CN202442811U - Structure of electronic temperature measurement circuit - Google Patents

Abstract

The utility model relates to a structure of an electronic temperature measurement circuit. The circuit structure comprises a thermistor, a reference resistor, an oscillation circuit module, a temperature measurement-counter module, a memory module, a measurement information output module, a self-regulation module, and a test change-over switch. The thermistor and the reference resistor are connected with the measurement information output module via the oscillation circuit module, the temperature measurement-counter module, and the memory module. The oscillation circuit module is separately connected with the self-regulation module and the temperature measurement-counter module by the test change-over switch. Output signals from the self-regulation module are transmitted to the memory module. According to the structure of the electronic temperature measurement circuit, an internal predetermined temperature curve of the thermistor is self-regulated based on the central resistance value of the thermistor, and a correction coefficient is stored, so that temperature curves of thermistors with different central resistance values can be well fitted. Besides, the cost is reduced with a reduction in measurement errors, and the structure is simple and practical, providing a stable and reliable working performance and a broaden application scope.

Description

The electron temperature measurement circuit structure

Technical field

The utility model relates to the temperature survey field, and particularly the electron temperature measurement technical field specifically is meant a kind of electron temperature measurement circuit structure.

Background technology

In the prior art, electronic thermometer generally is to be that temperature and the resistance relation of the thermistor of a specific electrical resistance (for example specified temp is 37 ℃, and the center resistance is 30K) deposits in the internal storage with the center resistance.But the center resistance of thermistor allows the error of 1% (29.7K is to 30.3K) usually; And because the nonlinear characteristic of thermistor itself; The thermistor of concentricity resistance not; Its temperature curve is inequality, and the preset temperature curve of chip internal is unique, thereby causes the error measured.

See also shown in Figure 1ly, it is the module diagram of traditional electric body-temperature metering circuit, and RS is a thermistor, and RF is a reference resistance.According to the RC vibration theory, the thermometric counting module is counted respectively the waveform of reference resistance and thermistor.Suppose in identical Measuring Time, reference resistance RF to be count down to a certain fixed value N ₃₇, RS count down to N1 to thermistor, then satisfies formula N ₃₇* T _RF=N1 * T _RSAccording to count results

Because this algorithm is oscillation-damped device constant k basically _OscInfluence, so be proportional to resistance value oscillation period,

According to the value of N1, in the ROM look-up table, search corresponding temperature, export through output module.Because 37 ℃ of the normally specified temps of storing in the ROM look-up table, the center resistance is the temperature curve of the thermistor of 30K, and external reference resistance 30K normally.Therefore 37 ℃ the time, N1=N ₃₇But because the center resistance error of thermistor is generally 1% (29.7K is to 30.3K), its temperature curve of the thermistor of concentricity resistance is not inequality, thereby has caused the error of measuring.

Therefore when production test, roughly there are two kinds of improvement ways:

The one, in when test, fully according to the curve of the thermistor of reality, rewritting circuit temperature inside curve;

The 2nd, in circuit, build resistance and capacitance compensation network and switch control logic or in build parameter list, utilize outside corrective system to choose suitable compensation combination, utilize to increase voltage, modes such as current fusing keep selected parameter group.

Rewriteeing temperature curve fully needs the debug time of labor aborning, utilizes outside corrective system to carry out the support that parametric compensation then needs outside software and hardware, has increased production cost.

The utility model content

The purpose of the utility model is to have overcome above-mentioned shortcoming of the prior art, provide a kind of can be according to the preset thermistor curve of the center resistance self-regulation of thermistor, better realize match not the thermistor of concentricity resistance temperature curve, significantly reduce testing cost, obviously reduce measuring error, simple and practical, stable and reliable working performance, scope of application electron temperature measurement circuit structure comparatively widely.

In order to realize above-mentioned purpose, the electron temperature measurement circuit structure of the utility model has following formation:

This electron temperature measurement circuit structure; Comprise thermistor, reference resistance, oscillatory circuit module, thermometric counting module, memory module and metrical information output module; Described thermistor all is connected through described oscillatory circuit module, thermometric counting module, memory module and described metrical information output module with reference resistance; Its principal feature is; Also comprise self-regulation module and test change-over switch in the described circuit structure; Described oscillatory circuit module is connected with the thermometric counting module with described self-regulation module respectively through described test change-over switch, and the output signal of described self-regulation module delivers to described memory module, and this self-regulation module is according to the center resistance of described thermistor and the oscillation frequency of reference resistance; Temperature curve to preset in the described memory module is revised, and correction factor is preserved.

Self-regulation module in this electron temperature measurement circuit structure comprises:

Counting unit is connected with described test change-over switch, is used in the identical time, the central value of described thermistor and the waveform of reference resistance being counted;

Comparer is connected with described counting unit, is used for the comparison count results, obtains correction factor α;

The correction factor storage unit is connected with described comparer, is used to store correction factor α.

