CN211576401U - Low-impedance temperature sensor - Google Patents
Low-impedance temperature sensor Download PDFInfo
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- CN211576401U CN211576401U CN201921016467.XU CN201921016467U CN211576401U CN 211576401 U CN211576401 U CN 211576401U CN 201921016467 U CN201921016467 U CN 201921016467U CN 211576401 U CN211576401 U CN 211576401U
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Abstract
The utility model discloses a low impedance temperature sensor, which comprises a sampling circuit and a power supply module, wherein the sampling circuit comprises an ADC chip, a thermistor and a reference resistor; wherein the thermistor is connected in series with the reference resistor; the chip is characterized in that INP pins and INN pins of the chip are respectively connected to two ends of a reference resistor and used for measuring voltages at two ends of the reference resistor; the REF (+), REF (-) pins of the chip are respectively connected with two ends of the thermistor and used for measuring the voltage at the two ends of the thermistor as the reference voltage of the chip sampling; the utility model discloses can make two input resistance's output impedance less, and the input impedance requirement of ADC chip also reduces thereupon.
Description
Technical Field
The utility model relates to a measure the field, more specifically, related to a low impedance temperature sensor.
Background
A low-impedance temperature sensor refers to a sensor that can sense temperature and convert the sensed temperature into a usable output signal, and it is a common practice to use a thermistor, whose resistance value changes with temperature, as a measuring element. In order to collect resistance data of the thermistor and convert the resistance data into a relevant temperature value, an ADC chip with an analog-to-digital conversion function is generally used for data sampling. Sampling is an important step in the analog-to-digital conversion process, and in the sampling process, a chip needs to use a reference voltage as an amplitude reference of a detected signal, and the reference voltage is generally required to be larger than the voltage value of the detected signal. The current conventional techniques for sampling thermistors for ADC chips in the field are the following two approaches:
the ADC chip takes voltage values at two ends of a resistor Rref with a fixed resistance value as a sampled reference voltage Uref, and samples a tested thermistor Rx through a formula:
calculating the resistance value of Rx, but because the reference voltage Uref is required to be larger than the voltage Ux at two ends of the measured thermistor Rx in ADC chip sampling, on the basis that Rx and Rref are connected in series, the sampling requirement Rref is larger than Rx; the disadvantage of this method is that the output impedance of Rx and Rref is large and the variation with temperature is also large, which has high requirement on the input impedance of ADC chip;
2, the ADC chip takes the internal reference voltage as the reference voltage of the sampling, respectively samples the detected thermistor Rx and the reference resistor Rref, and then passes through two formulas ①
②
The resistance value of Rx can be obtained by simultaneous ①② calculation (AD1 and AD2 are digital signals after ADC chip is carried out with analog-digital conversion), although the problem of larger impedance in the first mode is overcome, the new problem is introduced because the input end needs to be switched to carry out two times of measurement in the second mode, and under the same range and precision, the output speed of ADC after analog-digital conversion is at least twice slower than that in the first mode.
SUMMERY OF THE UTILITY MODEL
Based on this technical background, the technical problems to be solved are as follows: how to reduce the requirement on the input impedance of the ADC chip without affecting the output speed of the ADC chip.
In order to solve the technical problem, the utility model provides a low temperature sensor who hinders, the utility model discloses a following technical scheme:
a low-impedance temperature sensor comprises a sampling circuit and a power supply module, wherein the sampling circuit comprises a chip, a thermistor, a reference resistor and the power supply module; wherein the thermistor is connected in series with the reference resistor; the chip comprises a reference resistor, a power supply module, a sampling circuit, a reference resistor, a thermistor and a power supply module, wherein INP pins and INN pins of the chip are respectively connected with two ends of the reference resistor and used for measuring voltages at two ends of the reference resistor, REF (+), REF (-) pins of the chip are respectively connected with two ends of the thermistor and used for measuring the voltages at two ends of the thermistor as reference voltages for chip sampling, and the power supply module is connected with the sampling circuit in series.
Further, the thermistor includes a semiconductor thermistor, a metal thermistor, and an alloy thermistor.
