SU759987A1 - Digital meter of coplex resistance losses - Google Patents

Description

The invention relates to the field of electrical engineering, in particular to the field of measurement of parameters of complex values of alternating current.

five

Known devices for measuring the parameters of complex resistance, consisting of an operational amplifier, in the direct and feedback of which are included the measured complex resistance and the sample element, and phase-sensitive detectors (in-phase and quadrature), the output voltages of which are proportional. components of the object admittance FROM. one!

Constant voltages are converted into a digital code using analog-digital converters, and to obtain the relative parameter of the object (DB & capacitor, coil Q-factor) digital, logometers are used, the output code of which is proportional to the ratio of the voltages at the outputs of the phase-sensitive detectors. Such devices due to their simplicity and high speed are widespread. Their disadvantage is low; accuracy, caused mainly by the following reasons: error from non- 3 (

2

power supply stability, phase shifts of reference voltages of common-mode and quadrature detectors, phase shift caused by an “unclean” ¹ complex measure.

It is especially difficult to ensure the stability of phase shifts of reference voltages and an exemplary measure when operating the device in a wide frequency range, which has received much attention recently.

The closest to the proposed device is a capacitor parameter converter containing an alternating voltage generator connected to the input of a passive complex-to-converter converter active, consisting of an operational amplifier, whose 'direct' and feedback include measured and exemplary active conductivity. The output of the transducer is connected to the inputs of the in-phase and quadrature phase d 'detectors [2].

In the device-prototype phase detectors are made in the form of a series-connected phage-sensitive rectifier and a low-pass filter, designed for suppression, with a variable component of the output

759987

voltage, containing the frequency of power and multiples of it frequency. The reference inputs of the phase detectors are supplied with a supply voltage and a voltage shifted by 90 ° by the phase shifter. Outputs of phase detectors Connected to the inputs of a digital logometer.

In the absence of parasitic phase shifts of the reference voltages and with pure active conductivity C (or when the phase shift of the phase is accurately computed), the ratio of the voltages to high ^; phase 'detectors moves .......

where K _s · and k >> are the transfer coefficients of phase detectors.

The disadvantage of the known device lies in the low accuracy of measuring the loss of objects, due to the influence of the phase shifts of the reference voltages of the phase detectors and the instability of the phase shift of the reference measures. Accuracy is especially low.

when measuring objects with small or .....

big losses.

 The aim of the invention is to improve the measurement accuracy of the loss of the object'ta.

This goal is achieved by the fact that a digital measuring instrument of loss of the co-plex impedance, containing in series an alternating current voltage generator and / impedance converter into an alternating current voltage,. made on the basis of an operational amplifier with an exemplary measure in the feedback circuit, to the input of which a measured object is connected, in-phase and quadrature phase detectors, whose reference inputs are directly ^: but. and through a phase shifter, respectively, connected to the generator output, as well as a digital meter, the ratio of two constant voltages, made in the form of a series connection of an input switch, an integrator, a comparator, blocks of coincidence and a reversible counter, and a counting pulse generator connected to the second input of the block by a control unit coincidence, the outputs of which are connected to the control input of the input switch and to the third input of the coincidence unit, is additionally equipped with parametric a modulator connected in parallel with the measured object, two low-pass filters, two _______

high-pass filters, two amplitude detectors and two switches, as well as a phase-sensitive zero-organ and an additional coincidence unit. The yields of I and Q is the phase detector through a low pass filters' frequency are respectively connected to the first inputs of the first and second switches, the second inputs of which through the amplitude detector ¹ tori are connected to the inputs of a zero-phase-sensitive body and vyhbdam

g high-pass filters whose inputs are connected to the outputs of the in-phase and · quadrature phase detectors, respectively, and the output of the phase-sensitive null organ is connected via an additional matching unit to the control ^{υ to the} reversing counter input, the switch outputs are connected to the inputs of the input switch, and the control inputs of the switches and the second input of the additional coincidence unit is to the control unit.

