of precision resistors, variable resistors, or operational amplifiers, making adjustment complicated and expensive.

The purpose of this was to eliminate the drawbacks of such conventional devices and circuits.The output voltage V of the thermistor circuit is converted into a digital signal by an analog-to-digital conversion circuit, and that signal is written in advance in a memory such as a ROMIC. There is. It is an object of the present invention to provide a temperature measuring device capable of displaying a specially adjusted temperature by reading out temperature data corresponding to the digital signal and displaying it on a display, without requiring a special calibrator or the like.

Hereinafter, one embodiment of the present invention will be described based on the block diagram shown in FIG. In the figure, the symbols / to 3 are the same as those shown in FIG. 1. DA is an analog-to-digital converter (hereinafter referred to as A/P converter), which inputs the output voltage of the thermistor circuit and converts it into a digital signal. ! and 6 is a memo IJIC and consists of a ROMIC that will not cause data to be lost even if the power goes out. These include chip select signal terminals ja and 6a, read signal terminals b and 6b, etc., which are kept in the active state so that they can be read at all times.Then, the address terminals C and 6c are connected to the A/D conversion Connect the external power signal and access the memory directly.

Memory IC! For example, if a 2-kilobyte one is used, the address signal will have a 1/bit configuration of A o - A 10, so the output signal of the A/D converter will also be 1/bit.
Any bit configuration is sufficient. Of course, if only one kilobyte of the memory of the memory IJIC is not used, the output signal of the A/D converter may have /θ bits. Memo+7 IC and 6 have a data configuration of 00% p7 and a g focus configuration.

When using this t bit as a BCD signal, the BCD
It is possible to configure a BOD of only 7 digits of signals, and by using two τ memory ICs, it is possible to configure a BOD of 5 or more digits.

In this example, the memo IJ I C! The case is shown in which the BOD is configured with 5 digits using 5 and 6 pieces.

Memo' J I C! Temperature data corresponding to the digital output signal of the A/D converter q is written in advance in the address corresponding to the digital output signal of the A/D converter q as the stored contents of the memory.

That is, 1. For example, find the relationship between the output voltage and temperature data of the thermistor circuit shown in the graph of FIG. put. In FIG. 5, for example, A20 on the graph is a point at 0° C., and the output voltage at this time is YO■.

Also, point 21 is a point at 30°C, and the output voltage at this time is ll
It is v. Similarly, point 2 is a point at -30° C., and the output voltage at this time is 2.2V. Although the graph is not a straight line, a fixed curve can be obtained by determining the values of the series resistance 3 and the parallel resistance 2.

Therefore, the output voltage in λmV increments or! Calculate the temperature value corresponding to each V step. Next, calculate the temperature value corresponding to the address in the memory corresponding to this output voltage.
CD, if you write it in 7 digits.

With the above configuration, temperature data corresponding to the pressure voltage of the thermistor can be obtained from the memory IC and the 3-digit ECD code. This humidity data is stored in memory IC5,A
It is output from data terminals 5d and 6d. This temperature data is converted into a PC for each digit by a 7-segment converter 7. To,
A numeric display 10 for displaying the data of the third digit and the third digit. // and /2 are driven to display hot water supply level data in digital numbers.

In the above embodiment, the output voltage was set in 2 mV or 5 mV increments, but it is possible to increase the capacity of the memory IC. If you change the scale of the rilt's output voltage to smaller increments, such as 1/mV, and store the corresponding 9 temperatures, you can make it even more accurate. If this is done, even higher precision can be achieved. Furthermore, if a multiplexer and its driving circuit are provided at the input, a large number of temperature sensors can be connected.Also, in this embodiment, a thermistor has been described.

It can also be applied to cases where a thermocouple or a resistance thermometer is used as a temperature sensor. Furthermore, if it is incorporated into equipment that uses an arithmetic processing unit such as a microcomputer, there is an advantage that the memory of the microcomputer can be used. Furthermore, if a target temperature setting means and a temperature comparison means are added, the present invention can be used as a temperature controller or an alarm, and the scope of application of the present invention is wide-ranging.

As described above, according to the configuration of the present invention, highly accurate measured values can be obtained over a wide temperature range despite the fact that the temperature sensor has nonlinearity.

Moreover, it does not require complicated circuits like conventional devices.

This has the advantage that it can be realized with a simple configuration and at a very low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the temperature-resistance characteristics of a general thermistor, and FIG. 2 is a circuit diagram showing an example of a general linearization circuit for linearizing the characteristics of the thermistor. FIG. 3 is a diagram showing the hot water temperature-resistance characteristics of the circuit shown in FIG. 2. FIG. 1 is a block diagram showing a temperature measuring device according to an embodiment of the present invention, and FIG. 5 is a diagram for explaining the operation of FIG. 1. In the figure, l is a thermistor, 2 is a parallel resistance,
3 is a series resistor, q is an A/D converter, ! and t are memory ICs, RIa and 6a are chip select signal terminals of each IC, RIb and Ab are read signal terminals of each IC, RIC and...6c are address signal terminals of each IC, jd and 6CL is the data signal terminal of each XC, 7
゜g and 9 are 1 digit, 2 digit and 3 digit BCD respectively
-7 segment converter, 10. // and / are i/digit, 2-digit, and 3-digit numeric indicators, respectively. In addition, in FIG. 1, the same reference numerals indicate the same or corresponding parts. Agent Shin Kuzuno - Figure 2

Claims (1)

[Claims] (1) A temperature detection means that extracts a signal corresponding to the temperature, an A/D conversion section that converts the signal into a digital signal, and a storage section that stores temperature data corresponding to the output of this A/D conversion section. , means for reading out corresponding temperature data from the storage unit based on the output of the A/D conversion unit, and displaying the data numerically. (j) The temperature measuring device according to claim 1, wherein the temperature detecting means comprises a thermistor, a parallel resistor, and a series resistor.藺 The temperature measuring device O according to claim 1 or 2, wherein the storage section is constituted by ROMI C.