SU934785A1 - Acoustic level gauge - Google Patents

Description

This invention relates to the field of level measurement with ultrasound ultrasound.

Acoustic level gauges are known, which contain a generator of probe pulses G with a frequency-set1 WHICH circuit, made in the form of an electro-acoustic transducer connected to the output of the generator, and a receiving frequency-selective amplifier.

The disadvantage of such devices is the instability of the frequency of accumulation of probe pulses, which makes it difficult to isolate the useful signal from interference in a frequency selective amplifier.

The closest in technical essence to the present invention is an acoustic transducer containing a series-connected pulse modulator, a carrier frequency generator, an amplifier made in 9eid with frequency-giving, a node in the positive feedback circuit, and

output amplifier, to the output of which a reversible electroacoustic transducer and receiving amplifier are connected.

The disadvantage of this level gauge is that the operational safety is not high enough;

This is because, during operation of i, the frequency-setting chip of the generator and the frequency-selective circuit of the receiving amplifier can also relatively each other change the resonant frequencies as a result of unstable and frequency-dependent elements, which leads to a significant decrease in the amplitude of the reflected signal by output of the receiving amplifier, reduces noise immunity by increasing bandwidth.

The purpose of the invention is to increase the operational reliability of the gauge.

This goal is achieved by the fact that, in the proposed acoustic level gauge, the output of the receiving amplifier is connected to the input of the frequency reference node of the carrier frequency generator.

The drawing shows a structural diagram of the proposed acoustic level gauge.

The gauge contains a series-connected pulse modulator 1, a carrier frequency generator, which is an amplifier 2, whose frequency feedback circuit includes frequency-master unit 3, an output amplifier whose output is connected to a reversible electroacoustic converter 5 and a receiving amplifier 6. Output the amplifier 6 is connected to the input of the node 3 and thus this node is simultaneously included in the positive feedback circuit of the oscillator-carrier frequency and in the negative feedback circuit consequently included amplifiers i and 6, in which it is used as a frequency selective unit. Output 7 of node 3 is the output of the entire device.

Works proposed acoustic level gauge as follows.

Pulse modulator 1 periodically turns on a carrier frequency generator, consisting of amplifier 2 and. node 3 for a time equal to the duration of the probe pulse. The radio pulse produced by the generator of the same duration with the filling frequency determined by the parameters of frequency-setting node 3 enters the input of amplifier D. From the amplifier output, the radio pulse goes to the electroacoustic converter 5 and transforms the latter into an acoustic sounding pulse. The reflected acoustic impulse is received by the electroacoustic transducer 5, converted into an electrical signal and fed to the input of the receiving amplifier 6. From the output of amplifier 6, the signal goes to node 3. From the output of node 3, the highlighted interference signal corresponding to the reflected acoustic impulse goes further to the subsequent stages gain and measuring part of the gauge.

Since node 3 is included in the negative feedback of the output and receiving 6 amplifiers, their excitation in the gain mode of the useful signal is eliminated and node 3, without any switching, operates in the mode of forming the carrier frequency of the probe pulse and the frequency selection of the reflected signal. Node 3 is simultaneously included in the two feedback loops positive and negative, therefore, to operate amplifier 2 with a frequency setting circuit as a carrier generator, the condition

K, 0, K, K50 (L

where k, k,

K - gain factors

amplifier 2, output amplifier A and receiving amplifier b, respectively,

Oif ,, (transmission coefficients of frequency-selective circuit 3 at the resonant frequency in the positive and negative feedback loops, respectively.

The use of a single frequency setting node without any switchings to form a probe and highlight the reflected signal allows us to simplify the device in comparison with the known ones. The acoustic level gauge practically does not require tuning, and in any case, the frequency of the signals allocated by the receiving amplifier 6 strictly corresponds to the filling frequency of the probe pulses, and the reliability of the level gauge increases, first, due to the increased noise immunity. In addition, the bandwidth of the receiving amplifier 6 can be made arbitrarily narrowed, increasing the selectivity and, consequently, the reliability of the level gauge.

Claims (1)

ACOUSTIC LEVEL MEASURER containing a pulse modulator connected in series, a carrier frequency generator made in the form of an amplifier with a frequency-defining node in the positive feedback circuit, and an output amplifier, the output of which is connected to a reversible electro-acoustic transducer and a receiving amplifier, distinguishing with that, in order to improve operational reliability, in it the output of the receiving amplifier is connected to the input of the frequency-setting node of the carrier frequency generator.