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oil fine of ultrasonic ergonomics default

oil fine of ultrasonic ergonomics default
Insufficient first step: a new use of the method of ultrasonic testing oil density measurement method with respect to the two previous signal generating system sends out a pulse signal, by shaping, frequency division, amplification gave ultrasonic transducer into a square wave the transmitting end of generating ultrasonic longitudinal wave while starting the counter starts counting, ultrasonic propagation analyte in the oil to be subjected to a certain amount of time, when the signal generating system sends this pulse after a certain time reaches the receiving end of the transducer, a counter stop counting, and apply to the microcontroller interrupt, this time under the counter and arrive at the receiving end of the signal after the number of integer cycles.

This instrument uses CT54/74AS867 as a counter, which has eight output ports Q0 ~ Q7, a 16MHz pulse signal input from the input terminal, the counter pulse falling edge count for Q2 port is 8 16MHz pulse frequency and, thus, obtained a 2MHz transducer excitation pulse. Q3 to Q7 of the port's output indicates a 2MHz Q2 port output of the excitation pulse number of cycles. Finally, therefore, simply read out the port output of Q3 to Q7 can know the number of whole cycles experienced by the ultrasound in the oil to be tested.

Step 2: signal generating system continues to issue a pulse signal (sine or cosine) sent to the transmitting end of the ultrasonic transducer to generate ultrasonic longitudinal wave, the counter is not counting, is still retained in the previous step a note of the number of cycles. After the receiving end receives the signal, and the signal after filtering, shaping, amplified and fed to the comparator for phase comparison with the original signal, this phase difference is converted into time added to the integer multiples of the same first step cycle time can obtain the actual time difference. This part of the circuit is constituted by a comparator, and 12-bit A / D converter chip, wherein the comparator with the chip is a 74HC4046 phase monitor output, the comparison between the waveform received by it can be achieved with the original waveform (2MHz waveform) The output of the comparator is 0 ~ +10 V, when the phase difference of 0 degrees, the output is low 0V; when the phase difference is 360 degrees, the output is +10 V high.

AD574A chip A / D converter is used, it is converted into a voltage signal of 0 ~ +10 V out from the comparator reflect retardation 000H ~ FFFH digital signal is then sent for the CPU reads. Join the A / D converter can greatly improve the measurement accuracy.

After A / D conversion is equal to the phase of 0 ~ 360 ° Average divided into 4096 parts, a precision of about 0.088 °. The accuracy of the instrument which can be drawn: 0.5μs × 1212 = 0.122ns = 1.22 × 10-10s (3) of formula (3) in the 0.5μs 2MHz ultrasonic cycle, i.e. one cycle is divided into 4096 parts. Taking into account the actual work in the A / D converter's output low is beating, the detection accuracy of the actual time at least up to 1ns (1 × 10-9s). If the frequency of the ultrasonic waves is increased, the increased number of bits of the A / D converter of the time the accuracy of detection can also be doubled.

In the present instrument, the design of the probe portion of the structure of the piezoelectric ceramic wafer bonding in a hollow cover body, wherein the cover body is made of brass is produced, the transmitting and receiving section with the sound-permeable rubber seal, a sound-permeable rubber 1 is a special material, it is capable of transmitting a larger part of the acoustic energy in order to ensure the loss of the ultrasonic wave is minimized [5]. The anti-resonant frequency of the frequency of the transmitting end and the receiving end of the probe are 2MHz ± 30kHz will be sending and receiving transducer is fixed at both ends of a metal tube, so that to ensure the ultrasonic wave propagation every sound path are fixed, then perforated metal tube around, so that oil can be filled, the measurement results of the experiment proved that this structure is ideal. Probe portion of the structure, such as: the completion of the test data analysis and conclusions instrument soft, hardware design, in order to verify the effect of the instrument in the detection of the actual oil density, the large number of finished oil experiments, the instrument using a data processing method is Newton interpolation method, which can eliminate the systematic errors. Are listed in the portion of the data in the test, wherein the true density is obtained by standard density measurement in accordance with the density of oil and liquid petroleum products assay (densimeter method GB/T1884-1992) oil real density.

According to the above data, it can be seen that the propagation time of ultrasonic waves increases with decreasing oil density, which is consistent with the theoretical conclusion, and measurement errors are less than 0.0005g/cm3 to achieve the precision requirements . The device density than traditional oil detection method is more suitable for the dynamic measurement of the density of the oil, and fully meet the needs of online testing.


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