Time Measurement Method Research Articles

Method for effective dead time measurement in counting systems

The counting losses introduced by the dead time of a counting system are a limiting factor in counting measurements. The purpose of this work is to report an efficient method for the measurement of the effective dead time of a counting system and to characterize its dead time behavior, providing a way to investigate each experimental situation. The method, which we designate as Delayed and Mixed Pulses method, is based on the artificial piling-up of detector pulses with electronic pulses delayed by a specific time interval. It is applicable to the measurement of the effective dead time of a counting system, including both pile-up effects and the dead time characteristics of the elements of the counting chain. With counting systems relying on gaseous radiation detectors, we achieved a standard uncertainty of about 5–10% in the dead times measured.

A robust and accurate algorithm for time measurements of periodic signals based on correlation techniques

Algorithms incorporated in the oscilloscopes allow automatic measurement of periodic waveforms. These algorithms are often based on IEC Standards. They are not only useful for built-in oscilloscope measurements, but also as stand-alone algorithms implemented, for example, on a computer. The conventional algorithms used for time measurement of periodic signals (e.g., period, positive and negative duty cycles and pulse widths) are based on crossings of a reference level. The crossings method for time measurement fails when there are spurious crossings around the reference level. We have developed a robust and accurate algorithm for time measurement of period, duty cycle, and pulse width, based on correlation techniques. The algorithm for determining the period is generic to any periodic waveform with at least one period. The algorithm for duty cycles and pulse widths is only valid for pulse-shaped waveforms. Using example waveforms, our algorithm is shown to produce more robust and accurate time measurements than the built-in algorithm used in a commercial oscilloscope. With modern-day computing power, our algorithm takes between 10 and 20 ms to perform measurements for a waveform of 1000 8-bit data-points on a Pentium III laptop.

A new method of carrier trapping time measurement

A new method of measuring carrier trapping time by a simple analysis of the current pulse shape is proposed and demonstrated for irradiated silicon detectors. This method which we call Exponentiated Charge Crossing (ECC) requires no knowledge of either the electric field profile in the detector or of the relation between the carrier drift velocity and the electric field. It is general enough to be valid not only for solid-state particle detectors but also for other devices such as some gaseous and liquid detectors. The results obtained by the proposed method are consistent with those obtained by an earlier method.

A simple method for measuring shear stress on rough boundaries

This technical note presents a simple method for the real time measurement of bed shear stress with a LabView Program for turbulent flow over uniformly rough boundaries, based on the classical logarithmic velocity distribution equation. The method is based on a step-wise linearization of the additive coefficient in the classical logarithmic velocity distribution equation.

Reconsideration of Dead Time Measurement by Wavelet from Phase Property of Frequency Response

This paper provides another view of the dead time measurement method, which we have already proposed. The method measures a dead time of a linear system from a wavelet transform of a cross correlation function between an input and an output. On the other hand, we notice that the wavelet transform of the cross correlation function has a close relation to the frequency response of the system. The objective of this paper is to derive this relation and present another view of the dead time measurement method. In order to achieve the objective, we consider a relation between the wavelet transform of the cross correlation function and the corresponding cross spectrum.

Travel Time Measurement Using Ultrasonic Vehicle-Identification Equipment

This paper describes a new method of the travel time measurement based on the vehicle height data from the ultrasonic vehicle-identification equipment which has been developed using the pulse-type ultrasonic vehicle detector. The travel time is obtained by the difference of each passage time when the pattern matching of the vehicle data at upstream and downstream points is executed. However, there are following two problems which do the pattern matching using vehicle height data difficult. (1) The vehicle height data fluctuates by road surface condition and driving situation etc. (2) There are many resembled shape vehicles in a set of measurement object. Then, we analyze the vehicle height data, and construct the algorithm considering the possibility distribution on parameters for the vehicle pattern matching. Finally, we show the effectiveness of the proposed method by experiment of the travel time measurement.

Detection of scintillation light in coincidence with ionizing tracks in a liquid argon time projection chamber

A system to detect light from liquid argon scintillation has been implemented in a small, ICARUS-like, liquid argon time projection chamber. The system, which uses a VUV-sensitive photomultiplier to collect the light, has recorded many ionizing tracks from cosmic-rays in coincidence with scintillation signals. Our measurements demonstrate that scintillation light detection can provide an effective method for absolute time measurement of events and eventually a useful trigger signal. (C) 1999 Elsevier Science B.V. All rights reserved.

