SU555342A1 - Device for measuring rotational speed - Google Patents

Description

one

The invention relates to the field of measurement technology and can be used to measure rotational speeds on aircraft.

Induction type frequency sensors are widely used to measure the rotational speed.

Measuring devices are known that convert the period of the pulse of the sensor to a code or voltage 1.

A disadvantage of this device is the lack of calibration, which reduces the accuracy and reliability of the measurement.

It is also known a device comprising a sensor, an amplifier and an input pulse shaper, a control circuit forming the measurement inter shaft, a valve, one input of which is connected to the reference frequency generator, the second to the output of the control circuit, and the output to the counter 2 input.

The disadvantage of this device is the lack of means to check the performance before starting the measurement,

which leads to a decrease in the reliability of the measurement results.

The circuit of the invention is the implementation of an automatic calibration, which makes it possible to determine the operability of the device before starting the measurement.

This is achieved by introducing into the device a self-oscillating cg of a litivibrator, whose synchronization input is connected to the output of the driver, and the outputs are connected to the input of the amplifier of measured frequency pulses and to the input of the control circuit.

FIG. 1 shows a block diagram of the device: FIG. 2 is a timing diagram explaining the operation of the device in the measurement mode. FIG. 3 is a timing diagram explaining the pa6oiy device in the calibration mode.

The device contains a sensor 1, amplifier 2, Schmidg trchgge 3, control circuit 4, consisting of triggers 5 and 6, logic circuit OR 7, single vibrators 8 and 9, multivibrator 1O, valve 11, counter 12, memory register 13, digital analog transform 14, logic AND 15, generator reference frequency 16. The device has two modes of operation: measurement and calibration. Sensor 1 pulses, the amplitude of which exceeds the device response threshold, determined by the gain of amplifier 2 and the trigger level of Schmidt trigger 3, are fed to the synchronous input of the multivibrator 10 and to the counting input of the trigger 5, the oscillations of the oscillations of the vibrator and its setting to steady condition. Triggers 5 and 6 form a measuring interval equal to two periods of im ii g-pv sensor (see fig. 2a, b, c,). Trigger 6 controls the operation of valve 11. If there is a positive potential at the output of trigger 6, valve 11 is open and pulses of the reference frequency from the output of the generator 16 are fed to the input of counter 12 (see Fig. 2c, and k). The number of pulses transmitted to the meter is directly proportional to the duration of the measured interval. When the output potential of the trigger 6 is changed to negative, the valve 11 closes and the pulse of the reference frequency to the counter stops. Valve 11 remains in the closed state for the next two periods of the input signal. This time is used to carry out operations for transferring information from counter 12 to memory register 13 and then resetting the counter to O. The transfer and reset pulses are generated using the logic circuit OR 7 and one-shot 8 and 9. One of the inputs of the circuit OR receives a signal from the output of the multivibrator 10, to the second - from the output of the trigger 6. If there is a high potential at both inputs of the circuit 7, a low potential appears at its output, if there is a low potential at any of the inputs, a high potential appears l Since multivibrator 10 is in a steady state, which corresponds to the presence of a high potential at the collector of the transistor T (see Fig. 2e), the output signal of logic circuit 7 is determined by changing only the output signal of trigger 6, when switching tripper 6 from state 1 At the output of logical 7, a voltage drop appears (see Fig. 2a), which triggers the odiovibrator 8, which generates an information census pulse from counter 12 to memory register 13 (see Fig 2g), falling edge of the pulse When a single-shot 9 is started, it forms a reset pulse (see Fig. 2a), which sets all the bits of the counter to O. In the absence of pulses from the sensor, and also when the amplitude of the pulses is lower than the device response threshold, the multivibrator 10 operates in self-oscillation mode and the input to the amplifier 2 through the differential chain C2, P, D and C1 receives pulses that simulate the sensor signal. The frequency of the pulses of the multivibrator is 4-5 times less than the minimum frequency of the sensor, the amplitude of the pulses is sufficient to trigger the device. During the measurement interval equal to two periods of oscillation of the multi-oscillator, the reference frequency pulses are counted. If there is 1 in all bits of the counter, the output of logic circuit 15 And a negative potential appears, preventing further passage of the pulses of the reference frequency through valve 11. The unit state of the bits of the counter remains until the end of the measuring material while the one-shot 8 (see Fig . Зж) will not generate information from counter 12 to memory register 13, and the one-shot 9 will not reset the counter to O (see fig. 3). The pulses of the over-trip and the reset during the calibration process are formed twice during the period between two adjacent measuring cycles (see Fig. Zh, h). This is due to the fact that one of the inputs of the logic circuit OR 7 receives pulses from the output of the multivibrator 10, the frequency of which is 4 times higher than the frequency of the pulses at its other input (see Fig. Zh, h). In this case, the output of the OR circuit (see Fig. 3) between the two measuring cycles twice causes a negative voltage drop, which triggers the one-shot 9. Due to the presence of two Ioprecording pulses between two adjacent cycles, a single counter state is written to the memory register ( the first pulse) and the zero state of the counter (the second pulse.). Thus, in the process of calibration, the maximum minimum values of the code or MaKCH, faTij.TbTE and 1 minimum voltage levels alternate at the output of the device.

The presence of any other code values or voltages indicates a malfunction of the measuring device and the need to repair or replace it.

The values of the minimum and maximum levels of the output voltage are then used in the decoding to refine the measurement results.

Claims (2)

Invention Formula A device for measuring the rotational speed, containing successively connected sensor, amplifier and pulse shaper of the measured frequency, control circuit forming the measurement interval, reference frequency generator connected through the terminal to the counter input, a memory register, a digital-to-analog converter, characterized in that , for the purpose of automatic calibration of the device, what is introduced by the multivibrator, the synchronizing input of which is connected to the output of the driver, and the outputs are connected to the input of the amplifier pulse in the measured frequency and with the input of the control circuit. Sources of information taken into account in the examination: 1, USSR author's certificate No. 296138, M.C. G 08 C 9/04, 1969. 2.Turichin A. M, Electrical measurements of non-electric quantities. L., Energie, 1966, p. 441 (prototype). figure 1 ipLiS.Z- F zhshshzhd I