Druckmessung im 10–3 mbar Bereich mit Wärmeleitungs‐ und Membran‐Vakuummeter

Pressure measurement in the mTorr range by thermal conductivity and diaphragm gauges For the reliable and simple pressure measurement in the mTorr range, the thermal conductivity and the capacitance diaphragm gauge can be used. Gauges of both types were employed for measuring the pressure in the bell jar of a piston gauge. The measuring characteristics of the gauges were checked regularly by calibrations and proved to be stable. According to the calibration data, the thermal conductivity gauge apparently is advantageous due to its better zero stability. In the practical use, however, substantial differences between the pressure readings of both gauges were observed. Therefore, in the present work the characteristics of both gauges have been investigated for the case of their actual usage, in which the pressure of an unknown gas has to be measured within a short time period. The investigations reveal, that the thermal conductivity gauge suffers from its slow response at small pressures and its dependency on gas species. In the present application, the capacitance diaphragm gauge proves as the far superior gauge.     

Modifiziertes Bayard‐Alpert‐ Ionisationsmanometer für Druckmessungen von 10‐9 ... 10+1 mbar

Generally, the requirements for the design and the operating parameters of hot filament ionisation gauges for high and low pressure measurement are incompatible. Nevertheless it is possible to construct an ionisation gauge with a wide measuring range. For that purpose the electrode configuration and its operating parameters of a suitable gauge have to be optimised in this way that the contrary requirements are met with minor restrictions. With the help of computer simulations and experimental investigations a vacuum gauge was developed which combines the main features of both different types of ionisation gauges in one gauge construction. According to our ideas a gauge geometry similar to the ordinary Bayard Alpert gauge enables to measure the pressure in an extended operation range by using not only the pressure dependence of the formation of ions but additional the pressure dependence of the ion drift velocity in an electric field in the upper pressure range too. The upper pressure limit of this ionisation gauge can be shifted up to the rough vacuum range without changing the lower pressure limit of 10^‐9 mbar as usual for Bayard‐Alpert gauges. Thus, the operation range of this modified gauge cover nearly ten decades of pressure.     

An algorithm for fast regulation of dynamically generated pressures in the range 1 Pa-7 kPa

An innovative regulation algorithm that allows to stabilise quickly the pressure in the range 1 Pa-7 kPa in a leaky chamber using a commercially available pressure regulator designed for atmospheric pressure range has been developed. The algorithm has been implemented on a nonrotating digital piston gauge allowing automatic calibration of pressure sensors. This algorithm could be used helpfully to generate starting pressures for dynamic expansion systems.     

Gepulstes Heißdraht‐Vakuummeter mit Pirani‐Sensor. Pulsed hot filament vacuum gauge with Pirani sensor

The hot filament gauge according to Pirani is usually operated in the stationary mode in which the applied electrical heating power equals the total heat losses. The heat loss by the thermal conductivity of the gas increases with increasing pressure which allows to derive the measuring signal for the pressure. However, at pressures above some 100 mbar the thermal conductivity starts to saturate which results in a strong decrease of the measuring accuracy of the hot wire gauge. A few years ago, a proposal was published to make use of the heat capacity of the gas which is proportional to pressure. Subject of the present paper is a decisive investigation of the dynamical behaviour of the Pirani sensor. For this purpose, both the heating and cooling processes of the wire were measured. As follows from the experimental data and theoretical estimations, a considerable amount of energy is stored in the gas at atmospheric pressure, i.e. much more than in the wire, but this energy content has only a small effect on heating and cooling rates. Reasons for this behaviour are the strong heat losses by the thermal conductivity of the gas, the rather weak thermal coupling between the wire and surrounding as well as the smallness of the average temperature increase of the gas. Furthermore, an intermittent operation of the Pirani sensor was tested in which the voltage applied to the wire gradually increases. Advantages of this operation mode are a significant improvement of the measuring characteristics above 100 mbar and a substantial reduction of the power consumption.     

A Solution‐Processable,Omnidirectionally Stretchable,and High‐Pressure‐Sensitive Piezoresistive Device

The development of omnidirectionally stretchable pressure sensors with high performance without stretching‐induced interference has been hampered by many challenges. Herein, an omnidirectionally stretchable piezoresistive pressure‐sensing device is demonstrated by combining an omniaxially stretchable substrate with a 3D micropattern array and solution‐printing of electrode and piezoresistive materials. A unique substrate structural design and materials mean that devices that are highly sensitive are rendered, with a stable out‐of‐plane pressure response to both static (sensitivity of 0.5 kPa^?1 and limit of detection of 28 Pa) and dynamic pressures and the minimized in‐plane stretching responsiveness (a small strain gauge factor of 0.17), achieved through efficient strain absorption of the electrode and sensing materials. The device can detect human‐body tremors, as well as measure the relative elastic properties of human skin. The omnidirectionally stretchable pressure sensor with a high pressure sensitivity and minimal stretch‐responsiveness yields great potential to skin‐attachable wearable electronics, human–machine interfaces, and soft robotics applications.     