The drift mobility and decay of photocurrent in doped amorphous diamond-like carbon films

Abstract This paper presents results of the measurements of dark current and photocurrent, mobility, and decay time of photocurrent of doped and undoped a:DLC films as a function of temperature. The a:DLC films were grown by a r.f. glow discharge technique using methane gas, CH4, as a source of carbon. Several films were doped employing iodine (I2) as doping gas. a:DLC films have shown the photoconductivity effect for a wide range of temperatures. A maximum photosensitivity ratio σph/σd (σph is the conductivity under irradiation and σd the dark conductivity) of 1100 was achieved for iodine doped a:DLC films (I-DLC) at T = 140 K. The drift mobility was determined by the steady-state photocurrent and photocurrent decay time measurement method as a function of temperature. The highest drift mobility, 4.2 × 10−7 cm2 V−1 s−1, was obtained for I2 doped films at room temperature. The drift mobility at high temperature is thermally activated with an energy of 0.16 eV for doped and 0.13 eV for undoped films. In this case, it was assumed that the temperature activated behavior results from the interaction of free carriers with traps below the extended state transport levels. However, for low temperatures it was observed that the drift mobility is weakly dependent on temperature. This is due to the hopping transport mechanism.

Numerical method for transit time measurement in ultrasonic sensor applications

In this paper, the implementation of a novel algorithm for the measurement of the transit time is reported. It has been applied to implement a smart, ultrasonic sensor for the fluid level measurement on a tank by processing the detected signal. A prototype of an on-line operating device, assembled to demonstrate the performance of the algorithm, is also described. Simulation tests have been carried out to investigate the algorithm performance, and we report on the results obtained. In addition, the results obtained during the field testing and application of the developed sensor are reported.

Ultrasonic pulse-phase method applied in fluid flow measurements

A novel pulse phase method for ultrasonic flow measurement in pipes under pressure is presented. It belongs to a group of direct time measurement methods. The difference in propagation (transit) time between two ultrasonic beams transmitted in upstream and downstream directions across the fluid flow is measured. With a goal to achieve an accuracy better than 1% each of the transit time intervals is decomposed into two intervals. The first interval, called ‘coarse’, points to an integer number of the ultrasonic signal periods during propagation time, and the second one, called ‘fine’, points to the rest of its periods. Fluid flow velocity and volume quantity are determined through involving the calibration function. The main metrological characteristics of the realised fluid flowmeter are determined using available working etalons. Experiments have shown that the total error of the flowmeter described herein is within the specified accuracy of 1%.

Properties of bit-rate-independent pulse timing measurement technique using optical heterodyne cross correlation

A novel technique for detection of the time delay between optical input signal data and a clock, suitable for applications to phase-locked loops, is investigated. This pulse timing measurement scheme, which is based on heterodyne cross correlation employing passive optical mixing, does not rely on any characteristic time associated with an optical nonlinearity, and is virtually independent of the bit rate. Experimental results on self-heterodyne correlation of mode-locked laser pulses as well as detailed theoretical analysis indicate that the timing measurement method investigated is characterized by high sensitivity.

A Method for Response Time Measurement of Electrosensitive Protective Devices.

A great step toward the improvement of safety at work was made when electrosensitive protective devices (ESPDs) were applied to the protection of press and robot-assisted manufacturing system operators. The way the device is mounted is crucial. The parameters of ESPD mounting that ensure safe distance from the controlled dangerous zone are response time, sensitivity, and the dimensions of the detection zone. The proposed experimental procedure of response time measurement is realized in two steps, with a test piece penetrating the detection zone twice. In the first step, low-speed penetration (at a speed vm) enables the detection zone border to be localized. In the second step of measurement, the probe is injected at a high speed Vd. The actuator rod position is measured and when it is equal to the value L registered by the earlier measurements, counting time begins as well as the monitoring of the state of the equipment under test (EUT) output relays. After the state changes, time tp is registered. The experimental procedure is realized on a special experimental stand. Because the stand has been constructed for certification purposes, the design satisfies the requirements imposed by Polski Komitet Normalizacyjny (PKN, 1995). The experimental results prove the measurement error to be smaller than ± 0.6 ms.

軸対称アークプラズマの光学的直径とピーク分光強度の新しい実時間測定法

This paper describes a simple method for the real time measurement of the optical diameter and the spa-tial peak spectral intensity of the axially symmetric arc plasmas. The method only uses the integrated radia-tion intensities across the plasma column and along the central line of plasma cross section, which are meas-ured by a 2-channel programmable digital storage oscilloscope to obtain continuously the temporal variation of the optical diameter and the spatial peak spectral intensity of the plasmas.This method was applied to a Hg arc plasma and it was found out that the optical diameter had no tem-poral variation even if the discharge current was varied.

Measurements and analyses of multipath propagation structure for small‐cell digital mobile radio in hilly areas

AbstractFor research on characterization and reduction of the bit error rate in high‐speed digital mobile communication, the understanding of the multipath propagation structure is indispensable. In this research, a measurement system is developed in which the two sets of directive antennas and the delay time measurement method by TV video signals with a sharp pulse inserted are combined.The multipath propagation structure is measured in detail in hilly small‐cell model areas. In addition to conspicuous reflections from the buildings and hills around the measurement course, the reflected waves from far away buildings and multiple (several times) reflected waves are observed. The power‐delay profiles and the nature of the delay spread of the multipath waves are analyzed so that the effect of the delayed multipath waves on the bit error rate in the digital transmission is found.

