SU987528A1 - Hydrodynamic log - Google Patents

Description

(.5) HYDRODYNAMIC PAH The invention relates to a technique for measuring the speed of an object and is intended to measure the speed relative to the aquatic environment of ships and vessels. Hydrodynamic lags such as MGL or LG are widely used on ships and vessels, including static and total seawater pressure receivers, differential bellows apparatus and central: device C1 3. In a bellows apparatus, the hydrodynamic pressure (difference of total and static pressures) is converted into displacement stock. The measurement is carried out according to the compensation principle using the Ctli spring-loaded electromechanical compensation-measuring systems. However, these systems have considerable friction, backlashes and dead strokes in the associated elements, which leads to significant instrumental errors in the velocity measurement. The disadvantage is the long time constant of the compensation-measuring systems, measured in tens of seconds. Known hydrodynamic lag containing receivers and transducers of full and static pressure and recording device C 2. However, this lag has an instrumental error of 0.08–0.12 knots, and the time for full speed processing from 0 to 50 knots is 200 s. This is not enough for modern ships that require higher accuracy and speed of lags. The purpose of the invention is to improve the accuracy and speed of the hydrodynamic lag. To achieve this goal in the hydrodynamic lag, tunnel diodes included in the parallel arms of the bridge circuit, input

which is connected to a sawtooth generator, and the output is connected to a recording device made in the form of a time interval meter, and the generator input is provided with a current bias source.

The drawing shows a diagram of the hydrodynamic lag.

The magnitude of the peak current O of the tunnel diode is related to the magnitude of the overpressure P, as follows:

Uh

where JQ is the peak current value in the absence of overpressure; about - ratio proportional to OBTI.

The measuring circuit of the electronic hydrodynamic lag contains two tunnel diodes 1 and 2 placed in the full 3 and static pressure chambers, respectively, resistors 5 and 6, sawtooth generator 7, time interval meter 8, separation capacitors 9 and 10, and bias current source 11. All circuit elements

can be placed in one casing, 4

which, similarly to the well-known, can be called the central device.

Tunnel diodes 1 and 2 are included in parallel bridge circuits. Resistors 5 and 6 serve to balance the shoulders of the bridge. The lag circuit is constructed on arsenic-tunnel diodes, in which the peak current decreases with increasing pressure.

Let, at the initial moment of time, the current at the output of the generator 7 begins to increase linearly from zero to zero. Then the currents in the arms of the bridge circuit also increase linearly. When a tunnel diode 1 is reached in a shoulder — the resistor 5 has a current value equal to the peak current value for diode 1, the latter goes into a high voltage state. A positive voltage drop across the coupling capacitor 9 triggers the meter 8. In this case, the tunnel diode 2 is still in a low voltage state, because for it the peak current has a greater value than for diode 1, since

affects lower - static pressure.

With further increase of the current from the output of the generator 7, the magnitude of the current in the shoulder tunnel diode 2 - resistor

6 reaches the peak current value for diode 2. Diode 2 goes into a high voltage state and a positive voltage drop across dividing capacitor 10 stops the counting of the meter 8, while simultaneously turning the generator 7 into the initial state. 8 counts recorded by meter due to linearity

current rise from generator output

7 is directly proportional to the difference between the total and static pressures. Thus, the meter reading 8 is directly proportional to the hydrodynamic

pressure, i.e. the square of the speed of the vessel relative to the water. In this case, the time of a single measurement is determined by the rise time of the current at the output of the generator 7 from zero to reaching the tunnel diode 2 in the arm — resistor 6 of the peak current. Reduction of measurement time by increasing the rate of current rise at the generator output

7 is impractical because this reduces the relative accuracy of measuring the duration of the time interval and, ultimately, the relative accuracy of determining the speed

ship movements. To reduce the measurement time, i.e., increase the lag speed, a bias current source 11 is used. From the output of the source 11 to the bridge measuring circuit, a constant current is supplied such that in the shoulder tunnel diode 1 - resistor 5 the current does not exceed the peak current for diode 1 even at the maximum speed of the vessel. In this case, the time of a single measurement is reduced, because the peak current value in the shoulder is tunnel diode 2 — resistor 6 is achieved much faster (due to the constant bias current).

Claims (3)

The temperature compensation of the circuit is carried out by including the tunnel diodes 1 and 2 in the parallel arms of the bridge circuit, as a result of which the temperature changes of the current-voltage characteristics of the tunnel diodes 1 and 2 cancel each other out, since the transition time of the tunnel diode to the high voltage state is measured. m between the transition times of tunnel diodes 1 and in a high voltage state. The calculation of the speed of the trial on the duration of the time intervals and the introduction of the necessary corrections is not difficult and can be done both with the help of circuits on logic elements and in the ship's multi-purpose or specialized computer. Claims Hydrodynamic lag containing full and static pressure receivers and transducers and a recording device, characterized in that, in order to improve accuracy and speed, 8 tunnel diodes included in the parallel arms of the bridge circuit are used as pressure transducers; connected to a sawtooth voltage generator, and the output to a recording device made in the form of a meter for the duration of time intervals, and the input of the generator / generator is provided with a source current bias. Sources of information taken into account in the examination 1. I. Vlasov, V. Volpin, A. et. Hydrodynamic lags. L., Shipbuilding, 1967, C.9-U. 2. The same, p.220 (prototype) 3.Krivorotoe N.P. et al. Tunnel Diodes for Pressure Measurement, Instruments and Equipment of Experiment 1977, No. 2, pp. 266-227.