RU2194956C1 - Procedure measuring spatial distribution of temperature ( versions ) and facility for its realization - Google Patents

Abstract

FIELD: measurement technology, determination of temperature in assemblage of points. SUBSTANCE: procedure measuring spatial distribution of temperature according to first version is carried out by placement of assemblage of temperature-sensitive elements connected in parallel by two-wire line in check points, by supply of alternating voltage signal to one input of line and by recording input alternating current i_in(t). Quartz piezoresonance pickups with different resonance frequencies ω_r1, ω_r2,...ω_ri,...ω_rN, are employed as temperature-sensitive elements. Signal with spectrum overlapping frequency range of quartz piezo-resonance pickups is used in the capacity of alternating voltage signal supplied to one input of two-wire line. In correspondence with second version procedure measuring spatial distribution of temperature is realized by placement of assemblage of temperature-sensitive elements in check points and by use of signal with frequency modulation in range of resonance frequencies of quartz piezoresonance pickups in the capacity of alternating voltage signal supplied to one input of two-wire line. Facility for realization of procedure measuring spatial distribution of temperature includes assemblage of temperature- sensitive elements connected in parallel with the help of two-wire line connected to resistor which is coupled to source of alternating voltage. Quartz piezo-resonance pickups with different resonance frequencies ω_r1, ω_r2,...ω_ri,...ω_rN, are employed as temperature- sensitive elements, recorder incorporates matching circuit, register of amplitude of alternating current, spectrum analyzer, processing and indication unit connected in series. Signal generator with spectrum overlapping frequencies of quartz piezo- resonance pickups is utilized in the capacity of source of alternating voltage. EFFECT: increased accuracy and noise immunity, expanded temperature measurement range of spatial distribution of temperature field. 3 cl, 3 dwg

Description

 The invention relates to measuring technique for determining the temperature at many points.

 Known methods that implement devices for measuring the spatial distribution of temperature (US patent 4875782, CL G 01 K 7/04, 1990; AC 1177684, CL G 01 K 3/02, 1985; 1223053, G 01 K 7/00, 1986 ) based on measuring the electrical resistance of thermosensitive elements located at points of measurement of the temperature field.

 Known devices for measuring the spatial distribution of temperature (US patent 4875782, class G 01 K 7/04, 1990; A.S. 1177684, class G 01 K 3/02, 1985; 1223053, G 01 K 7/00, 1986 )

 The disadvantage of these methods and their devices is the presence of either a mechanical scanning device, or a large number of connecting wires and a switch.

 Closest to the proposed one is a method that implements a device for measuring the spatial distribution of temperature (patent of the Russian Federation 2079822, class G 01 K 7/00, 1997), based on measuring the saturation current of semiconductor thermosensitive elements located at points of interest for measuring the temperature field.

 Closest to the proposed is a device for measuring the spatial distribution of temperature (patent of the Russian Federation 2079822, class G 01 K 7/00, 1997), which contains many heat-sensitive semiconductor elements, a meter and a recorder.

 The disadvantage of this method and device is the low accuracy of the measurements caused by a change in the measured current due to drift of the parameters of the measuring equipment when the temperature changes, aging of the elements, low noise immunity, as well as a low upper limit of the temperature range of measurements, limited by the limiting operating temperature of the pn junction.

 The technical problem to be solved is improving accuracy, noise immunity and expanding the temperature range for measuring the spatial distribution of the temperature field.

The technical problem to be solved in the method of measuring the spatial distribution of temperature (its first version) by placing at a controlled point a plurality of heat-sensitive sensors connected in parallel by a two-wire line, applying an alternating voltage signal to one of the inputs of the line and registering the input alternating current i _in (t) is achieved by in that the temperature-sensitive sensor using quartz piezoresonance sensors with different resonant frequencies _{ω p1, ω p2, ... ω} pi, ... ω pN, as a signal lane alternating voltage supplied to one input of a two-wire line, using a signal with the spectrum overlapping frequency range quartz piezoresonance sensors after registration i _Bx (t) of the input AC its amplitude spectrum calculating S (ω), determine the resonant frequency of quartz piezoresonance sensors ω _{p1 , ω p2, ... ω pi,} ... ω pN position of the maxima of the amplitude spectrum S (ω), and then pre-found experimentally or theoretically known dependence of resonant frequency quartz piezoresonance x sensor temperature ω _pi (t) determined by the desired temperature of the controlled points.

