SU599165A2 - Resonance level meter - Google Patents

Description

The invention relates to a measurement technique and can be used to measure the level of liquid bodies with both emitters and dielectric and n-conducting media. In the mainstream avtse.se. No. 485321 described a resonant level gauge containing an excitation generator with a frequency modulator, the signal of which is supplied by a resonant level sensor with an amplitude detector, a memory device connected between the resonant sensor and a signal relay. Such a circuit does not provide the required accuracy when operating under conditions of operation. Personal disturbing factors (for example, temperature, vibration, shock, electrical noise). Moreover, & this scheme may turn out to be inoperable as a result of loss of stability under the action of intense perturbations. The purpose of the invention is to improve the accuracy of level measurement and ensure stable operation in conditions of perturbing factors. This goal is achieved by the fact that a pulse clock generator and a switch are additionally introduced into the proposed resonant sensor, and the output of the switch is connected to the input of the signal-relay. FIG. 1 shows a functional diagram of the proposed level gauge; in fig. 2 and 3 are essures that give a look at his work. The level gauge contains a generator of excited 1, the signal of which is supplied to a resonant level 2 sensor with an amplitude detector, a memory device 3 connected between the resonant sensor and the signal-relay 4. The output signal of the voltage signal generator is supplied to the frequency modulator 5. Clock generator impulses b is connected to switch 7, the control of the signal-relay. The sensor is energized by the generator 1, whose frequency is changed by the action of the modulating voltage. When getting the frequency of the generator 1 in the frequency band of the excited resonant

 2, the output voltage of the sensor increases and reaches a maximum when the frequency of the generator coincides with the resonant 4iacTOTofi sensor. Moreover, the voltage sticking to this voltage produced by the amplitude detector contained in the sensor repeats the shape of the resonant curve of the sensor (see Fig. 26). A memory device 3 is connected to the sensor output. When the generator frequency goes beyond the resonant frequency of the sensor, the memory device remembers the maximum value of the output voltage of the sensor. As the frequency of the generator 1 is removed from the resonant frequency of the sensor f, the output voltage of the storage device is determined once. the voltage of the filled voltage and the current value of the output voltage of the sensor increases. When the output memory voltage reaches the threshold, the avi-signalum relay d U signaling relay triggers and reverses the direction of change of the modulating voltage, and therefore reverses the direction of the generator frequency, which again approaches the resonant frequency of the sensor. When the generator frequency is equal to the resonant frequency of the sensor, the maximum voltage of the sensor is memorized again. Then again srabatshavt signum-relay and there is a reversal of the direction of modulation. As a result, auto-oscillations are established in the gage circuit, at which the frequency of the high-frequency generator changes by a small amount, l (see Fig. 2) around the resonant value. CHARACTERISTICS OF THE SENSOR.

Since the value of the resonant frequency of the sensor is related to the value of the medium level by the unambiguous dependence, and the frequency of the generator signal fluctuates with a small amplitude Lf around the resonant frequency of the sensor, level measurement reduces to determining the frequency of the generator signal in this level gauge. The output parameter of such a level gauge is the signal frequency, which is very convenient when using information transfer methods for large spaces and its registration. However, if desired, the frequency signal is easy to convert to analog.

In order to increase the level of measurement accuracy, increase the stability of the sensor operation under perturbing conditions, the search for extremum must be non-monotonous. The monotonous nature of searching for the resonant frequency of the sensor is provided by forced excitations of the reverse direction of the Stign frequency, which is performed by inputting the 6 pulses into the level generator. 7

Below, we consider the function of rovnemer in the conditions of MONETUGON so-called AI springs, which lead to a drift by means of the sensor's crying screw, since it is the drift of X stability. And the most dangerous is the upward drift. At a significant drift velocity of the resonance curve of the sensor, loss of stability is possible.

FIG. The image shows a resonant curve of the sensor and a transient process in a known level gauge.

- The transient process is depicted for the case of drift resonant} fivs sensor up.

FIG. 36 depicts the resonance curve; the sensor and the transition process in the proposed level gauge as well for the case of a drift of the resonant curve of the sensor up.,

 at that moment when the state of the circuit is characterized by the coordinates U and. {cm. FIG. For, point A}, perturbations start to act on the sensor, causing a mixing-reasion curve upwards. I Let at the moment of the beginning of the disturbances decrease the generator frequency. If the circuit were not acted upon, then with decreasing frequency, starting or point А 1. would decrease and “As a result, the signal relay would reverse, the frequency would begin to increase and VitS would begin to increase to extrextum. However, when exposed to intense monotonous motion, the movement to the extremum will occur 1 otherwise.

Suppose that at the time of the action of perturbation (point A) the frequency f decreases. During the time of frequency change from f to jtg and from to fj, the resonance curve, shifting vertically upward, takes the corresponding positions of i and E. As a result, now with decreasing f Un will increase, taking respectively g values of Un Ul. (see ig. For) .- tz. t ,,

Since now the voltage Un increases, the signal-relay will not reverse the frequency of the generator signal and the value of f will continue to decrease, i.e. G: move in the wrong direction, moving away from the extremum, i.e. loses stability. Similarly, the process will proceed if the moment when the disturbance begins to act, the state of the circuit is determined by a point on the right branch of the resonance curve (point A.) and the frequency increases.

To ensure the sustainability of the processes of the level gauge scheme, the search for extremum should be non-monotonic. For this in the BBV scheme