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    download analisa wallpapers

    Name: download analisa wallpapers
    Category: Download
    Published: maihydurchli1989
    Language: English

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

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    Before understanding how the sensor works, it is worth looking at some of the terminology used as this is extremely useful to know when identifying a sensor. Flat film sensing elements are extremely versatile devices but do suffer some drawbacks. They can operate over a wide temperature range, generally -70 to +500°C. They are only available in the lower tolerance bands of Class B and Class A. Some are available as 1/3 DIN. As the accuracy increases there are limits placed on the temperature range of the detector. The last disadvantage only applies in applications where the temperature is cycling between two extremes. Because the Platinum is fused to the ceramic substrate and there are other layers in the construction of the element, the conducting grid is not able to expand and contract freely, it is constrained by the other layers. This can cause stresses within the wire which affect the resistance and therefore the accuracy. PT100 Working Principle. With both types of sensing element, the construction of the finished temperature probe generally follows very similar methods and techniques. In general, a Pt100 should be housed in a metal housing or sheath to provide protection from the outside environment. The housing is usually 316 stainless steel as this is an excellent general-purpose material for the majority of applications. It is however possible to use alternatives such as 310 stainless steel or Inconel if necessary. In some cases, it is permissible to use an exposed or ventilated element for the measurement of dry gases. The exposed sensor should never be exposed to water or conducting liquids. The sensor type, Pt100, indicates two important pieces of information about the sensor. The first part, Pt, is the chemical symbol for Platinum and this shows that the sensor is Platinum-based. The second part, 100, relates to the resistance of the device at 0°C. In this case 100Ω. There are a number of variations on this theme. There are other materials that can be used such as Nickel (Ni) and Copper (Cu) and different resistance values such as 50Ω, 500Ω and 1000Ω. This gives the possibility of sensors being identified as follows:- Why use Platinum? The Pt100 variant is however the most commonly used. Sensors using Platinum are also by far the most common group and are often referred to as Platinum Resistance Thermometers or PRT’s. In practical terms, the sensing device is a very small measuring element which is based on one of two technologies. For higher volume, lower cost and general-purpose industrial applications it is normal to use a Flat Film Sensing Element. This type of element has a ceramic substrate onto which a very fine Platinum grid is deposited. This grid is trimmed by laser to give the characteristics demanded by the standards. Each element is calibration checked and graded according to the tolerance band into which it falls. Flat film elements are manufactured in an automated system which gives high production rates and they are used in high volume automotive and white goods markets too. The construction of the element means it is highly robust despite being very small and can withstand higher levels of shock and vibration than other types. Surface mount devices are also now available using this sensing technology. PT100 Working Principle also known as RTD PT100 working principle – Although Platinum is a precious metal and therefore very expensive it gives the greatest linearity and stability of any other material. It also has the benefit of being extremely resistant to corrosion and chemical attack and is very stable at high temperatures. As well as being used in Platinum Resistance Thermometers, it is also used in some high-temperature thermocouples. The mass of Platinum used in manufacturing the sensing elements is extremely small so the cost is surprisingly low and only represents a small proportion of the total cost of the finished temperature probe. This set of characteristics is set down in the relevant European and International Standards. In the UK we comply with BS EN 60751:2008 and this standard stipulates the resistance value, resistance change characteristics, tolerances and colour code for extension cables. All Pt100 temperature sensors manufactured by Process Parameters comply with this specification and are completely interchangeable with sensors from other manufacturers. PT100 Sensor Working Principle. PT100 sensor working principle – A Pt100 is a sensor used to measure temperature. It is one type of sensor which falls into a group called Resistance Temperature Detectors or RTD’s. Industrial Use of Pt100’s. RTD PT100 Working Principle Continued. Cu100, Ni120, Pt1000. The sensing element itself is joined to an extension wire or cable in order to provide the resistance output to a point where it is measurable. Process Parameters always weld extension wires to the sensing elements as this provides a higher temperature join that soldering and gives the lowest possible resistance between the cable and detector. The sensor is then potted into the housing using various materials depending on the temperature range required and the other environmental conditions. We can provide constructions for very low temperatures down to -200°C all the way up to 650°C. In general, sensors are either terminated in a cable, a terminal housing or a connector. Process Parameters offers all these options. As mentioned previously the Pt100 temperature sensor falls into a group of sensors called Resistance Temperature Detectors. The key word is “Resistance” because a Pt100 measures temperature by using a resistance change to denote the temperature value. For a Pt100, the resistance at 0°C is 100Ω and at 100°C, it is 138.5Ω. Therefore, the resistance change for each degree Celsius change is 0.385Ω. The second type of sensing device is the wire-wound sensing element. This type of detector is manufactured in far smaller volumes by hand. Despite their higher cost, they provide the highest possible levels of reliability, particularly with respect to long term drift. The sensing element is based on a multi-bore ceramic insulator. A hand made helical coil of Platinum wire is placed in one or more of the bores and carefully trimmed to provide the correct characteristics. The benefit of this design is that the Platinum wire is simply supported. This means it can expand and contract with temperature changes which avoids a build-up of stresses within the wire, therefore, reducing the potential for long term drift. Because the wire is simply supported this type of sensing element is not suitable for applications where there is a high shock of vibration loads on the sensor. The main advantage of a wire-wound sensing element is the ability to work at a higher temperature as standard, generally up to 650°C and they are also available with tolerances to the highest level. They are also the only option for sensors required to operate to cryogenic temperatures of -200°C.

     

     

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