Kalibrierung und Justierung von Feuchtemessgeräten ? Vor- und Nachteileverschiedener Methoden
Devices for the measurement of the relative dampness can be calibrated and/or adjusted in different way. The ideal case would be to examine and certify all devices in an accredited laboratory according to highest standards. In the reality however possibilities must be found, in order to bring time factors, costs, technical requirements, specialized knowledge and special requirements of the users in agreement. As assistance with the selection of approaches and calibration procedures some the most frequently used methods as well as their pro and cons are described here. First however four terms should be clarified, which emerge with all calibration procedures. Calibration � procedure, with which the values determined with a measuring instrument are compared with those a reference or Normals. Adjustment � procedure, with which the announcement of a measuring instrument, thus the measured/indicated value (the actual value so called) to the correct value, which desired value so called is corrected, as well as possible. Calibration interval � time difference between two sequential calibrations by measuring instrument process status pool of broadcasting corporations � a measuring instrument, which was calibrated assistance of a secondary or Prim�rnormals, in order for the calibration of other measuring instruments to be then used. The word � calibration � becomes frequently, but not generally, when comparison misinterprets inclusive adjustment. In order to prevent misunderstandings, you should not assume a calibration also generally includes an adjustment with. Often manufacturers are asked by customers, which calibration intervals would recommend them. That is a reasonable beginning, but in practice the efficiency of a measuring instrument can diminish depending upon way of application with the time. Therefore it lies with the user to specify the calibration intervals. Metrologen try to solve the problem, by calibrating the measuring instrument regular to adjust (without it) and the data log, until the measured value drift exceeds the permissible tolerances. The calibration interval is the time difference between the calibration at the time tn and the following calibration at the time tn+1. between these two times is the equipment in the calibrated operational condition. This interval is supervised calibrations by additional, less frequent, until an acceptable achievement process is recognizable. Process status pool of broadcasting corporations can be each measuring instrument, which is used for the calibration of another measuring instrument. Accuracy and repeatability are not crucial thereby for this process status pool of broadcasting corporations. Performance data of the work standard should be suitable only for the intended use. It is important that this process status pool of broadcasting corporations in regular intervals assistance of a Sekund�roder Prim�rnormals calibrated and the operational behaviour is carefully supervised and documented. Temperature � a more substantially factor-relative dampness is extremely temperature-dependent. In order to obtain the optimum calibration results, all mechanisms, which are used for the calibration, should have a balanced temperature. Have that means that the calibration environment exhibits a stable temperature, and the process status pool of broadcasting corporations as well as the equipment the same temperature which can be calibrated. If these conditions cannot be manufactured, it will come by the temperature gradient to errors during the calibration. In practice means: portable work standards must be able themselves to adapt to the ambient temperature locally. That applies above all then, if a normal, which was stored at ambient temperature, is used in a process or an environment, with those higher or lower temperatures than the ambient temperature� arise. In situ a point calibration with this method process status pool of broadcasting corporations is used, in order to calibrate a stationary operating measuring instrument, without setting this out of operation. Thus e.g. a technician assistance of a portable measuring instrument can do one at the wall installed sensors to examine. The crucial advantage thereby is that the procedure can be accomplished fast and simply. There are no down-times for the operating measuring instrument, and there is not necessary additional workers for the disassembly. A disadvantage thereby is however the absence of a second calibration point, in order to prove the correct dynamic holding back thing of measuring instrument. If the environment hiring are subjected to only small fluctuations, there can be sufficient, anzuhauchen that sensors easily, in order to then observe its reaction as well as re-establishment. If the site conditions should vary however more strongly, a multipoint calibration is to be preferred. Multipoint calibration in point of operating two or three point calibrations can be accomplished locally assistance of dampness generators, if the environment exhibits a stable temperature. Appreciative humidity is producible with a multiplicity of mechanisms. All wise however certain restrictions or requirements up. A satisfied salt bath is easy e.g. an economical solution and in addition to transport. However sufficiently time must be taken into account, in order to reduce the dampness fluctuations due to temperature differences to a minimum. Since salt baths are not restorable regarded as, returnability must be ensured e.g. by the use of a suitable work standard in the salt bath as well as the test specimen. The advantage of a multipoint calibration locally is in the fact that thereby the correct function of an operating measuring instrument can be ensured over the certain area of application. Unfortunately these calibrations are more difficult to accomplish than simple in situ calibrations of point of a. Technicians need for it a more extensive equipment, and the operating measuring instrument must work off-lines. The procedure can take well one hour, sometimes also longer. In addition the conditions are often not optimal locally, so that it is difficult to obtain a high measure of accuracy. Calibration in in-house laboratory-unites enterprises possesses own, metrologische laboratories with the pertinent capacities for measuring instruments and calibrations. One finds laboratories of this kind particularly in enterprises, which must hold a large number of measuring instruments and/or measurements within critical ranges would drive through. Calibrations in laboratories in-house offer many advantages. The possibilities of the laboratory can be adapted to the requirements of the enterprise. In some cases thereby completely the responsibility for the efficiency of the measuring instruments is removed from the users. Metrologen can determine calibration intervals, and trained technicians would drive through their work on highest level in a controlled surrounding field. A fast turn-around time makes and individual customer hour possible lasts, sometimes also longer. In addition the conditions are often not optimal locally, so that it is difficult to obtain a high measure of accuracy. Calibration in in-house laboratory-unites enterprises possesses own, metrologische laboratories with the pertinent capacities for measuring instruments and calibrations. One finds laboratories of this kind particularly in enterprises, which must hold a large number of measuring instruments and/or measurements within critical ranges would drive through. Calibrations in laboratories in-house offer many advantages. The possibilities of the laboratory can be adapted to the requirements of the enterprise. In some cases thereby completely the responsibility for the efficiency of the measuring instruments is removed from the users. Metrologen can determine calibration intervals, and trained technicians would drive through their work on highest level in a controlled surrounding field. Makes possible a fast turn-around time and an individual customer service in case of special requirements. In larger enterprises these advantages can be limited however by the fact that the Kalibriereinrichtung is not in the proximity of the operating measuring instruments. Commercial KalibrierlaboratorienEs gives profit-oriented mechanisms, which offer calibration services. The measuring instruments are in most cases taken out of operation and sent for calibration to the laboratory. Some commercial laboratories place coworkers to removement and replacement of the measuring instruments to the order. By some also a suburban calibration in mobile laboratories becomes offered. Commercial laboratories are particularly meaningful for the enterprises, which must calibrate a so small number of devices that an investment is not justified in Kalibratoren. The specialized authority of the laboratories is different. Some offer qualitatively high-quality calibration services, which are only exceeded by the national standardization places, like for example to the NIST. Other commercial offerers specialized for example in dampness conditions, which are to be manufactured only with difficulty, for example extremely high or low moistening in extreme temperature ranges. With the search for a suitable calibration laboratory it is to be made certain recommendable that it concerns an accredited laboratory, i.e. that the laboratory was examined and certified by an independent institution. As result of the certification procedure a clearly defined field of application for the laboratory is fixed. This field of application defines all measured variables, measuring range and uncertainties, which the laboratory exhibits. In Europe certification bodies in all member states exist for the accreditation and monitoring of calibration laboratories; complete lists of the accredited laboratories are published by these places.
This text was translated automatically.
