SU1747947A1 - Piezoelectric-crystal converter of temperature - Google Patents

Abstract

The invention relates to thermometry and allows to improve the accuracy of measurements by increasing the conversion steepness. A piezoelectric temperature converter (FPT) with a frequency output contains an amplifier 1, made on a transistor 2, connected according to a common collector circuit, a multimode temperature-sensitive quartz resonator 7, a series LC- circuit connected between the emitter and collector of the transistor. The midpoint of the LC circuit is connected via a second phase capacitor 4 to the collector of transistor 2. The parameters of the reactive elements are related by a certain ratio. This makes it possible to provide a two-frequency mode in the CTP and to increase the steepness of the 4 sludge conversion.

Description

"

fe

si

h about

VI

FIG. i

The invention relates to a technique for temperature measurements.

The purpose of the invention is to increase the measurement accuracy by increasing the conversion steepness.

Fig, 1 shows a piezoelectric temperature transducer with a frequency output; Fig. 2 shows a typical spectrum of a harmonic multimode quartz resonator of an LC cut; FIG. 3 shows the temperature-frequency characteristics of the main (ftu), harmonic (fan) and most intense anharmonic overtones of the harmonic multimode quartz resonator of the LC cut; FIG. 4 shows the resonant characteristic of a reactive circuit connected between the collector and the emitter of the transistor, and the arrangement of the harmonics and anharmonic of the LC crystal slice on the frequency axis,

A piezoelectric temperature converter with a frequency output contains an amplifier 1 made on a transistor 2 with a common collector, a first phasing capacitor 3 connected between the base and the emitter of the transistor, a second phasing capacitor 4 connected between the collector of the transistor and the junction point of inductor 5 and capacitor 6, which are connected respectively to the collector and emitter of the transistor, a multimode temperature-sensitive quartz resonator 7 connected between the base and collector of the transistor, intramural resistor rezmstivny divider consisting of the resistors 9 and 10 and bypass capacitor 11.

Piezoquartz temperature transducer with frequency output works as follows.

The transducer uses a multimode temperature-sensitive harmonic quartz resonator of a Y-cut or LC-cut. Resonators of this type, as well as at-cut resonators, belong to piezoresonators with localization of thickness-shear oscillations and are multimode with intense anharmonic modes. Fig. 2 shows a typical oscillation spectrum of a harmonic quartz resonator LC-slice, where A is the ratio of the dynamic resistances on the fundamental oscillation and the corresponding harmonic or anharmonic mode; fmnp is the frequency of the oscillation mode, t, l, p is the number of hundred half-waves (or oscillating plate segments) along the y, x, and g axes of the quartz resonator, respectively; fin - basic oscillation; f of, f 131, fm are the anharmonic overtones of the fundamental oscillation, fan is the third harmonic of the fundamental oscillation; fsi3, f33i, fais are the anharmonic overtones of the third harmonic of a quartz resonator LC slice, which is sealed with helium filling.

In the described piezoquartz temperature transducer with frequency output, it is necessary to excite in two-frequency

the mode of oscillation of non-multiple frequencies fi and fa close to the natural resonant frequencies of the third harmonic fan with a positive temperature coefficient of frequency and its nearest intensive anharmonic fai5 with a negative temperature coefficient of the frequency of the quartz resonator 7 in the presence of also intense modes of the main oscillation fm and anharmonic fm, fi3i , fn5. Resilience

the dual-frequency mode in the converter is provided by suppressing the fundamental oscillation fm and its anharmonic fm, fiai, fns. This is accomplished by suppressing the inclusion between the collector and

the emitter of the transistor 2 is a reactive circuit consisting of a series-connected capacitor b and a parallel circuit including an inductor 5 and a capacitor 4. If the frequency of the series resonance

tosl

 + C2

0)

35

this reactive circuit is chosen equal to the frequency difference fp3 f315 f311, T.e.

fncrai fpa f315 - f 311

one

2lg% / ЦС1С + С2 and parallel resonance frequency

(2)

 steam:

(3)

This reactive circuit is chosen equal to twice the frequency difference fp3 fsis - fsn. T. e.

fnap 2fp3 2 (f315 - f311) 7

one

2rcVi C2

-.(four)

then the resonant characteristic of such a reactive circuit on the frequency axis with the modes of a temperature-sensitive quartz resonator at a frequency f0 of 26.5 MHz will look like as shown in FIG. 4.