Further, the thermistors include positive temperature coefficient thermistors and negative temperature coefficient thermistors.
Further, the chip is an ADC chip having an analog-to-digital conversion function.
In the prior art, the ADC chip uses an internal reference voltage (for example, the internal reference voltage of ADC0809 is 4.75-5.25V) or a voltage measured across a reference resistor as a reference voltage for sampling, and the two methods have been written into a mainstream ADC product manual or data manual in the market as standard methods of use. And compare with prior art, the utility model discloses it all is the routine of being followed the input and measured the signal to have overturned traditional ADC application, will survey thermistor RX both ends voltage Ux as the reference voltage of ADC chip sampling to measure its voltage value with the Rref of fixed resistance value as the input, reachd the temperature value that thermistor Rx corresponds according to thermistor's characteristic again. This avoids the problems associated with the two currently conventional techniques mentioned in the background.
To sum up, compare with prior art, the utility model discloses there is following beneficial effect: according to the technical scheme, the input resistor (the sum of the resistance values of Rref and Rx) is smaller than that of the prior art under the condition of realizing the same range, the output impedance between the two resistors is smaller, and the requirement on the input impedance of the ADC chip is reduced.
Drawings
In order to illustrate the present application or prior art more clearly, a brief description of the drawings needed for the description of the embodiments or prior art will be given below, it being clear that the drawings in the following description are some embodiments of the present application and that other drawings can be derived from them by a person skilled in the art without inventive effort.
FIG. 1 is a first prior art circuit diagram;
FIG. 2 is a circuit diagram of a prior art circuit;
fig. 3 is a circuit diagram of an embodiment of the low impedance temperature sensor of the present invention;
fig. 4 is a second circuit diagram of the embodiment of the low impedance temperature sensor of the present invention.
Detailed Description
In order to make the technical solution of the present invention better understood, the following description is given in conjunction with the prior art and the problems thereof, so as to more clearly and completely describe the technical solution in the embodiments of the present invention. It is obvious that the embodiments described below are only some of the embodiments of the present invention, and not all of them. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts shall belong to the protection scope of the present invention.
Based on the background, the conventional techniques for sampling the thermistor by the ADC chip in the prior art are as follows:
1. as shown in fig. 1, the ADC chip takes the voltage values at two ends of the resistor Rref with a fixed resistance value as the reference voltage Uref for sampling, and samples the thermistor Rx to be measured, and then passes through the formula:
the resistance of Rx is calculated but since the reference voltage Uref is required to be greater than the thermistor R to be measured in ADC chip samplingThe voltage Ux at the two ends of x requires Rref to be larger than Rx on the basis that Rx and Rref are connected in series, and the defects are as follows: the output impedance of Rx and Rref will be large and will increase with temperature, and there is a high demand for the input impedance of the ADC chip.
2. Referring to fig. 2, the ADC chip takes the internal reference voltage as the reference voltage of the sample, and samples the measured thermistor Rx and the reference resistor Rref respectively and then passes through two formulas ①
②
(AD1 and AD2 are digital signals after analog-digital conversion of the ADC chip), the resistance value of Rx can be calculated by simultaneous ①②. the circuit overcomes the defect of the first mode, but the new problem is caused because the input end needs to be switched to carry out two times of measurement, namely, the output speed of the ADC after the analog-digital conversion is at least one time slower than that of the first mode under the same measuring range and precision.
In order to overcome the problems of the prior art and to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.
Example 1: a low-impedance temperature sensor comprises a sampling circuit, as shown in FIG. 3, wherein the sampling circuit comprises a chip, a thermistor, a reference resistor and a power supply module; one end of the reference resistor is connected with the power supply module, and the other end of the reference resistor is connected with one end of the thermistor; the other end of the thermistor is grounded, and the thermistor is connected with the reference resistor in series; the chip is characterized in that INP pins and INN pins of the chip are respectively connected to two ends of a reference resistor and used for measuring voltages at two ends of the reference resistor; the REF (+), REF (-) pins of the chip are respectively connected with two ends of the thermistor and used for measuring the voltage at the two ends of the thermistor as the reference voltage of the chip sampling; wherein the chip is a 16-bit ADC chip with analog-to-digital conversion functionality. The thermistor is a negative temperature coefficient thermistor, taking the thermistor 503ET as an example, the reference resistor Rref is 10K, 16 bitsADC corresponds to K65536 according to the formula:
the reciprocal of the resistance of the thermistor Rx is calculated to obtain the temperature corresponding AD value as shown in the following table, and the temperature value measured at this time can be obtained by reading the AD value.
