Device for remote temperature measurement

 

(57) Abstract:

The inventive device comprises a volumetric microwave resonator in the cavity which is at a distance from the end equal to 1/4 the wavelength of a microwave amplifier with a diode. To the anode of the diode circuit of the amplifier is connected low-pass filter frequency. Filter made in accordance with the formula set out in the description. 3 Il.

The invention relates to techniques for temperature measurement and can be used in mechanical engineering, aviation, aerospace, heat engineering, meteorology and other fields that require remote temperature measurement.

In the heating engineer widespread temperature resistant, gauge, thermoelectric, electronic and other temperature transducers [1].

For example, temperature resistant temperature sensor includes a thermistor in the form of a platinum coil of thin wire placed in a ceramic fixture that is placed in the measured medium.

The principle of thermocouple resistance based on proportional measurement of its electrical resistance on temperature, which is measured by an electronic device to measure the>/P>As a prototype made a device for temperature measurement of rotating objects [2] using surround a microwave resonator including a controlled object, three-dimensional resonator, transmitting antenna, the microwave generator, the receiving antenna, amplifier, comparator frequency, the Registrar.

The sensitive element of the device is a volumetric microwave resonator is made of a material with a large coefficient of thermal expansion, such as aluminum. The resonator is placed on the test object. When measuring the temperature of the object and the resonator changes the linear dimensions of the latter and hence its resonant frequency f:

f = f t (1 - t) where is the coefficient of linear expansion of the material of the resonator.

So, for aluminum = 2,7.10-5then , at frequency f = 10 GHz, the change in f of the resonance frequency on the 1abouttemperature changes of the resonator to be $ 2.7.105Hz. This allows the required accuracy to determine the temperature by measuring the resonance frequency of the microwave resonator.

Remote excitation of oscillations in the microwave resonator by using the transmitting antenna from the microwave generator frequency-modulated Colne at its resonance frequency are perceived receiving antenna, amplified by the amplifier and then fed to the device comparison frequencies, which are also fluctuations of the microwave generator. The output of the comparator is connected to a recording device. This device can be used for temperature measurement of rotating objects such as the rotors of the generators, anchors, traction engines and other

The main disadvantage of the prototype is functional complexity measurement temperature due to the presence of comparator frequency generator of the probing signal and the transmitting antenna. In addition, it provides a relatively small range of measurement (units m).

Increase range of termoizolanti faces to use in difficult conditions of measurement lines, which in turn further complicates and increases the cost of the scheme, as this device is required to convert the value of the temperature in appearance, convenient for transmission in the communication lines.

The purpose of the invention is to simplify the device for remote temperature measurement by eliminating complex devices pair of thermocouple with connection line.

The proposed device for remote ismerem microwave diode, established in the cavity volume of the microwave resonator at a distance from one of its ends, is equal to a quarter wavelength of the volume of the microwave resonator, the filter is connected with the anode of diode microwave amplifier and the input line frequency is connected to the output line, and a filter made in accordance with the formula

t= 1/t. wheret- frequency oscillations emitted by the filter;

tthe delay volume of the microwave resonator.

The combination of distinctive features and properties of the present invention from the literature are not known, therefore it meets the criteria of novelty and inventive step.

In Fig. 1 is a diagram of the device of Fig. 2 - scheme of the oscillator with delayed feedback (AIA), and Fig. 3 shows the results of experimental investigations of the characteristics of the layout generator with AIA.

The proposed device is based on the following provisions.

The length of the waveguide resonator ltwhen measuring temperature from taboutto t and known initial length lowhen t is calculated by the formula

lt- lo(1 +att), where t = t - to- the temperature difference;

t- coefficient of thermal expansion t modified ltthat can be interpreted as the electrical length (delay t) of the resonator.

The delay waveguide resonatortis determined by the formulat= ;;

vg= Co= C, where Vg- the group velocity of the wave in the waveguide;

a - width of the waveguide (wave H1B), hence

t= As shown in Fig. 1, the Converter offers a microwave generator including a long waveguide volumetric microwave resonator 1 with takaratomy 2 at the ends, inside of which the distance from Takoradi 2 installed power microwave reflective type 3 made on latinobarometro diode (spent) or Gunn diode.

Really the choice of the length of the resonator 1 is a compromise between the magnitude of the losses in the resonator 1 and the gain of the amplifier 3 so as to ensure the excess of gain over loss.

To the anode of the diode circuit of the amplifier 3 are connected in series a low-pass filter 4, line 5 connection and a low-frequency frequency 6.

Long microwave resonator 1 and the amplifier 3 is an oscillator with delayed feedback (AIA), the scheme of which is shown in Fig. 2.

Such oscillators have amplitudes of the output frequency, equidistant across the frequency intervalst= (Fig. 3).

As shown by experimental studies of such oscillator in the range of 10 GHz with a long resonator (l = =0,43 m), it generates a periodic sequence of very short radio pulses (0.8 NS) with a repetition period equal tot= 3.6 NS.

The device operates as follows.

Thermocouple (in a cavity: 1, 2, 3) are placed in the medium.

The length of the resonator 1 lounder the influence of temperature changes to a value of ltcorresponding to the ambient temperature. In the resonator 1 is excited by a sequence of short radio pulses, which is detected by the diode 3 in the sequence of radio pulses of lower frequency, from which the filter 4 is allocated harmonic component (in the described experimentt= 278,3 MHz), which is transmitted via the communication line 5, and then use the frequency counter 6 is determined by its frequency.

On the measured value oftand the known values of to, lothat is , a reverse conversion is sequentially calculated t, ltand the ambient temperature t.

Specified polidano in temperature values.

The proposed device for remote measurement of temperature in comparison with the prototype has a more simple scheme for distance measurement by eliminating complex devices pairing signal with the signal of the communication channel.

DEVICE FOR REMOTE TEMPERATURE MEASUREMENT, containing the bulk of the microwave resonator, the line of communication and frequency, characterized in that, to simplify the design, it is equipped with a filter and microwave amplifier with diode installed in the cavity volume of the microwave resonator at a distance from one of its ends, is equal to a quarter wavelength of the volume of the microwave resonator, the filter is connected with the anode of diode microwave amplifier and the input line frequency is connected to the output line, and a filter made in accordance with the formula

t= 1 /t,

wheret- frequency oscillations emitted by the filter;

tthe delay volume of the microwave resonator.

 

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