Oscillatory circuit module in this electron temperature measurement circuit structure is the RC oscillator.

Memory module in this electron temperature measurement circuit structure is the ROM storer.

Adopted the electron temperature measurement circuit structure of this utility model, because it need not rely on outside software and hardware, can be according to the center resistance of thermistor; The thermistor temp curve of self-regulation internal preset, and can correction factor preserved, thereby the better match temperature curve of the thermistor of concentricity resistance not; When reducing testing cost, reduced measuring error, and also simple and practical; Stable and reliable working performance, the scope of application are comparatively extensive.

Description of drawings

Fig. 1 is a temperature measuring circuit high-level schematic functional block diagram of the prior art.

Fig. 2 is the electron temperature measurement circuit structure high-level schematic functional block diagram of the utility model.

Fig. 3 is the built-in function cell schematics of the self-regulation module in the electron temperature measurement circuit structure of the utility model.

Embodiment

In order more to be expressly understood the technology contents of the utility model, the special following examples of lifting specify.

See also Fig. 2 and shown in Figure 3; This electron temperature measurement circuit structure; Comprise thermistor, reference resistance, oscillatory circuit module, thermometric counting module, memory module and metrical information output module; Described thermistor all is connected through described oscillatory circuit module, thermometric counting module, memory module and described metrical information output module with reference resistance; Wherein, also comprise self-regulation module and test change-over switch in the described circuit structure, described oscillatory circuit module is connected with the thermometric counting module with described self-regulation module respectively through described test change-over switch; And the output signal of described self-regulation module is delivered to described memory module; This self-regulation module is according to the center resistance of described thermistor and the oscillation frequency of reference resistance, and temperature curve preset in the described memory module is revised, and correction factor is preserved.

Wherein, described self-regulation module comprises:

(1) counting unit is connected with described test change-over switch, is used in the identical time, the central value of described thermistor and the waveform of reference resistance being counted;

(2) comparer is connected with described counting unit, is used for the comparison count results, obtains correction factor α;

(3) correction factor storage unit is connected with described comparer, is used to store correction factor α.

Simultaneously, the center resistance error of described thermistor is ± 1% o'clock, and the scope of described correction factor α is 0.99～1.01; The duty of described test switching switch control circuit, when this test change-over switch was set to test pattern, the central value of described thermistor and the oscillation frequency of reference resistance were delivered to described self-regulation module, produced correction factor α; When this test change-over switch is set to normally use pattern; The oscillation frequency of described thermistor and reference resistance is delivered to described thermometric counting module; According to count results, and combine described correction factor α, in described memory module, find out correct corresponding temperature.

In the middle of reality is used; Thermistor in the utility model, reference resistance, oscillatory circuit module, thermometric counting module, memory module and metrical information output module, self-regulation module and test change-over switch; And the counting unit in the self-regulation module, comparer, the correction factor storage unit all can be corresponding to the particular hardware circuit in the circuit structure; Therefore these module/unit only utilize hardware circuit just can realize, need not assist with specific Control Software and promptly can realize corresponding function automatically.

Simultaneously, the related self-regulation of thermometer measure circuit of the utility model is the production field that is used for factory, is in order to solve the bad problem of thermistor consistance.And in test process, the preset temperature curve of chip internal is revised, promptly preserve, can not revise again.

The thermistor that wherein relates to, reference resistance are through the RC oscillatory circuit, directly become clock signal; Be used for rolling counters forward; Simultaneously, the utility model is through the comparison to the rolling counters forward result, obtains concrete corrected parameter; Standard temperature curve to prestoring among the ROM is made amendment, and preserves.

The following formulate of usefulness that the resistance-temperature characteristics of general thermistor can be similar to:

$R=R_0\×e^{\{B\×[\frac{1}{T}-\frac{1}{T_0}\left]\right\}};$

Wherein: T (K)=t (℃)+273.15

Resistance when R0---temperature is T0

Resistance when R---temperature is T

In fact, thermistor constant B is not what fix, therefore in bigger temperature range, uses formula calculated resistance value, can have bigger error.Generally choose 32 ℃～44 ℃ as between measurement zone such as the body temperature meter, the performance of this interval thermistor is near linear.

The oscillation frequency of RC oscillator is: $f=\frac{1}{k_{\mathrm{Osc}}\×R\×C};$

Wherein the oscillator constant is: $k_{\mathrm{Osc}}=\mathrm{Ln}[\left(\frac{V_H}{V_L}\right)\×\frac{(V_{\mathrm{DD}}-V_L)}{(V_{\mathrm{DD}}-V_H)}];$

In the following formula, V _H, V _LBe Schmidt trigger transition high level and low level, V _DDBe supply voltage.