大量程位移传感器用于三等量块检定时不确定度分析

对于三等或三等以下量块的检定，受位移传感器测量范围的精度的限制，一直采用比较测量方法。近年来，随着高精度大量程位移传感器的出现，使得采用直接测量方法检定量块成为可能。本文介绍了用大量程位移传感器直接测量量块的方法，并对其不确定度进行了详细分析。     

The Micro Pirani™: A solid-state vacuum gauge with wide range

For measuring pressures in the range 1 × 10^?2 to 100 mbar, thermal conductivity gauges are commonly used. The widespread Pirani gauge with a thin wire suffers from problems with temperature drift, low accuracy, requirement for adjustment, large measuring volume, filament contamination, and sensitivity to mounting position. Recently, Wenzel Electronics has introduced the Micro Pirani?, which is based on a newly developed solid-state sensor element and which eliminates or significantly reduces the problems. A temperature compensation improves the stability and extends the useful range of operation to the high vacuum range at 1 × 10^?5 mbar. The geometry of the basic sensor element, close to “infinite slab geometry”, facilitates the introduction of a fairly accurate mathematical model of the sensor. The sensor is insensitive to mounting position since no convection can take place in the sensor due to its small dimensions. Furthermore, the internal volume (“dead volume”) has been significantly reduced as compared to traditional Pirani sensors. The conversion from transmitter output voltage to pressure is achieved by a simple and fast algorithm. The selection of a particular gas species is simple, since the algorithm contains only 3 gas-dependent constants. An excellent reproducibility in production eliminates the need for an individual calibration of individual sensors in most applications.     

指针式压力表自动计量校准系统

目前,指针式压力表常采用影像法进行计量校准,但在计量过程中存在压力表指针难分割、背景难分离和识别准确率低等问题,为解决上述问题,结合不同规格压力表表盘的外观尺寸,对压力表自动计量校准系统进行研究。首先,根据工业相机视野范围内压力表表盘外形尺寸,自动判断相机与压力表之间最佳工作距离;其次,利用图像边缘梯度值评价图像清晰度,自动完成相机对焦;最后,采用极坐标转换方法实现刻度线定位、指针提取、实时读数等功能。测试结果表明,该系统适用于外壳直径为40,60,100,150,200,250 mm的指针式压力表计量校准。     

Nanoparticle‐Structured Highly Sensitive and Anisotropic Gauge Sensors

The ability to tune gauge factors in terms of magnitude and orientation is important for wearable and conformal electronics. Herein, a sensor device is described which is fabricated by assembling and printing molecularly linked thin films of gold nanoparticles on flexible microelectrodes with unusually high and anisotropic gauge factors. A sharp difference in gauge factors up to two to three orders of magnitude between bending perpendicular (B_⊥) and parallel (B_||) to the current flow directions is observed. The origin of the unusual high and anisotropic gauge factors is analyzed in terms of nanoparticle size, interparticle spacing, interparticle structure, and other parameters, and by considering the theoretical aspects of electron conduction mechanism and percolation pathway. A critical range of resistivity where a very small change in strain and the strain orientation is identified to impact the percolation pathway in a significant way, leading to the high and anisotropic gauge factors. The gauge anisotropy stems from molecular and nanoscale fine tuning of interparticle properties of molecularly linked nanoparticle assembly on flexible microelectrodes, which has important implication for the design of gauge sensors for highly sensitive detection of deformation in complex sensing environment or on complex curved surfaces such as wearable electronics and skin sensors.     

