SU1654498A1 - Stress-measuring mechanism - Google Patents

Abstract

The invention relates to non-destructive testing of technological processes in the construction industry, can be used to measure mechanical stresses in prestressed reinforcement of reinforced concrete products and structures, and allows to increase the accuracy of measurements. The device contains an oscillation sensor 1, an active filter 2, a voltage divider 3, two smoothing filters, each of which consists of diodes 4 and 5, capacitors 6 and 7, and resistors 8 and 9 comparators 10 and II. trigger 12, counter 13 periods, generator 14 pulses, element 15, reversible counter 16, one-oscillator 17, switch 18, counter 19 pulses, element OR-AND 20, counter 21 delay, decoder 22, element OR 23 and indicator 24 2 il. Ё ШИ

Description

The invention relates to non-destructive testing of technological processes in the construction industry and can be used to measure mechanical stresses in prestressed reinforcement of reinforced concrete products and structures.

The purpose of the invention is to improve the measurement accuracy.

Figure 1 shows the functional diagram of the device; figure 2 - the timing diagram of his work.

The device contains an oscillation sensor 1 (differential), an active filter 2, a voltage divider 3, two smoothing filters, each of which consists of diodes 4 and 5, capacitors 6 and 7 and resistors 8 and 9, comparators 10 and 11, trigger 12, counter 13 periods, generator 14 pulses, element AND 15, reversible counter 16, one-shot 17, switch 18, counter 19 pulses, element OR-AND 20, counter-21 delay, decoder 22, element OR 23 and indicator 24.

The device operates on the principle of counting pulses of a highly stable frequency of a quartz oscillator 14 pulses, which fill several pairs of periods of oscillation of the armature.

Initially, a latching switch (not shown) switches on the device power supply, while the counters 13,16,21 and 19 are automatically set to O on the fault circuits, and the counter 21 is locked by the switch 18 and blocks the counters 13,16 and 21 through the OR element 23. The operator then performs shock or pinch excitation of vibrations of the reinforcement, sensor 1 is brought to it at a distance of 5-20 mm and a push-button switch 18 is manually pressed, which unlocks counter 21. One or two first pulse signals about the oscillation period coming from the trigger 12, change the state of the counter 21, which forms a delay in the counting of periods, after which it stops its account while simultaneously unlocking the inputs of the counters 13,16 and 21. In this way, the first one or two of the most distorted oscillation periods are skipped and then for several pairs of periods , counted by the counter 12, the pulses of the generator 14 are fed to the counter 19. after which the counter 13 self-blocks and through the element 15 blocks the operation of the counter 19.

During the measurement cycle of the device, the reversible counter 16 sums up the number of counting pulses from the generator 14 in odd periods and subtracts into even ones, performed a pairwise check of the following

after another periods of measured oscillations for mutual equality up to several higher bits of counter 16. The sign of inequality of oscillation periods (for example, with an accuracy of 0.5%) means that there is a strong interference in the measured signal, which distorts the measurement result. Check the status of the reversible counter

16 is carried out at the time of termination of every 0 even period using a single vibrator

17 (figure 2 - His pulse on the 6th diagram). If at this moment a certain number of high-order bits of counter 16 are not zeroed, the OR-AND element 20 transmits the His pulse generated by the single-oscillator 17 to the discharge circuits of the counters, having wrapped their contents. In this case, the measurement process automatically continues until the specified number of periods is equal to 0 pairs. In the case of pairwise equality of the periods, the HIS pulses during the measurement process do not pass to the fault inputs and the counter 13, having fixed a predetermined number of periods of reinforcement oscillations, with its first output blocks the passage of the generator 14 pulses to the counter 19, which fixes the number of these pulses. The contents of the counter 19, characterizing the duration of a specified number of periods

0 oscillations of the armature of the main current, is deciphered by the OR-and element 20 and is output to the digital multi-digit indicator 24. When you release the push-button switch 18, the counters are reset.

5 in O, and the digital display of the indicator 24 goes out.

The selection of oscillation periods (the formation of time marks) is performed as follows.

0When the sensor 1 is installed at a distance

5-20 mm from oscillating reinforcement, the oscillation signal is filtered, amplified and fed to the inputs of each of the comparators 10 and 11 through two channels: directly (signal

5 I2 in FIG. 2), through a voltage divider 3 and diodes 4 and 5 (respectively, I4 and IB signals in FIG. 2).

Passing through the second channel, the oscillation signal is converted into an I4 signal (Hs),

0 and its amplitude is fixed by a capacitor 6 (7). The comparator 10 (11) forms the pulse Iv (Ie) by the result of the comparison. the front of which captures the beginning of periods. Trigger 12 is set to 1.

5 only by the comparator 10 and reset by O by the comparator 1 1, therefore, during the positive half-wave of the oscillation signal, trigger 12 switches to 1 on the leading edge of the first pulse, the comparator only once. Everything

other (false) pulses will not affect its state. Examples of spurious pulses are shown by a dotted line in FIG. Similarly, during the negative half-wave action, trigger 12 is set to O only once over the first half-period pulse of the comparator 11.

False switching trigger 12 is possible only with a large level of interference. amplitude comparable with the first harmonic of oscillations (figure 7a in figure 2). Pairwise period inequality is possible with periodic distortion of the oscillation waveform (Diagram 7c in Fig. 2), with a high Beat level, exposure to lower frequency interference than the first harmonic of oscillations, for example, when an operator’s hand shakes, etc. In this case, the oscillation signal test circuit comes into operation, automatically resetting the false readings until the level of interference decreases and enters the deadband.

The frequency of the measured oscillations fK is determined by the formula

“--V.

where tV is the frequency of the generator 14;

n is the number of 13 oscillation periods measured by the counter;

K - the number of pulses measured by the counter 19.

Further, the stress in the valve is calculated using the well-known formula

.2- (l f- 12.5 u) 2,

where I is the free length of the reinforcement between the stops of the form or stand;

d - diameter of reinforcement.

Thus, the introduced function of checking the result of measurements, consisting of an even number of oscillation periods for the pairwise equality of the durations of the periods, makes it possible to significantly increase the noise immunity of measurements and, therefore, the measurement accuracy

Claims (1)

Invention Formula Voltage Measuring Device mainly in reinforcement of reinforced concrete structures containing an oscillation sensor connected to the input of the active filter, the output of which is connected to one the inputs of the first and second comparators and the input of healers, the outputs of which are connected to other inputs of the comparators through the corresponding smoothing filters, whose outputs are connected to the corresponding trigger inputs, a pulse generator that is connected to one of the inputs of the And element, the other input of which is connected to one of the outputs of the period counter, one of the inputs of which is connected to the trigger output, the output of the And element connected to one of the inputs of the pulse counter, the output which is connected to an indicator through a decoder, and a switch, characterized in that increase the accuracy of the measurement; a reversible counter, one-shot, an OR-AND element, a delay counter and an OR element are entered into it, and one of the NPDSB reversible counter is connected to the generator pulses, another output of the period counter is connected to another input of the reversible counter and to the input of the one-shot. The switch is connected to one of the inputs of the delay counter, the other input of which connected to the trigger output, the outputs of the reversible counter and the one-shot are connected to the corresponding inputs of the OR-AND element. the output of which and the output of the delay counter are connected to the corresponding inputs of the OR element. you:; - g of which is connected to another input of the pulse counter, to another input of the period counter and to the corresponding input of the reversible counter. .U2 L / us b C Uis 4f47 r / x FIG. 2 d