Seeing also shown in Figure 2 is that the utility model is described can self-regulating electric body-temperature metering circuit.This circuit has comprised a self-regulation module and test change-over switch TEST.Work as TEST=1, circuit gets into test pattern, and the central value of thermistor and the oscillation frequency of reference resistance get into the self-regulation module, through handling, obtains correction factor, and preserves.Work as TEST=0, circuit gets into normal use pattern, and the oscillation frequency of thermistor and reference resistance then gets into the thermometric counting module, according to count results, and combines correction factor, in ROM, finds out correct corresponding temperature.

Fig. 3 is a specific embodiment of the self-regulation module that comprises of the described electric body-temperature metering circuit of the utility model, can comprise counting module, comparer and correction factor storage unit.When the oscillation frequency of the central value of thermistor and reference resistance gets into the self-regulation module, counter is counted oscillator signal in the identical time respectively, at one time in, the count value of the oscillator signal of thermistor central value is N2.In comparing unit with N2 and standard N ₃₇Compare, control module is stored in correction factor α in the correction factor storage unit according to comparative result, and the temperature curve in the circuit is revised.

When the described electric body-temperature metering circuit of the utility model operate as normal, the number of oscillation of supposing the thermistor waveform is N1, so then is modified to N1+N by this corrected parameter ₃₇(1-a).When the central value of thermistor was higher than reference resistance, according to the RC vibration, the oscillation frequency of thermistor was lower than the oscillation frequency of reference resistance, N2＜N ₃₇, correction factor a＜1.When the central value of thermistor was lower than reference resistance, according to the RC vibration, the oscillation frequency of thermistor was higher than the oscillation frequency of reference resistance, N2＞N ₃₇, correction factor a＞1.When the central value of thermistor equals reference resistance, N2=N ₃₇, correction factor a=1.When the center resistance error of thermistor was generally 1% (29.7K is to 30.3K), the scope of correction factor a was 0.99～1.01.

The utility model can self-regulating thermometer measure circuit, wherein comprised a self-regulation module and test change-over switch TEST.

This can self-regulating thermometer measure circuit in, the duty of said test change-over switch TEST may command circuit.As test change-over switch TEST=1, circuit gets into test pattern, and the central value of thermistor and the oscillation frequency of reference resistance get into the self-regulation module, produce correction factor α.As test TEST=0, circuit gets into normal use pattern, and the oscillation frequency of thermistor and reference resistance then gets into the thermometric counting module, according to count results, and combines correction factor α, in ROM, finds out correct corresponding temperature.

This can self-regulating thermometer measure circuit in the self-regulation module comprise:

Counting module is used in the identical time, the central value of thermistor and the waveform of reference resistance being counted;

Comparer is used for count results is compared, and obtains correction factor α;

The correction factor storage unit is used to store correction factor α.

Adopted above-mentioned electron temperature measurement circuit structure, because it need not rely on outside software and hardware, can be according to the center resistance of thermistor; The thermistor temp curve of self-regulation internal preset, and can correction factor preserved, thereby the better match temperature curve of the thermistor of concentricity resistance not; When reducing testing cost, reduced measuring error, and also simple and practical; Stable and reliable working performance, the scope of application are comparatively extensive.

In this instructions, the utility model is described with reference to its certain embodiments.But, still can make various modifications and conversion obviously and not deviate from the spirit and the scope of the utility model.Therefore, instructions and accompanying drawing are regarded in an illustrative, rather than a restrictive.

Claims (4)

1. electron temperature measurement circuit structure; Comprise thermistor, reference resistance, oscillatory circuit module, thermometric counting module, memory module and metrical information output module; Described thermistor all is connected through described oscillatory circuit module, thermometric counting module, memory module and described metrical information output module with reference resistance; It is characterized in that; Also comprise self-regulation module and test change-over switch in the described circuit structure; Described oscillatory circuit module is connected with the thermometric counting module with described self-regulation module respectively through described test change-over switch, and the output signal of described self-regulation module delivers to described memory module, and this self-regulation module is according to the center resistance of described thermistor and the oscillation frequency of reference resistance; Temperature curve to preset in the described memory module is revised, and correction factor is preserved.

2. electron temperature measurement circuit structure according to claim 1 is characterized in that, described self-regulation module comprises:

Counting unit is connected with described test change-over switch, is used in the identical time, the center resistance of described thermistor and the waveform of reference resistance being counted;

Comparer is connected with described counting unit, is used for the comparison count results, obtains correction factor α;

The correction factor storage unit is connected with described comparer, is used to store correction factor α.

3. electron temperature measurement circuit structure according to claim 1 and 2 is characterized in that, described oscillatory circuit module is the RC oscillator.

4. electron temperature measurement circuit structure according to claim 1 and 2 is characterized in that, described memory module is the ROM storer.

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