The functional diagram of the device is shown in FIG. 1, the timing diagram of the work ”in FIG. 2.’

20 ·

The meter contains a generator of 1 · AC voltage, converter ^. Complex resistance to AC voltage, consisting of an operational amplifier 3, which

25 to the input of which the measured object 4 is connected, and the model measure 5, the parametric modulator b, the in-phase 7 and the quadrature 8 phase detectors, the phase shifter 9 are included in the feedback,

30 lowpass filter, filter 11

high-frequency amplitude detector; тор torus 12, first switch 13, low-pass filter 14, high-pass filter 15, amplitude detector 16, second switch 17, pha-sensitive zero — body 18, digital integrator: a logometer 19, consisting of a series-connected input switch 20, integrator 21, comparison lock, three-input coincidence block 23 and reversible counter 24, generator 25 clock pulses and control block 26, additional match block 27,

45

The operation of the device consider the example of measuring the tangent needle loss of a capacitor (C _x , o _x ). in the feedback of the amplifier 3 - conducted a bridge of 5 _o e ^{, <t} ,

A sinusoidal voltage generator 1 with frequency ώ feeds converter 2, At the same time, at the outputs of syn55. phase "7 and quadrature 8 phase

[detectors in the absence of 'parameter-. constant modulation appear. Modulator b

/ performs a periodic with hour ¢ 0: totoi 51 b symmetric modulation of the capacitance component of the object, alternately, connecting parallel to the object. ''positive ¹ ' * + С _М and '' negative '' eat ¢ 5 bone - -С _м . At the same time, at the output of phase5 759987 6

the output of the detectors appears voltage, shown in figure 2, where

and _{c +} = c _with and _and n + y) | soy

and _with _ = k _with and „(ι + y) | cos θ

And K- * ⁴ η Θ

0 _x

с'г * 5 <п8 _с ⁴ О

κα ^ ⁺ οο5θ _κ ·

sa (C _x * SdL1

% -Ί

nyas _x + s _m y |

Oo] £ d (C _to -C _m 11

at the input of the counter and the third cycle begins.

As is known, the number of pulses / recorded by the counter at the end of the second cycle is equal to '

5, ίβθ ₀

N - and ^t ° ° - ^to " ^to with ^so5b F ° -OD

° ' ^and k ~ K «<*> ev _k ' 1-ί £ θ _κ ί £ $ ' ¹ β? >

where K _i is the coefficient of proportionality.

15

Filters 10 and 14 of the lower frequencies, suppressing the variable component of the output voltage of the modulation frequency, produce constant components of voltages - and ₇ and ₈ , equal to 0 _σ and _κ, respectively. At the output of the high-pass filters, alternating voltages and _and ~ and and _<5 ~ are formed with a frequency of 51 and amplitudes

20

25

c, ₅ . ¹¹ _KkΜηΙ , _soy

Y and y, 5 detektiruyutsya · ^ Xia amplitude detectors 12 and 16, the outputs of which form a constant voltage

* g *

H | 2 ~ ^ vd ^ s ^ n ϊ '4а <п0 _с |

• ^and 16 '* ОЛ ^and н Н * У) ^ СО5 © to,

where K _hell - the transmission coefficient of the amplitude detectors,

A pha-sensitive zero-body 18 generates a signal that is detectable; the sign of the voltage phase forces relative to the voltage phase (Fs- (t, i.e. sign z! n $ _s ),. Voltage

through the switches GZ and 17 are fed to the inputs of the digital integrating logometer 19.

thirty

35

At the beginning of the third cycle, the switch 20 is shifted to the position a, and the switches 13 and 17 to the position b. Then, during the time T _o, is the integrator charged?