Adapting second‐order response surface designs to specific needs

Experimental design strategies most often involve an initial choice of a classic factorial or response surface design and adapt that design to meet restrictions or unique requirements of the system under study. One such experience is described here, in which the objective was to develop an efficient experimental design strategy that would facilitate building second‐order response models with excellent prediction capabilities. In development, careful consideration was paid to the desirable properties of response surface designs. Once developed, the proposed design was evaluated using Monte Carlo simulation to prove the concept, a pilot implementation of the design carried out to evaluate the accuracy of the response models, and a set of validation runs enacted to look for potential weaknesses in the approach. The purpose of the exercise was to develop a procedure to efficiently and effectively calibrate strain‐gauge balances to be used in wind tunnel testing. The current calibration testing procedure is based on a time‐intensive one‐factor‐at‐a‐time method. In this study, response surface methods were used to reduce the number of calibration runs required during the labor‐intensive heavy load calibration, to leverage the prediction capabilities of response surface designs, and to provide an estimate of uncertainty for the calibration models. Results of the three‐phased approach for design evaluation are presented. The new calibration process will require significantly fewer tests to achieve the same or improved levels of precision in balance calibration. Copyright © 2008 John Wiley & Sons, Ltd.     

激光量块干涉测量中传感器的应用和校准

本文介绍了双波长激光量块干涉仪中使用的温度、湿度和气压传感器,描述了其工作原理、设计方案、测量不确定度以及校准方法。这些传感器同样可用于其他高准确度长度测量的激光干涉系统中。     

Secondary Sensitivity Control of Silver‐Nanowire‐Based Resistive‐Type Strain Sensors by Geometric Modulation of the Elastomer Substrate

A secondary method for modulation of the sensitivity in silver nanowire (AgNW) resistive‐type strain sensors without the need to change the material or coating process in the sensory layer is demonstrated. Instead of using a planar elastomer (polydimethylsiloxane is used in this study) substrate, diverse relief structures are introduced to induce nonuniform and complex strain within the elastic substrate and thereby different distributions of the crack density of the AgNWs upon stretching, which plays an important role in the modulation of the gauge factor (GF). Analysis of the sensory layer and mechanical studies reveal that a lower height ratio and greater number of trenches enhance the sensor sensitivity, for example, reaching a GF of 926 at 9.6% in this study. The demonstration of wrist‐motion sensors using the technology illustrates the feasibility of using relief structures for various types of sensors and sensitivity ranges using an identical sensor layer.     

Verbessertes Kaltkathoden‐Ionisationsmanometer mit verlängerter Lebensdauer

Improved cold‐cathode gauge with extended life‐time If a cold‐cathode gauge is operated in a hydrocarbonous gas atmosphere at high vacuum pressures, its mean life‐time is substantially limited by a contamination of the electrodes and thus by a strong change of the gauge characteristic. Consequently, the pressure reading of the gauge becomes erroneous. This paper presents an improved cold‐cathode gauge of the inverted magnetron‐type, which was specially designed and developed for the long‐term operation at high pressures or/and in gas atmospheres with high contents of hydrocarbons. It was realized by a special electrode geometry using two separate and independent discharge chambers in one common gauge housing. Whereas the discharge zone positioned directly at the tube entrance works only as ion baffle, the second discharge zone located more interior is used only as gauge for pressure measurement. Compared with conventional cold‐cathode gauges the new gauge has a significantly extended useful life‐time. The prototype of the inverted double‐magnetron gauge and test results on its long‐term measuring behavior are presented.     

Maximum Gauge Pressure in Dangerous Goods Packagings Under Normal Conditions of Carriage – Comparison of Direct Measurement and Calculation

The objective of this work was to determine the maximum gauge pressure in the vapour phase above the liquid in different design types of dangerous goods packagings under normal conditions of carriage. The design types investigated were steel and plastic packagings with a volume of approximately 6 l. Two different methods were applied. In method 1, the pressure inside the packaging filled with a certain filling substance (dichloromethane) was directly measured under simulated conditions of carriage (degree of filling: 90%; filling temperature: 15°C; temperature during storage: 31°C). The maximum measured gauge pressures were between 89 mbar for a light plastic jerrican and 336 mbar for a steel drum. In method 2, the gauge pressure was calculated. The consideration of a rigid packaging combined with the assumption of a vapour pressure of zero during filling and sealing can serve as a worst case scenario. The calculated gauge pressure is approximately 1061 mbar. This procedure leads to the highest safety factor and does not require any experimental investigations. For a more realistic approximation of the gauge pressure of a non‐rigid packaging, a packaging‐specific function of relative expansion can be used, which is determined by a hydraulic pressure test. The calculated values ranged from 105 to 347 mbar. Method 2 provides conservative results. No hazardous filling substance is needed, and it allows a prediction of gauge pressure for other temperatures, substances and filling degrees. Therefore, this method could serve as alternative to UN Model Regulations 6.1.5.5.4 (a). Copyright © 2014 John Wiley & Sons, Ltd.     