Photorefractive response time measurement in GaAs crystals by phase modulation in two-wave mixing

We describe a new method for photorefractive response time measurement in fast photorefractive crystals based on continuous phase modulation in two-wave mixing. We report experimental results for undoped semi-insulating GaAs that are in good agreement with theory. Values obtained for the response time and photoelectron generation quantum efficiency are consistent with previously published data.

Decay time measurement of fluorescent fibers with photon counting

In order to characterize fluorescent light, we present a decay time measurement method based on the use of a commercial photon counting module. This module, adapted for all fiber measurements, is well adapted for the developing field of optodes for chemical and biochemical sensing. Moreover, it improves the detection sensitivity to the femtowatt and picowatt range. It is thus possible to excite the fluorescence with very low power pump pulses, down to a few nanowatts, and to measure the temporal distribution of the fluorescent signal. As sources we can use LEDs, or white lamps plus a monochromator, avoiding unwanted phenomena such as saturation, amplified spontaneous emission (ASE), and excited state absorption (ESA). We obtain a measurement accuracy of 0.1% in a couple of minutes.

Speckle correlation method for the real time measurement of motion paths using liquid crystal television

A speckle correlation method is described in which a liquid crystal television (LCTV) is used as a spatial filter to measure the paths of the lateral motion of rough objects. Two kinds of speckle patterns are generated simultaneously, consisting of speckles elongated in orthogonal directions to each other. The two-dimensional motion vector of the object can be measured in real time by correlating these patterns with static speckle patterns that are displayed on the LCTV as the references. Because these reference patterns can be renewed in real time, there is no limit for a measurable range of the present method. However, the spatial resolution and contrast of the LCTV limit the sensitivity and accuracy of the method.

食品テクスチャーの違いがえん下までのそしゃく時間に与える影響

This study was made to investigate the effect of food characteristics on masticatory time until swallowing. Using a kinesiograph (Model K6, Myo-tronics Co.), the three-dimensional jaw movement was recorded from the beginning of mastication to the swallowing in 30 (15 male, 15 female) normal subjects and 15 (8 male, 7 female) patients with craniomandibular disorders (CMD). Cheese, kamaboko, takuan, senbei, surume and gumi were used as test food. For each food, the hardness, cohesiveness, gumminess, fracturability, stickiness and adhesiveness was quantified by a texturometer (Zenken Co.). Multiple regression analysis was applied for investigating the relationship between food texture and masticatory time. And using sensitivity and specificity, a screening test was also made for evaluating the accuracy of the diagnostic method for the masticatory time measurements of each test food.The results obtained were as follows:1. Cheese, kamaboko, takuan, senbei, surume and gumi showed quantitatively different types of food texture. In both normal subjects and CMD patients, the longest masticatory time was surume, the shortest was cheese.2. From multiple regression analysis, in both normal subjects and CMD patients, gumminess and volume related to the masticatory time.3. From results of high sensitivity and specificity, it is clear that 40 sec for large size of surume as the criteria is important for making a clinical examination and diagnosis of CMD patients.

Evaluation of PACS-induced organizational change

Filmless digital imaging with a PACS will affect health care institutions by changing the handling of clinically relevant information, altering needed staffing levels, and possibly affecting both the quality and cost of care. Economic evaluation of PACS compares the costs and/or benefits of PACS with those of all other relevant alternatives. Other evaluations may focus on narrower research questions. This paper discusses methodological considerations in economic evaluation, methods of time measurement, and the methods and results of several applied assessments of PACS effects on the medical imaging department or the hospital.

An address access time measurement method for high‐speed mos static rams

AbstractWith the advance of a high‐speed MOS static RAM (SRAM), it is considered a problem to measure the access time of SRAM more accurately. In the measurement of the address access time, it is assumed that a large number of address signals are all simultaneously forced on SRAM. In the actual measurement of SRAM, however, it is difficult to determine the forcing time of the address signals at the input of SRAM. Consequently, the foregoing condition is difficult.This paper considers the measurement of the address access time of the high‐speed SRAM and proposes a method whereby the forcing time of the address signal can easily be measured and corrected on the memory tester. In the method, the GND bounce generated in SRAM itself in response to the given address signal is measured in the reference SRAM. Then the variation of the address signal forcing time is evaluated quantitatively and corrected. The proposed method is applied to a commercial memory tester to measure the address access time in 64‐kbit CMOS SRAM with the maximum access time of 15 ns. As a result, the variation of the address signal forcing time is kept within ±100 ps, and the measurement error of the SRAM address access time with different testers is within 1 ns, which is satisfactory.