21 and ₁₂ , at the beginning of the fourth cycle (after the time T _o ) switch -20 is switched to position b and at the same time the control unit through the block 23 matches allows the passage of pulses from the clock generator 25 to the counting input of the reversible counter 24 and through the additional block 27 coincidence allows the passage of potential from the output of the photoelectric sensitive: a zero-body to the control input.reverse counter 24, which is thus established depending on the voltage phase (the sign

είη in _c ) in addition or subtraction mode. In the fourth cycle, the integrator 21 is discharged with a voltage of 0 "

The measurement process ends when the integrator is discharged to zero, fixed by the comparison unit 22.

The number of pulses, additionally received on the counter in the fourth cycle, is equal to

40 N. C - ^to p ^to with сβΙηβοΙ

^P 4 (6 ^to C ESR θχ 45

to _to

coaOc coa Θ _κ

ugg total number of pulses in the meter

The measurement process consists of four cycles (see figure 2). at the beginning of the 1st cycle switches 13, 17 / and

.20 are in position a. In this case, the integrator 21 over time. it is charged with voltage and _d . After the time T _o . The control unit 26 switches the switch '20 to the position b, simultaneously through the block' 23 coincidence, allowing passage of the assistant 24 set to the summation mode. Integrator

'pulses from the clock generator

25, to the counting input reversing

21 at the same time discharged voltage

-, and _to . At the time of discharge of the capacitor

£ to zero triggered unit 22 comparison, prohibiting the passage of pulses

50 Ν-Ν _ο -Ν ₄ δί§π e <§пб _с *

soav _with ί * йБ «« to ssoO _to Ιΐ-Ι ^ βχί ^ ⁸

So.

K _to cos9 _k '

The measurement error of cd £ in this case

7

759987

eight

that for small ίξδ 1/8} is significantly better than in the original, uncorrected transducer.

Note that the expression for Ed 8 does not include the value of C _m . This means that there are no special requirements for its accuracy and stability.

The device is applicable for measuring the loss of any objects (inductive, capacitive, resistors with parasitic capacitances or inductances), and the object and the model measure in the converter can be reversed. The structure of the device remains the same. The only requirement is that, in order to increase the accuracy of the “ ⁵ ”, a parametric modulation of the dominant component of the complex value should be carried out.

Compared with the known devices, the proposed one allows to measure the loss of alternating current (Un 8 Q) with high accuracy, especially objects with small and large losses. Understand The 25 requirements for the stability of phase shifts — the reference voltages of the phase detectors and the phase shift of an exemplary measure allow us to ensure the stability of the measured 30

For (the stability of the operational amplifier) and provide an opportunity to use the device to measure the loss of objects in a wide continuous frequency range. 35

Claims (1)

Claim Digital caliper losses complex impedance comprising ⁴⁰ successive post-connected voltage generator and an AC preobrazo.'vatol "integrated _resistance: AC voltage · iy configured based on operational amplifier 45 · with exemplary measure in the feedback circuit to the input. which is connected to the measured object, in-phase and quadrature phase detectors, the reference inputs of which are directly and through a .50 'cut phase shifter, respectively, are connected to the output of the generator, and ι also a meter of the ratio of two constant voltages, made in the form of a serial connection of an input switch, an integrator, a comparator, a coincidence unit and a reversible counter, as well as a generator of counting pulses, the output of which is connected to the second input of the coincidence unit and the control unit whose outputs are connected to the control the input of the input switch and the third input of the coincidence unit, characterized in that, in order to improve accuracy, the meter is additionally equipped with a parametric modulator, connected to the object being measured in parallel, two low-pass filters, two high-pass filters, two amplitude detectors and two switches, as well as phase-shifting tweeted zero-organ and an additional coincidence unit, the in-phase and quadrature phase detectors outputs are connected via the low-pass filters respectively to the first inputs the first and second switches, the second platoons of which amplitude detectors are connected to the inputs of a phase-sensitive zero-organ and to the outputs of the filters of the upper part one whose inputs are connected to the outputs of the in-phase and quadrature phase detectors, respectively, and the output of the phase-sensitive null organ through an additional match block under the keys to the control input of the reversible counter, the switch outputs are connected to the input switch inputs, and the control inputs of the switches and the second input of the additional match block connected to the control unit.