SU1695140A1 - Device for measuring substance level - Google Patents

Abstract

The invention relates to a measurement technique and can be used for non-contact measurement of the level of various substances. The purpose of the invention is to improve the measurement accuracy. Controlled substance 1 is probed by waves modulated in frequency, the received reflected waves, due to their time delays during forward and backward propagation, have a frequency different from the frequency of probing waves at any time. Here, multiple consecutive passage of the forward and backward paths by the waves takes place, which makes it possible to repeatedly increase the measurement accuracy. 4g. This antenna directs the received antenna 5i waves towards the controlled substances 1. The receive-radiation operation is repeated many times, for which the circuit contains N transmit and N receive antennas. The wave from the last receiving antenna is fed to the mixer b, to the other input of which the reference signal is fed from the generator and then to the recorder 2 or less. (L o you ate

Description

t, 5 -Sh ... I I

t I f

 W

W / H

/ ft / ft ff /

2

The invention relates to a measuring technique and can be used for non-contact measurement of the level of various substances, can be used to measure the level of a liquid metal in technological containers of metallurgical production, the level of liquid and granular substances, regardless of their electrophysical parameters.

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

Figure 1 (a, 6) shows the graphs of the time dependence of the frequency f (t) of the probe and the received waves; Fig 2 is a diagram of the device.

The device contains controlled substance 1, generator 2 of frequency-modulated oscillations, directional coupler 3, transmitting antennas 41,42, ..., 4,

receiving antennas 5i, 525m, mixer 6

frequency recorder 7.

The device works as follows

Controlled substance 1 is probed by waves (electromagnetic, acoustic), modulated in frequency according to an asymmetric (figure 1, a) or symmetric (figure, 1.6) sawtooth law within the range of its deviation A f. Due to their time delays during forward and backward propagation, the received reflected waves have a frequency that is different from the frequency of the probing waves at any time t (see Fig. 1, a, b, dashed lines). The difference (difference) between these frequencies — the beat frequency fe — is expressed by the following formula

, 2kNAfFM ,,,

fe z, (1)

where FM 1 / Tm is the modulation frequency;

1 and k 2, respectively, for asymmetric and symmetric frequency modulation;

Tm is the modulation period;

c is the phase velocity of the waves.

Here there is a repeated successive passage by the waves of the direct (to the object) and the return trip, as a result of which they travel the effective distance 7ff NZ, where N corresponds to the number of soundings of the object (the surface of the monitored substance). Such an effective removal of this surface from the antennas actually makes it possible to multiply increase the measurement accuracy. The fixed value of the error D7 definition of the level is

AZ -r, r

(2)

which is N times less than in the case of single sounding.

The source of frequency-modulated waves is a generator of frequency-modulated oscillations 2, connected via

the main arm of the directional coupler 3 with the transmitting antenna At. The waves emitted by it are received by the receiving antenna 51, which is connected to the transmitting antenna 4i. This antenna re-guides the received 5t waves to the side of the monitored surface 1. The receive-receive operation is repeated many times, for which the circuit contains N transmit and N receive antennas, the first transmitting antenna 4i being connected (via a directional coupler) to the generator 3, and the last receiving antenna 5y is connected to one of the two inputs of the frequency mixer 6, to the other input of which through the side

the arm of the directional coupler 3 is supplied with the reference signal from the generator 2. The intermediate receiving antennas and the transmitting antennas corresponding to each of them are connected in pairs: 5i

and 42, 52 and 4h ,, 5s-1 and, as a result, the re-radiation of received waves in each pair of interconnected antennas occurs. This leads to a cumulative time delay t3N, depending both on the measured distance (level} Z. and on the number of M soundings: ta, rflet3 2Z / C is the delay time for a single sounding,

When taking measurements should

only the corresponding receiving antenna should receive reflected waves. This can be achieved by using antennas with a narrow radiation pattern or / and if possible

at the mutually exclusive arrangement of antennas above the surface of the controlled substance.

The device can be implemented using electromagnetic waves of various frequency ranges (microwave, optical ranges), acoustic waves and the corresponding functional elements of the circuit corresponding to these waves and frequency ranges.

Claims (1)

Invention Formula A device for measuring the level of a substance, containing a frequency-modulated oscillator, a directional coupler, transmitting and receiving antennas, a frequency mixer and a recorder, with than the generator output is connected through the main arm of the directional hole of the coupler to the transmitting antenna, and through the side arm to the first input of the frequency mixer to the output of which the recorder is connected, characterized in that, in order to improve the measurement accuracy, it contains / ft Y s H H Tp FIG. 1, and There is additionally at least one pair of transmitting and corresponding receiving antenna, with the receiving antenna of the previous pair connected to the transmitting antenna of the subsequent pair, and the last receiving antenna is connected to the second input of the frequency mixer. / / ; B / 2 FIG. 1.5 Tm