The technical problem to be solved in the method for measuring the spatial distribution of temperature (its second variant) by placing at the controlled points a plurality of temperature-sensitive sensors connected in parallel by a two-wire line, applying an alternating voltage signal to one of the line inputs and registering the input alternating current i _in (t) is achieved by in that the temperature-sensitive sensor using quartz piezoresonance sensors with different resonant frequencies _{ω p1, ω p2, ... ω} pi, ... ω pN, as a signal lane alternating voltage supplied pas one input of a two-wire line, using a signal with frequency in the range of resonance frequencies quartz piezoresonance sensors, check AC input i _Rin (t) at the instants achieve its maximum values measured alternating voltage signal the frequency of which is equal to the value of the resonance the frequencies of the sensors ω _p1 , ω _p2 , ... ω _pi , ... ω _pN , and then according to the previously experimentally found or theoretically known dependence ω _pi (t) of the resonant frequency of quartz piezoelectric resonators Temperature sensors calculate the desired temperature at controlled points.

The technical problem to be solved in a device that implements a method for measuring the spatial distribution of temperature in its first and second variants, containing a variety of heat-sensitive sensors, connected in parallel by a two-wire line connected to a recorder that is connected to an AC voltage source, is achieved by using quartz as heat-sensitive sensors piezoresonance sensors with different resonant frequencies _{ω p1, ω p2, ... ω} pi, ... ω pN, recorder comprises sequentially with unity matching circuit, the registrar AC amplitude, spectrum analyzer, processing and display unit, a signal generator is used as an AC voltage source with the spectrum overlapping frequencies piezoresonance quartz sensors.

 Figure 1 shows a block diagram of a device that implements the method.

 In FIG. Figure 2 shows the temperature-frequency response of a quartz piezoresonance sensor PKTV 206.

 Figure 3 shows a graph of the frequency dependence of the conductivity module of a quartz piezoresonance sensor PKTV 206.

The device (Fig. 1) contains N quartz piezoresonance sensors l _i , a two-wire line 2, a generator 3, a recorder 4, which includes a matching circuit 5, an AC amplitude recorder 6, a spectrum analyzer 7, a processing and indication unit 8. The number of quartz piezoresonance sensors is determined by the required number of temperature control points.

Quartz piezoresonance sensors l _{i are} electrically connected using a two-wire line 2 to the matching circuit 5, the other input of the matching circuit 5 is electrically connected to the generator 3. The output of the matching circuit 5 is electrically connected to the input of the AC amplitude recorder 6, the output of which is connected to the input of the spectrum analyzer 7 The output of the spectrum analyzer 7 is electrically connected to the input of the processing and display unit 8.

Consider the implementation of the method for measuring the spatial distribution of temperature (its first variant) using the device shown in FIG. 1. Generator 3 generates a signal with a spectrum that covers the frequency range of quartz piezoresonance sensors. The signal from the generator 3 through the matching circuit 5 is fed to the input of the two-wire line 2. The matching circuit 5 is necessary to highlight small changes in the input current of the two-wire line 2 caused by the resonance of the quartz piezoresonance sensors l _i against the background of a strong unchanged component of the input signal. The signal from the matching circuit 5 is fed to the AC amplitude recorder 6. Data from the output of the AC recorder 6 is fed to a spectrum analyzer 7, which makes it possible to calculate the amplitude spectrum of the input current S (ω) from the time sample of the input current i _in (t) of the two-wire line 2. The data on the amplitude spectrum are sent to the processing and display unit 8, in which, using the previously experimentally found or theoretically known dependence of the resonance frequency ω _pi (t) of the quartz piezoresonance sensors l _i , the desired temperature is calculated at the controlled points and its indication is made.

Consider the implementation of the method of measuring the spatial distribution of temperature (its second option) using the device shown in figure 1. Generator 3 generates a frequency modulated signal in the resonant frequency range of quartz piezoresonance sensors. The signal from the generator 3 through the matching circuit 5 is fed to the input of the two-wire line 2. The matching circuit 5 is necessary to isolate small changes in the input current of the two-wire line 2 caused by the resonance of the quartz piezoresonance sensors l _i against the background of a strong unchanged component of the input signal. The signal from the matching circuit 5 is fed to the AC amplitude recorder 6. Data from the output of the AC recorder 6 is fed to a spectrum analyzer 7, which allows determining the frequency of the input alternating current. The spectrum analyzer determines the frequencies of the alternating current i _in (t) when it reaches its maximum values, these frequencies are equal to the resonant frequencies of the sensors ω _p1 , ω _p2 , ... ω _pi , ... ω _pn . Data on the resonant frequencies of the quartz piezoresonance sensors l _i are supplied to the processing and display unit 8, in which, using the previously experimentally found or theoretically known dependence of the resonant frequency ω _pi (t) of the resonant frequency of the quartz piezoresonance sensors l _i on the temperature, the desired temperature is calculated at the controlled points and its indication.

