JPH03215723A - Temperature detector - Google Patents

Abstract

PURPOSE:To accurately decide a grounding without reference to detected temperature by using a voltage which is applied to the series connection body of a thermistor and a resistance as a detection voltage. CONSTITUTION:The voltage of a DC power source 6 is divided with the resistance value of a resistance 7 in addition to the resistance value of a resistance 3 and the resistance value of the thermistor 1 and the temperature is detected in the form of the voltage at a point P. The voltage at the point P rises by the voltage applied to the resistance 7 in addition to the voltage applied to the thermistor 1. The detected voltage at the point P is digitized by an A/D converter 4 and compared by an arithmetic means 5 with a grounding decision threshold value, so that the voltage is converted into temperature data. Consequently, when the grounding is decided, the grounding of the thermistor can accurately be decided without being affected by noise nor the accuracy of the A/D converter 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a temperature detection device that uses a thermistor to detect temperature as a partial pressure, and determines whether the thermistor is grounded based on this detection level. [Prior Art] Fig. 3 shows the configuration of a conventional temperature detection device, in which 1 is a thermistor having a negative temperature coefficient whose resistance value decreases as the temperature increases, and 2 is a signal processing unit. , a resistor 3 connected in series to the thermistor 1 at point P, an analog/digital converter (hereinafter abbreviated as A/D converter) 4 that converts the analog input voltage at point P into a digital value,
It is comprised of a calculation means 5 that obtains temperature data based on the digital value or detects a ground fault in the thermistor 1, and a DC power supply 6. The DC power supply 6 has its H-pole terminal grounded and its (T)-pole terminal connected to the opposite end of the resistor 3 to the P point. Also, the end of the thermistor 1 opposite to point P is grounded. The A/D converter 4 and the calculation means 5 are connected to receive power from a DC power source 6. Next, we will explain the operation. The voltage of the DC power supply 6 is divided by the resistance value of the resistor 3 and the resistance value of the thermistor 1, and the temperature is detected as the voltage at point P. The voltage at point P, which is inversely proportional to temperature, is converted into a digital signal by the A/D converter 4. The calculation means 5 that receives this digital value compares the magnitude with a ground fault determination threshold close to 0, and determines that the thermistor 1 is ground fault when it is below the ground fault determination threshold, and otherwise determines that it is normal. Convert to digital value representing temperature. FIG. 4 shows the relationship between the detected voltage (vertical axis) and temperature (horizontal axis) at point P when there is no ground fault, and VA indicates an analog voltage corresponding to the ground fault determination threshold.

[Problem to be solved by the invention] Since the conventional temperature detection device is configured as described above, the detection voltage at point P at high temperature is minute and close to the analog voltage vA equivalent to the dark value for ground fault judgment. Therefore, A/D converter 4
Considering the accuracy of noise and the influence of noise, there was a problem that there was a possibility of incorrectly determining a ground fault at high temperatures, making it difficult to determine a ground fault. This invention was made to solve the above-mentioned problems, and an object thereof is to obtain a temperature detection device that can accurately determine a ground fault regardless of the detected temperature.

[Means to solve the problem]

The temperature detection device of the present invention is a device that determines a ground fault of a thermistor by determining the level of a detection voltage for detecting temperature, and uses the voltage applied to a series connection of a thermistor and a resistor as the detection voltage.

[For production]

In the temperature detection device according to the present invention, the level of the detection voltage changes by the voltage applied to the resistor connected in series with the thermistor, and the difference from the ground fault determination level becomes large, so that the thermistor can be accurately determined to be ground fault.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows the configuration of a temperature detecting device according to an embodiment of the present invention. In the figure, parts that are the same as those in the conventional example are denoted by the same reference numerals 1 to 6 and P as in FIG. 3, and their explanation will be omitted. A resistor 7 is provided between the thermistor 1 and the ground, and is connected in series with the thermistor 1.

Next, the operation of this embodiment will be explained with reference to FIG. The voltage of the DC power supply 6 is divided by the resistance value of the resistor 3, the resistance value of the thermistor 1, and the resistance value of the resistor 7, and the temperature is detected as the voltage at point P. The voltage at point P increases by the voltage applied to resistor 7 in addition to the voltage applied to thermistor 1. The detected voltage at point P is digitized by the A/D converter 4, compared with the ground fault determination dark value by a calculation means, and is converted into temperature data, similar to conventional processing. .

FIG. 2 shows the relationship between the temperature (horizontal axis) and the detected voltage at point P (vertical axis) when there is no ground fault. Compared to the conventional characteristic curve 20, the characteristic curve 10 of this embodiment The voltage applied to the In the case of this invention, even in a high temperature range, the detection voltage at point P when a non-ground fault occurs is an analog voltage corresponding to the ground fault determination dark value ■. Because it is considerably larger, there is no possibility of false ground fault detection.

[Effects of the Invention] As described above, according to the present invention, a resistor is connected in series with the thermistor, the detection voltage is varied by the voltage applied to the resistor, and the level of the detection voltage is determined to determine the ground fault of the thermistor. Since this configuration is configured to perform this, it is possible to accurately determine a thermistor's ground fault without being affected by noise or the accuracy of the A/D converter.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a temperature detection device according to an embodiment of the present invention, Fig. 2 is a diagram comparing the relationship between temperature and detection voltage between a conventional example and an embodiment, and Fig. 3 is a diagram of a conventional temperature detection device. FIG. 4, a configuration diagram of the temperature detection device, is a diagram showing the relationship between temperature and detection voltage according to a conventional example. In the figure, ■...Thermistor, 2...
- Signal processing section, 7...resistance. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a temperature detection device that divides a predetermined voltage using a thermistor, detects the temperature using this divided voltage, and determines a ground fault of the thermistor by determining the level of this detected voltage, a series connection body of the thermistor and a resistor is provided. A temperature detection device characterized in that such a voltage is used as the detection voltage.