SU742784A1 - Device for monitoring concrete solidifying processes - Google Patents

Description

one

The invention relates to measuring the state of the properties of media in the process of solidification, structure formation, polymerization, etc. in those cases when the controlled medium changes its properties from conducting to dielectric in time. It can be used for non-destructive testing in the construction and chemical industry.

The device is based on measuring the equivalent tangent of the dielectric loss angle of a system consisting of a capacitive transducer, a controlled medium, and a dielectric strip (or gap) between the transducer and the medium.

A device is known in which a measuring circuit with a shunt diode is made in the form of an oscillator, the anodic oscillating circuit of which contains a capacitive transducer 1.

Parallel to the oscillatory circuit, a shunt diode is connected, to the cathode of which a reference voltage is supplied from an additional source. The microammeter is connected in series with an oscillating circuit inductance coil. In parallel, microammeter

included capacitor. The measured current is proportional to the dielectric loss in the oscillating circuit.

The disadvantage of this device is that the inclusion of a microammeter directly into the oscillating circuit complicates its circuit and degrades the quality factor of the circuit, which leads to a decrease in sensitivity

10 device.

The closest technical solution to the data of the invention is a device for monitoring the processes of hardening of concrete, a self-oscillating measuring oscillator made according to the three-point capacitive scheme, an effective transducer, an amplitude detector, a time delay element, registering device 2. Capacitive

20, the converter is an element of the load circuit of the autogenerator. At the end of the main process of structure formation, the moment when the signal value passes through

25 extreme point that indicates the end of the hardening of the concrete and turns off the sources of warming up.

Despite the possibility of fixing the end of the main processes

30 of the structure formation of concrete, the device has a low accuracy of determining the moment of occurrence of an extremum. This disadvantage is associated with the fact that the slope of the extremum curve has a very small value depending on the equivalent loss tangent angle tgS from the loss tangent angle tgcJ.

The purpose of the invention is to improve the accuracy of determining the end of the main processes of structure formation of concrete

The goal is achieved by introducing a frequency detector into the device, a multiplying unit in a feedback circuit with direct current and a time delay element, the input of the frequency detector being connected through a coupling capacitor to the collector of the auto-oscillator transistor, the output of the frequency detector is under-. The key is connected to the first input of the multiplication unit and also through the time delay element in the feedback circuit to the base of the transistor of the autogenerator, the second input of the multiplication unit is connected to the output of the amplitude detector, and the output of the multiplication unit is connected to the input of the recording device.

FIG. 1 is a schematic diagram of a device for controlling the process of hardening of concrete; Fig.2 temporary dah.agrammy.

The device consists of a measuring oscillator 1, an amplitude detector 2, a frequency detector 3, a multiplication unit 4, elements 5 and b of the time delay, a recording device 7.

Measuring oscillator 1 is assembled on a transistor 8 according to a common base circuit, with capacitive feedback and contains resistors 9-11 and capacitors 11-14, which ensure the establishment of the oscillator mode at constant and alternating currents, separation capacitor 15, an oscillating circuit consisting from inductance 16 and capacitive converter 17, between the plates of which and the controlled medium 18 there is a dielectric pad 19, or there is a gap.

The device works as follows.

; During the hardening process, the properties of concrete vary from conductive to dielectric. At the same time, the equivalent tangent of the loss angle t.gey (and, respectively, and (tgO) at the output of the amplitude detector) of the transducer I-7 - gasket 19 – beToH 18 varies with time as shown in FIG. 2a, and the capacitance transducer system equivalent capacity is a dielectric strip concrete (and, accordingly, Ug (C) at the output of the frequency detector of the same

the system is changed as shown in Fig. 26. The initial amplitude value of the high-frequency voltage on the collector of the transistor 8 of the measuring auto-oscillator is determined by the value of tg (j, and, accordingly, by the quality factor of the oscillating circuit 16, 17. This voltage is through the separation capacitor 15 is fed to the input of the amplitude detector 2, and then after detecting Uj to the first input of multiplication unit 4. The voltage U, at the output of frequency detector 3, depends on the capacitance C5, which during the concrete hardening process begins to decrease only when the extremum is reached in the characteristic t: g03 (t). This voltage is applied to the second input of multiplication unit 4, as well as to the input of the DC feedback element 5 to the base of the transistor 8. The effect of this feedback z leads to a more dramatic decrease in the voltage amplitude at the collector when the tgO (t) characteristic passes through the ectremum, as shown in Fig. 2c (i). After multiplying the voltages i.and i and fed to the inputs of the multiplication unit 4, at its output the voltage of the Zu is formed, the change of which in the time of the display but in fig. 2g. The changes in U3, (t) in the extremum region are characterized by a much greater steepness than in the U. characteristic. (T which leads to an increase in the accuracy of determining the moment of occurrence of the extremum. To eliminate false alarms due to interference, the voltage 0 (t) is applied through the element 6 of the delay time to the logger 7

Thus, an increase in the accuracy of determining the end of the main processes of structure formation of concrete is achieved by simultaneously using two signals and {tg) and (Cj) to increase the steepness of the right branch of the output signal and (t) to the recorder.

Claims (2)

1. Momot E.G. Shunt diode generator and its application. Gosenergoizdat, 1959, p. 17 2. USSR author's certificate No. 362242, cl. G 01 N 27/22, 1971 (ProType). (/,) u (c,) 6 uj Vy - u u