 We show that the proposed method allows to achieve the solution of the technical problem - to increase the accuracy and noise immunity of measuring the spatial temperature distribution.

 Existing traditional methods and sensors for measuring temperature (US patent 4875782, CL G 01 K 7/04, 1990; A.S. 1177684, CL G 01 K 3/02, 1985; 1223053, CL G 01 K 7/00 , 1986) allow us to measure, mainly, only local, point, characteristics of thermophysical fields. To measure the temperature of distributed objects, it is necessary to use many point (discrete) sensors located on the measurement object. Using a traditional ideology, the construction of multi-point temperature sensors leads to a significant complication of the measuring equipment and an increase in its volume, as well as to significant material costs, since in this case the system is multi-channel with the number of measuring channels equal to the number of sensors. To build such a multi-channel system, a large number (tens and hundreds) of connecting conductors of sensors with a measuring system is required.

 A device for measuring the spatial distribution of temperature described in the patent of the Russian Federation 2079822, class. G 01 K 7/00, 1997, built on a different principle. In it, many temperature-sensitive sensors are connected in parallel using a two-wire line. At the same time, it becomes possible to achieve a several-fold reduction in the volume of secondary equipment (a decrease in proportion to the number of measuring channels), and a reduction in the total length of connecting lines and cables by the same amount.

 However, the accuracy and noise immunity of this device remains low. It uses semiconductor temperature sensors. The temperature is calculated based on measurements of the amplitude of the sensor current. Since the current amplitude is an informative parameter, the noise of the equipment, electromagnetic interference, the drift of the parameters of the measuring equipment when the temperature changes, aging of the elements, etc. will lead to a random change in this amplitude, and therefore, to a decrease in the accuracy of temperature measurement.

The upper limit of the temperature range of measurements of semiconductor sensors is limited by the limiting operating temperature of the pn junction and for some diodes is up to 140 ^o C [1, diode KD213L].

The use of temperature-sensitive quartz piezoresonance sensors with spaced frequencies as point sensors provides several advantages over other types of sensors. Such sensors have:
- increased accuracy of temperature measurement in the operating range from -50 to + 370 ^o C [2];
- increased noise immunity due to the conversion of temperature into a frequency output signal.

 Using these sensors, it is possible to measure the temperature field of a distributed object at many points with an accuracy of 0.1% [2], and only one channel is required for transmitting measurement information to the secondary equipment.

 One of the types of quartz piezoresonance sensors manufactured by the industry is the tuning fork quartz piezoresonance temperature sensors RKTV 206. The main characteristics of the quartz piezoresonance sensor RKTV 206 are shown in the table.

The quartz piezoresonance sensor RKTV 206 has a temperature characteristic described by the following expression [2]:
f (t) = f ₀ | A ₁ (tt ₀ ) | A ₂ (tt ₀ ) ² , (1)
where f (t) is the frequency of the quartz piezoresonance sensor (Hz) at the current temperature t ( ^o C);
f ₀ is the frequency of the quartz piezoresonance sensor (Hz) at a reference temperature value ( ^o С);
t ₀ - reference value of temperature.

The coefficients for the quartz piezoresonance sensor RKTV 206 are [2]:
A _l = -1.76 ± 0.1 Hz / ^o С, A ₂ = -0.0031 ± 0.0001 Hz / ^o С in the operating temperature range -50 ... +370 ^o С.

 A graph of the temperature frequency response of a quartz piezoresonance sensor with a central frequency of 34 kHz, calculated in accordance with (1), is shown in FIG. 2. By measuring the resonator frequency, the temperature of the sensor is calculated from the temperature-frequency characteristic.

 Thus, by placing quartz piezoresonance sensors at temperature measuring points and connecting them in parallel using a two-wire line, to calculate the temperature, it is necessary to measure their resonant frequencies. In order to do this, a signal with a spectrum overlapping the frequencies of the quartz piezoresonance sensors is supplied to the input of the two-wire line (Fig. 1) from the generator 3. In response to such an effect, free oscillations arise at quartz piezoresonance sensors at the frequencies of their successive resonances. By registering these oscillations with an AC recorder 6 and calculating their spectrum with a spectrum analyzer 7, the resonant frequencies of all the sensors are determined. Further, using the processing and display unit 8, temperatures are calculated from the found frequencies of the sensors and from the known temperature-frequency characteristics of the sensors, the form of which is shown in FIG. 2.