A Remotely Controlled Calibrator for Chemical Pollutant Measuring-Units

The increasing diffusion of pollutant measuring units, which are installed over wide areas, along with the short calibration interval of several sensors for pollutant quantities, requires new calibration infrastructures to be developed. This paper describes an attempt to develop an innovative calibration system which is based on traveling standards and which does not require units to be removed from the measuring site during the calibration process. The calibration system is based on a traveling standard, which is composed of one or more cylinders that contain gas mixtures, a cell with standard sensors, and a control unit with networking capabilities, which allows the traveling standard to be remotely exercised. A prototype of the proposed system is described and the preliminary results reported.     

Stabilität von Hochvakuum-Meßröhren

Summary Hot filament and cold cathode ionization gauges are widely used in industry and research for pressure measurements in high and ultra high vacuum systems. Important applications are e.g. sputter and deposition systems. Since a long time it is accepted without a notice that the error of commonly used ionization gauges is typically 10% to 100%. The reason of this large error is the poor long term stability of the gauge sensitivity. If vacuum measurements must be precise and reproducible, long term stability of the vacuum gauges is the decisive issue. Only a stable gauge ensures correct control of processes. Also replacement of gauges should not produce differences in order to save time and money for new calibration. This paper reports experiments on the long term stability (several months) of widely used hot filament and cold cathode ionization gauges. Causes of timedependent instabilities are discussed. A new type of Bayard-Alpert gauge (STABIL-ION) is presented which offers a substantially improved long term stability compared to older design gauges.     

压力计量技术的近期进展

近十年来压力计量技术有了明显的进展。本文介绍了我国微压、中压和高压方面国家基准的改进和我国动态压力校准技术的进展情况。对于活塞式压力计的性能改进以及新型的强制平衡式活塞式压力计和数字式活塞式压力计的研制成功作了不少描述。还介绍了数字式压力控制器的迅速发展及其对压力计量工作的影响。     

现场真空校准装置的设计

基于客户提出的在工作现场对真空计进行校准的切实需求,研究并设计了现场真空校准装置。该装置主要由供气和进样模块、抽气模块、压力衰减模块、压力测量与校准模块、烘烤模块等五部分组成。考虑到现场环境对真空计的影响和校准装置易于携带、小型化的要求,设计中采用了模块化分体式结构,复合了静态比较法、动态比较法和压力衰减法等真空校准方法。可根据不同的校准需求,选配不同的模块和方法实现对真空计的校准。现场真空校准装置预计达到的技术指标是,校准范围为10-4～105Pa,合成标准不确定度小于7%。     

Digitaler Gasdosierer im Grobvakuumbereich

Digital gas dosing device for rough vacuum Vacuum gauges are calibrated by comparing the gauge under calibration with a reference gauge. Both gauges are mounted at a vacuum chamber. Different pressures are generated in sequence, and at each pressure the readings of both gauges are recorded. In the coarse vacuum range, the pressures are usually generated by successive injection of gas into the chamber via a manually operated dosing valve. This procedure requires some time and also fatigues the operator's hand. Therefore, a digital gas dosing device based on electromagnetic valves was developed, which allows a faster und more precise pressure generation than the analogue dosing valve and which is also friendly to the operators hand. Dosing device and its usage are described.     

Model and Experimental Characterization of the Dynamic Behavior of Low-Power Carbon Monoxide MOX Sensors Operated With Pulsed Temperature Profiles

Wireless sensor networks for home automation or environment monitoring require low-cost low-power sensors. Carbon monoxide (CO) metal-oxide (MOX) sensors could be suitable in terms of device cost, but they show some severe limits, such as the need to be heated, which means large power consumption and the need for complex and frequent calibration procedures, which increases the overall cost. This paper investigates the possibility to partially overcome these limits by a low-cost detection system based on a suitable commercial sensor (TGS 2442, Figaro, Inc.) and an ad hoc measurement technique exploiting specifically tailored temperature profiles. To this aim, the authors study the dynamic behavior of low-power CO MOX sensors operated with pulsed temperature profiles by means of two approaches: 1) sensor modeling and 2) experimental evaluation. To analyze how the sensor dynamic response changes as a function of the CO concentration, the authors individuate a temperature profile, which ensures satisfactory sensitivity to the target gas and very low power consumption. Moreover, some parameters describing the sensor response shape are selected, which prove to be significant in terms of both robustness to environmental conditions and calibration simplicity.