SU122928A1 - The method of determining the sign of deformations in strain gauges at carrier frequency - Google Patents

Description

The subject of the invention is a method for determining the sign of deformations in strain gauge installations at a carrier frequency containing a cathode ray tube as an indicator.

A distinctive feature of this method is that the sign of the deformation is determined by the corresponding darkening of the half-wave of the image of the carrier signal on the screen of the tube. The shading is carried out by applying to the modulating electrode a cathode-ray tube of an amplitude-limited carrier voltage. This feature provides a more complete use of the screen of the indicator.

FIG. 1 shows the scheme of the proposed method; Fig 2-- the image on the screen of the cathode ray tube.

In tensometric practice, oscillographic tubes are usually used as an indicator, especially in multi-channel a-parameter, which allows simultaneous recording and monitoring of the indications of a large number of sensors. In the case of using equipment at the carrier frequency, it becomes necessary to determine the phase of the voltage of the signal taken from the measuring bridge (the sign of the measured value). The use of a conventional phase-sensitive valve ring circuit requires the use of direct current amplifiers after it. With fast switching of measuring channels. The arising non-stationary processes can distort the measurement results, especially with filters connected after a f-sensitive ring cell.

When implementing the proposed method, the modulated carrier frequency after the strain gauge., Measuring bridge / (Fig. 1)

arrives at the input of the strain gauge 2 and then into the deflecting plates 3 of the cathode ray tube 4. The electrical sinusoidal oscillations coming in simultaneously from the carrier frequency 5 of the carrier frequency turn into square wave oscillations and are fed to the modulating electrode 7 of the tube. As a result, depending on the sign of the deformation (phases for the sake of;), the lower or upper waveforms of the sinusoidal signal will be distinguished by the brightness of the tube screen.

If the sinusoidal voltage on the tube screen is partially darkened, the measurement accuracy will increase along with a clear definition of the sign of the measured value, since when measuring the amplitude of sinusoidal oscillation (proportional to the unbalance of the measuring bridge), the count is taken from the full (peak to peak) amplitude of the signal. In this way, the use of the tube screen is improved when emitting alternating processes.

The proposed method of registering the sign of the measured value does not require the use of ring demodulators, which is the source of additional errors in the measurement, as well as due to the inertia-free electron beam indicator, ensures accurate reproduction of non-stationary oscillations occurring when using high-speed switches.

Subject invention

The method of determining the sign of deformations in strain gauge installations at a carrier frequency with a cathode ray tube as an indicator, characterized in that, in order to more fully use the screen of the indicator, the sign of deformation is determined by the corresponding darkening of the half-wave image of the carrier signal on the screen of the tube, which By applying the modulating electrode of a cathode ray tube of an amplitude-limited carrier voltage.