| Temperature (. degree.C.) | 1/Rx(Ω) | AD |
| 0 | 1/161.9 | 4048 |
| 10 | 1/99.13 | 6611 |
| 20 | 1/62.38 | 10506 |
| 30 | 1/40.24 | 16286 |
| 40 | 1/26.58 | 24656 |
| 50 | 1/17.93 | 36551 |
TABLE-503 ET temperature comparison table
Example 2: a low-impedance temperature sensor comprises a sampling circuit, as shown in FIG. 4, wherein the sampling circuit comprises a chip, a thermistor, a reference resistor and a power supply module; one end of the thermistor is connected with the power supply module, and the other end of the thermistor is connected with one end of the reference resistor; the other end of the reference resistor is grounded, and the thermistor and the reference resistor are connected in series; the chip is characterized in that INP pins and INN pins of the chip are respectively connected to two ends of a reference resistor and used for measuring voltages at two ends of the reference resistor; the REF (+), REF (-) pins of the chip are respectively connected with two ends of the thermistor and used for measuring the voltage at the two ends of the thermistor as the reference voltage of the chip sampling; wherein the chip is a 16-bit ADC chip with analog-to-digital conversion functionality. The thermistor is a positive temperature coefficient thermistor, taking a platinum resistor PT1000 as an example, taking reference resistor Rref as 510K, and 16-bit ADC corresponding to K as 65536, according to the formula:
the resistance of the thermistor Rx is calculated, and the temperature-corresponding AD value obtained is shown in the following table two, and the temperature value measured at the moment can be obtained through the read AD value.
| Temperature (. degree.C.) | Resistance (omega) | AD value |
| 0 | 1000 | 33423 |
| 10 | 1039.25 | 32161 |
| 20 | 1077.935 | 31007 |
| 30 | 1116.729 | 29930 |
| 40 | 1155.408 | 28928 |
| 50 | 1193.971 | 27993 |
TABLE II platinum resistance PT1000 thermistor temperature comparison table.
Claims (4)
1.A low-impedance temperature sensor comprises a sampling circuit and a power supply module, and is characterized in that the sampling circuit comprises a chip, a thermistor and a reference resistor, wherein the thermistor and the reference resistor are connected in series; the INP and INN pins of the chip are respectively connected with two ends of the reference resistor and used for measuring the voltage at the two ends of the reference resistor; and REF + and REF-pins of the chip are respectively connected with two ends of the thermistor and used for measuring the voltage at the two ends of the thermistor as the reference voltage for chip sampling, and the power supply module is connected with the sampling circuit in series.
2.A low impedance temperature sensor as claimed in claim 1, wherein said thermistor is a semiconductor thermistor or a metal thermistor or an alloy thermistor.
3. A low impedance temperature sensor as claimed in claim 1, wherein said thermistor is a positive temperature coefficient thermistor or a negative temperature coefficient thermistor.
4. A low impedance temperature sensor as claimed in claim 1 wherein said chip is an ADC chip with analog to digital conversion functionality.
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| CN201921016467.XU CN211576401U (en) | 2019-07-02 | 2019-07-02 | Low-impedance temperature sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110388993A (en) * | 2019-07-02 | 2019-10-29 | 杨晨 | A kind of Low ESR temperature sensor and its thermometry |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110388993A (en) * | 2019-07-02 | 2019-10-29 | 杨晨 | A kind of Low ESR temperature sensor and its thermometry |
| CN110388993B (en) * | 2019-07-02 | 2024-06-18 | 杨晨 | Low-impedance temperature sensor and temperature measurement method thereof |
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