SU781704A1 - Strain-gauge device with square supply voltage of bridge - Google Patents

Description

(54) THERMAL DEVICE WITH RECTANGULAR VOLTAGE POWER BRIDGE

one

The invention relates to a measurement technique, in particular, to a strain gauge apparatus at a carrier frequency with a rectangular voltage supplying the measuring bridges.

Known tensometric apparatus with a rectangular power supply voltage for bridges, comprising a clock pulse generator, a frequency divider, a demodulator driver, a power supply voltage shaping device for the measuring bridge, a first amplifier, a key device, a second amplifier, an inverter, a demodulator, a filter, and an output amplifier CH-15

In this apparatus, the influence of spurious emissions on the fronts of the measured voltage is greatly reduced by gating, which is performed by a key device placed between the first and second amplifiers.

The disadvantage of this equipment is the absence of galvanic separation between the measuring bridges 25 and the inputs of the equipment, which leads to a decrease in the noise immunity of the equipment with respect to the interference occurring between the ground points of the equipment and the object of strain gauge, 30

remote from each other sometimes hundreds of meters. With significant energy saturation of modern measuring rooms and stands, the level of interference between the grounding points of the object and the equipment reaches a value that makes it difficult to measure low level signals.

The known apparatus for measuring deformations and temperatures, comprising a master oscillator, a power supply device for bridges, measuring bridges, an input transformer, an amplifier, key and output devices, in which galvanic isolation between the measuring bridges and equipment is implemented through the use of an input transformer with an ungrounded primary winding 21 .

Claims (2)

The disadvantage of the device is low accuracy, since the capacity shunting the shoulder of the crust will vary considerably, this will lead to errors in measurements, which is very difficult to measure, since the duration of the transition process depends on the output impedance of the bridge, the inductance of the transformer, input cable capacitance, etc. The purpose of the invention is to improve the measurement accuracy. .. - --- {jQj.;, jg-j {-jj- -jj- circuit is achieved by the fact that a teleometric device containing a series-connected master oscillator, a bridge power supply unit, a measuring bridge, an input transformer, an amplifier, a key and the output blocks are equipped with a PCR connected in sequence and a second terminal block, the input of which is connected in parallel to any of the windings of the input transformer, and the input form to the output of the master oscillator. FIG. Figure 1 shows the structural scheme of the proposed tensometric device with a rectangular voltage to supply the bridge; in fig. 2 - stress diagrams. The strain gauge device contains the master oscillator 1, one output of which is connected through the power supply unit 2 of the bridge with a diagonal. 3 power bridges. The second output of the master oscillator is connected to the key block 4 and the driver 5. The measuring diagonal of the bridge is connected to the primary winding of the input transformer b, and a second key block 7 connected to the output of the driver 5 is connected one of its windings (for example, secondary one). The amplifier 8, the first key block 4 and the output block 9 are connected in series to the secondary winding of the transformer. The operation of the circuit can be illustrated with voltage pads (see Fig. 2, ep. 1-6). in the master oscillator 1, the square-wave pulses are generated (ep. 1), which are then fed to block 2 of the PGs and Bridges, where a logical division of the generator frequency to the value of the carrier frequency and amplification of the received voltage Tp is achieved (ep. 2). In addition, control pulses of key block 4 (ep. 3) and forcing 5 (ep. 4) are generated in the master oscillator. From the output of the bridge power supply device, voltage is applied to the diagonal power supply of the bridge. The signal from the output of the measurement bridges (ep. 5) is fed to the input transformer 6, and by the time of parasitic emission on the voltage fronts from the bridge, one of the MOTOjf transformers (in Fig. 1 secondary) closes up at the second key block 7 and remains in this state until the end of the transition process. This significantly reduces the self-induction voltage across the primary winding of the transformer and reduces the duration of the parasitic surge by reducing the constant charge time of the parasitic capacitance in the bridge. The second key block is controlled from the generator 5. From the transformer output, the signal goes to the amplifier 8 and then to the first key block 4, which is controlled by pulses from the master oscillator 1. The control pulses of the first key block overlap the control pulses of the second key block and are arranged symmetrically with respect to the voltage fronts of the power supply of bridges in order to exclude switching voltage surges, formed during the operation of the second key device, and mind nshat error due to the finite inductance value of input transformer primary winding when changing the output impedance of the bridge. From the output of the first key block, the measured signal (ep. 6) goes to the output block 9. The obtained results showed that the introduction of strain gauge equipment with an input transformer can significantly improve the measurement accuracy while maintaining high noise immunity inherent in electroplating equipment, input and amplification circuits . The invention of the Strain gauge device with a direct voltage of the power supply of the bridge, containing in series connected generator, power supply unit of the bridge, measuring bridge, input transformer, amplifier, key and one-way blocks, characterized by the fact that it is equipped with sequentially connected driver and the second key unit, the input of which is connected in parallel to any of the windings of the input transformer, and the driver input - to the output of the master oscillator. Sources of information accepted. Attention in the examination 1..Prospekt firm Brühl and Kjерr Tenzo Indicator 1526. 2. Veklemishchev A.I. and others. Sat. work on measuring and computing systems to study the aerodynamics, dynamics and strength of aircraft. TsAGI, issue. 1599, 1977. ./ WLS1