From figure 4 it follows that between the frequencies fps and 2fp3, where the main oscillations of ft 11 and its anharmonic fm, fiai, fns are located,

the reactive circuit is inductive in nature and, therefore, for these frequencies the phase relations in the converter based on a capacitive three-point generator will not be fulfilled and these frequencies cannot be excited. For the frequencies of the third harmonic fan and its intense harmonic fais, as can be seen from FIG. 4, this reactive circuit is capacitive in nature and, therefore, for these frequencies the phase relations are fulfilled and the necessary condition for providing two-frequency oscillations of the converter occurs. A sufficient condition for the existence of two-frequency oscillations in the converter at the fan and fai5 frequencies is provided by suppressing the input of the nonlinear active element — transistor 2 of the difference frequency fp3 f3is - fsn with the help of the same reactive circuit consisting of capacitors 4 and inductance 5.

Relations (1) - (4) allow us to relate the parameters of the reactive chain elements to each other. Indeed, dividing (4) by (2), get

2 -

CLC + C2

F

C2

from here

four

CLC + C2 C2

or

CLC ЗС2

Determine Ca from (4), get

one

one

2 4Ji2 (2fp3) 2L 1 (f3i5-fan) 2L Substitute (8) in (7), get

CLC

l6 (f315-f31l) 2L

Thus, when selecting the parameters of the reactive circuit elements in accordance with (9), in the proposed piezoquartz transducer with a frequency output, some frequencies fi fan and fa fats are excited, depending on the measured temperature as follows:

fi-f3it f ° 3H + CTi (T-To); (YU)

f2 f315 f ° 315 + CT2CT-To), 01)

where That is the temperature at the reference point;

St1 - temperature coefficient of sensitivity of the f3n mode ();

St2 - temperature sensitivity coefficient MODES T315 ().

Due to the nonlinearity of the characteristics of the active element - transistor 2 in the output signal of the converter, in addition to

There are 5 main fan and fais frequencies, there are combination oscillations 2fp3 2 (fais-fan), fpa fais-fail. The second harmonic of the difference frequency, trz, is used as the output oscillation of the reuser.

10 which depends on temperature as follows:

feb.x 2fp3 2ff3is - fan) 2 f ° 3i5 + + CT2 (T-To) - Gai - CT1 (T-To)

(f ° 315 - f ° 31l) + (St2 + Crl) (T-To)

 2 (f ° 315 - f ° 31l) + 2 (St2 - St1) (T-To)

 2f ° p3 + 2Strz (T-To) 2 (f ° 3i5 - f ° 3i i) + + 2 (CT2-CTi) (T-To) 2f0p3 + 2Strz (T-To) f ° Bblx + Stvyh (T- To) (12) 20

and which is effectively separated by a parallel contour consisting of an inductor b of inductance and a capacitor 5 Considering that for quartz resonators LC-25, the following equality holds: 1

 (1i22). (13)

T311St1

30 The resulting coefficient of Stvykh tempoatur sensitivity is equal to

35

STV 2 (St2 - St1) -St1) -4.44St1

2 (-1.22 CT1

For a harmonic temperature-sensitive quartz resonator at a frequency of 26.5 MHz in the third harmonic, the temperature coefficient of sensitivity St1

40 1000Hz / ° C.

Therefore, in the proposed converter, the temperature sensitivity coefficient is 4440 Hz / ° C. Thus, significantly increased

45 the slope of the conversion characteristic due to the use of only one quartz resonator, the zero drift decreases and the long-term frequency instability improves, being detected,

50 mainly, by aging of the quartz resonator, aging leads to approximately identical drift frequencies of the fan and fais and to compensate for these drifts in the output frequency, a dual-frequency mode is used, which

55 dramatically improves the spectral composition of the output device.

Claims (1)

Piezozquartz temperature converter containing an amplifier on a transistor connected in accordance with the scheme a collector, a first phasing capacitor connected between the base and the emitter of the transistor, a second phasing capacitor, a multimode temperature-sensitive crystal oscillator connected between the base and the collector of the transistor, and a serial LC circuit connected between the emitter and collector of the transistor, characterized in that measurement accuracy by increasing the conversion slope, the junction point of the inductor inductance and the capacitor of the series LC circuit is connected to the collector of the transistor through The second phasing capacitor with the parameters of reactive elements selected from 3 CLC 3 C2  -f31l) 2L where fan and fais are harmonic and anharmonic overtones of a multimode temperature-sensitive quartz resonator; CCL and L are the capacitance and inductance of the elements of the LC circuit, C2 is the capacity of the second phasing capacitor. FIG 4