Research on Target Deviation Measurement of Projectile Based on Shadow Imaging Method in Laser Screen Velocity Measuring System

In the laser screen velocity measuring (LSVM) system, there is a deviation in the consistency of the optoelectronic response between the start light screen and the stop light screen. When the projectile passes through the light screen, the projectile’s over-target position, at which the timing pulse of the LSVM system is triggered, deviates from the actual position of the light screen (i.e., the target deviation). Therefore, it brings errors to the measurement of the projectile’s velocity, which has become a bottleneck, affecting the construction of a higher precision optoelectronic velocity measuring system. To solve this problem, this paper proposes a method based on high-speed shadow imaging to measure the projectile’s target deviation, ΔS, when the LSVM system triggers the timing pulse. The infrared pulse laser is collimated by the combination of the aspherical lens to form a parallel laser source that is used as the light source of the system. When the projectile passes through the light screen, the projectile’s over-target signal is processed by the specially designed trigger circuit. It uses the rising and falling edges of this signal to trigger the camera and pulsed laser source, respectively, to ensure that the projectile’s over-target image is adequately exposed. By capturing the images of the light screen of the LSVM system and the over-target projectile separately, this method of image edge detection was used to calculate the target deviation, and this value was used to correct the target distance of the LSVM to improve the accuracy of the measurement of the projectile’s velocity.

Implementation of Double-Timing Pulse Interpolation Applied to Compact Piston Provers

This work presents an electronic circuit for double-timing pulse interpolation applied to compact piston provers (also referred as small volume provers). Compact provers are usually employed to prove meters with pulsed outputs. API and ISO standards [1,2] recommend a minimum of 10.000 pulses per run to obtain a resolution better than ± 0.01%. Since the volume of fluid displaced by a compact prover is relatively small, the number of pulses produced during a proving run is often considerably less than 10.000 pulses. Pulse interpolation techniques are commonly used to increase resolution and to diminish uncertainty during a proving run by estimating the fractional part of meter pulses within the time interval of the calibration. In this way, pulse interpolation techniques are essential to obtain accurate flow measurements and to allow the calibration of meters with compact provers. Our implementation uses a compact piston prover with an internal volume of 12 L and maximum flow capacity of 180 L/min. In order to implement the double-timing pulse interpolation method, we have used a Pentium D, 2.80 GHz installed with a 16-bit counter/timer board. Data acquisition and control software were written using VB .Net. An electronic circuitry was built to activate/deactivate counters gates, and to collect pulses. Some requirements and limitations of pulse interpolation techniques such as circuitry testing and pulse stability are also discussed in this work.