 If a signal with a relatively slow (in comparison with the decay time of the natural oscillations of the sensors) linear frequency change is applied to the input of the two-wire line 2, then the frequency dependence of the input conductivity or input resistance of the line with sensors can be measured. The frequency dependence of the conductivity module of a quartz piezoresonance sensor is shown in FIG. 3 [3]. The conductivity of the quartz piezoresonance sensor in the resonance region has a narrow peak. By measuring the frequency at which the maximum conductivity of the sensor is located, it is possible to determine its resonant frequency. If several sensors are connected in parallel to the line, the graph of the frequency dependence of the line conductivity will have several peaks, each of which corresponds to the resonance of a specific sensor. Further, using the processing and display unit 8, temperatures are calculated from the found frequencies of the sensors and from the known temperature-frequency characteristics of the sensors.

 A prototype device for measuring the spatial distribution of temperature was made on the basis of quartz piezoresonance sensors RKTV 206. The generator was assembled on the basis of operational amplifiers K140UD7. The matching circuit is based on a differential amplifier based on K544UD1 microcircuits. The AC amplitude recorder was an ADC unit based on a computer I / O signal board in the computer - L305 of the company .... The spectrum analyzer and the processing and indication unit were performed on a computer and LabView software package.

 Thus, when using quartz piezoresonance sensors, it is possible to increase the accuracy of measuring the spatial distribution of temperature, since these sensors have a higher accuracy class than semiconductor sensors. Quartz piezoresonance sensors can increase the noise immunity of measurements, since the information parameter is the signal frequency, and not the amplitude. Also extends the upper limit of the temperature range of measurements.

 We have shown that, using piezoresonance sensors connected in parallel using a two-wire line, it is possible to measure the spatial distribution of temperature, while increasing accuracy, noise immunity of measurements, and expanding the upper limit of the temperature range of measurements.

List of references
1. Semiconductor devices: Diodes, thyristors, optoelectronic devices. Reference book / A.V..Bayukov, A.B.Gitsevich, A.A. Zaitsev and others; Under the total. ed. N.N. Goryunova. - M.: Energoatomizdat, 1983, - 744 p.

 2. Technical passport of the resonator of quartz thermosensitive high-temperature RKTV 206 TU 25-1862.0013-88 Special Design and Technological Bureau of Electronics, Instrument Engineering and Automation, Uglich.

 3. Malov VV Piezoresonance sensors. - 2nd ed., Revised. and add. - M .: Energoatomizdat, 1989.

Claims (3)

1. The method of measuring the spatial temperature distribution by placing at a controlled point a plurality of temperature-sensitive sensors connected in parallel by a two-wire line, applying an alternating voltage signal to one of the line inputs and registering the input alternating current i _in (t), characterized in that they are used as temperature-sensitive sensors quartz piezoresonance sensors with different resonant frequencies ω _p1 , ω _p2 , ... ω _pi , ... ω _pN , as an AC voltage signal applied to one of the inputs two-wire line, use a signal with a spectrum that covers the frequency range of quartz piezoresonance sensors, after registering the input alternating current i _in (t), its amplitude spectrum S (ω) is calculated, the resonance frequencies of quartz piezoresonance sensors ω _p1 , ω _p2 , ... ω _pi, ... ω _pN position of the maxima of the amplitude spectrum S (ω), and then pre-found experimentally or theoretically known dependence of resonant frequency of the quartz sensor piezoresonance temperature ω _pi (t) defines the desired th temperature controlled locations. 2. A method of measuring the spatial distribution of temperature by placing at a controlled point a plurality of heat-sensitive sensors connected in parallel by a two-wire supply line to one of the inputs of the AC voltage signal line and registering the input AC current i _in (t), characterized in that quartz is used as heat-sensitive sensors piezoresonance sensors with different resonant frequencies ω _p1 , ω _p2 , ... ω _pi , ... ω _pN , as an AC voltage signal applied to one of the inputs two-wire line, use a signal with a frequency modulation in the resonant frequency range of quartz piezoresonance sensors, when registering the input alternating current i _in (t) at the times of reaching its maximum values, measure the frequencies of the alternating voltage signal, which are equal to the values of the resonant frequencies of the sensors ω _p1 , ω _p2 , ... ω _pi, ... ω _pN, and then pre-found experimentally or theoretically known relationship ω _pi (t) of the resonant frequency of the quartz sensor piezoresonance desired temperature is calculated The temperature in the controlled points. 3. A device for measuring the spatial distribution of temperature, containing many heat-sensitive sensors, connected in parallel by a two-wire line connected to a recorder, which is connected to an AC voltage source, characterized in that quartz piezoresonance sensors with different resonant frequencies ω _p1 , ω _{p2 are} used as heat-sensitive sensors , ... ω _pi , ... ω _pN , the recorder contains a series-connected matching circuit, an AC amplitude recorder, analysis a spectrum torus, a processing and indication unit, a signal generator with a spectrum that overlaps the frequencies of quartz piezoresonance sensors was used as an AC voltage source.

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