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the Analysis of metrological characteristics akselerometricheskih converters

According to metrology substantive provisions, the lapse akselerometricheskih converters is classified on casual and regular. Thus the reason of emersion of casual lapses are the features of a hardware representation leading to presence of functional failures of electronic components, the a part converter.

The reason of origination of lapses of the given class-room is failures and instability of a supply voltage, noise on an exit of amplifiers, features of service conditions (thermal and mechanical affecting). The regular lapse, as a rule, is defined most
Precisely in engineering specifications on concrete akselerometrichesky the converter also is a consequence of affecting of technology factors and temperature perturbations at known parametres of a leakage of thermal processes in designs of sensing elements [50, 51].

On the basis of the analysis of digital accelerometres, the most widespread in the market measuring akselerometricheskih converters, a number of the lapses influencing accuracy of measurements and demanding the account at their practical application in goniometricheskih measuring systems has been revealed. In table 2 lapses which can be eliminated at gauging conducting are resulted.

Table 2 - the Lapses eliminated by gauging

Accelerometre model Null lapse, mg The resulted lapse of null, % Multiplicate lapse, %
MMA7450 250 3,2 -
MMA7660 64 4 8
MMA7455 330 4 10
ADXL345 150 2-4 10
SMB380 60 1 -
LIS202DL 40 2 10
LSM303DLM 60 - -
LIS331DLH 50 1,7 7

Thus the multiplicate lapse is a problem which in traditional sensing transducers dares at the expense of application of difficult compensation methods in devices of formation of a starting signal of the measuring converter [50]. It is necessary to notice, that application fazometricheskogo a principle of formation of a signal allows to eliminate completely a multiplicate lapse akselerometricheskih converters [51]. Especially it is necessary to gate out a lapse called by a temperature regime of accelerometres (table 3).

Table 3 - Temperature lapses of accelerometres

Model

The accelerometre

T emperaturnyj null drift, mg ∕ ° C Temperature instability of a conversion coefficient, % ∕ °C
MMA7660 1,5 0,01
ADXL345 1 0,02
SMB380 1 -
LIS202DL 0,5 0,01
LSM303DLM 0,5 0,01
LIS331DLH 0,6 0,01

Temperature measurement is applied to the account of temperature agency in high-precision akselerometricheskih sensing transducers, with possibility of the further application of algorithms of temperature correction [52, 53].

In table 4 metrological parametres of accelerometres which define sensitivity of the sensing transducer on axes of measurements and the lateral lapse defined in width of the diagramme of directivity of the sensing transducer are resulted.

Apparently from the resulted data, to the greatest numerical components of the general extent of the error of accelerometres the lapse of null and a sensitivity lapse - on 10 % and 6 %, and as a lapse of the transverse sensitivity (2 is... 5 %) and nonlinearity of the accelerometre (0,5... 2,5 %). Also significant deficiencies of the resulted inertial sensors is rather low accuracy and zashumlennost a starting signal drift of displacement of null [53].

Table 4 - Metrological parametres of accelerometres

Accelerometre model The permission, mg Lateral sensitivity, % Nonlinearity, % from FS
MMA7450 15,6 5 1
MMA7660 21,33 1 -
MMA7455 15,6 5 1
ADXL345 3,9 1 0,5
SMB380 4 2 0,5
LIS202DL 18 4 -
LSM303DLM 1 - -
LIS331DLH 3,5 4,2 1

It is necessary to gate out multiplicate lapses akselerometrichesikkh converters in the capacity of the separate class-room of the lapses, making the basic impact on stability of measuring branches of the converter [54].

In the theory of lapses the multiplicate lapse is defined as the determined regular deviation of indications of the measuring gear, having the long period [55, 56]. The reasons of origination of a multiplicate lapse are, in the core, feature of conditions of medium of maintenance (temperature instability, instability of a source of feeding voltage, etc.) [50].

Thus, the multiplicate component of a lapse of measurements depends as on magnitude of a projection of seeming acceleration on a nominal axis of sensitivity of the accelerometre (a scale factor lapse), and from magnitude of a projection of seeming acceleration on a plane, orthogonal axes of sensitivity of the accelerometre (a lapse of an error signal of axes).

During the analysis of the lapses, making the most essential impact on tochnostnye parametres akselerometricheskih converters, have been revealed following regularity:

- Observed accelerometres have essential enough initial lapse of null demanding additional gauging (1-4 %);

- There is an initial lapse of sensitivity (8-10 %);

- Presence of lateral sensitivity (1-5 %) means, that at changes only on axis H, also there is a little change on a Y-axis;

- Presence of a lapse of a digitization (7-9,5 %), originating in the course of transformation and a data transfer.

In the capacity of solutions of a problem of raise of stability of measurements to agency of multiplicate lapses have found wide application the compensation methods which essence consists in application of a source of an alternating current in devices of formation of a starting signal of the accelerometre with the subsequent reinforcement of the detected starting signals in amplifiers
Differential type. Raise of accuracy and instability elimination in this case is carried out by means of turning on in a measuring circuit of the variable compensatory resistor, one of which contacts is connected to an entry of one of rectifiers, another - with an additional entry of the differential amplifier [57].

Generally, observing branches of the measuring converter (an axis of sensitivity of the accelerometre) the voltage of signals formed for each of a component, will have the following appearance:

Where - instability factors; U0 - a supply voltage.

Hence, function of formation of a lapse of transformation of parametres of accelerations in slope parametres opisyvaetsja on the basis of expression: where - real value of a slope.

Drawing 7 confirms the fact of direct dependence of the maximum error signal of branches of the measuring converter of parametre of an inclination at the maximum value of a multiplicate lapse.

Drawing 7 - Dependence of an error signal of branches of the measuring converter on a multiplicate lapse

Hence, the multiplicate lapse cannot be compensated to the full, for its partial elimination, in the core, compensation methods [58] are applied.

1.4

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A source: GRECHENEVA ANASTASIYA VLADIMIROVNA. PHASOMETRIC METHOD OF MONITOMETRIC CONTROL ON THE BASIS OF ACCELEROMETRIC CONVERTERS. Thesis for the degree of candidate of technical sciences. Belgorod - 2019. 2019

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