esz AG's field thermometry, temperature and environmental measuring technology is dedicated to temperature ranges from -80 °C to +1200 °C. Best practise in thermometer calibration (contact and immersion probes) is to rely on calibration baths or thermostat baths and dry block calibrators. The latter provide, along stabillity and reliability, almost maintenance-free robustness and short response time at wide temperature ranges, whether utilized at the stationary laboratory or on-site. Standard platinum resistance thermometers indicate marginal drift and result in measurement uncertainties below 15 mK. Utilizing a triple point cell, measurement uncertainities far below 15 mK are realized at water's triple point of 0,01 °C. Electrical base parameters for thermoelectric voltage and resistance are traceable to the electrical calibration laboratory, resulting in measurement uncertainties below 2 mK.
Calibrating the Temperature Scale
To record and calibrate temperature is of vital importance to many industrial procedures. Monitoring temperature is determined a key quality criteria for numerous products among multiple industries (e.g. food, steel, plastics industry). In addition monitoring and evaluating temperature has a direct impact on production control systems. Indicated, measured temperature is converted into electrical signals in order to be electronically processed.
Vast stability and reliability
Modern day calibration capabilities for temperature and thermometers are based upon themoelectric relation between voltage and resistance and realized applying thermocouples and resistance thermometers. Starting point is defining the temperature scale according to ITS-90, supporting fixed or triple points. The clearly identified cardinal point is water's triple point indicating a liquid, solid and gaseous state at exactly 0,01 °C. As opposed to freezing point temperature, the triple point is not affected by air pressure, oxygen level and as such repeatable at any time. At esz AG's thermometry laboratory the triple point is stabilized and kept alive for a day utilizing a triple point cell.
Infrared thermometer and Pyrometer Calibration
Calibration of noncontact infrared thermometer is performed applying a black plate thermal body combined with a pyrometer in order to transfer radiation temperature at spectral ranges from 8 µm to 14 µm and temperatures up to 550 °C. Pyrometry classifies measuring techniques characterizing surface temperatures. The latter is identified by energetic or spectral thermal radiation emitting from a surface. A pyrometer, also commonly refered to as a radiation or infrared thermometer, is used to perform the actual measurement. In contrast to pyrometry, thermography is best described as imaging pyrometry. Pyrometer enable "punctual" surface temperature characteristics. Signal transformation (temperature radiation = measurement value) for pyrometers and thermography systems is similiar and refers to the identical physical principles. Radiation/ infomation visible to the naked eye predominantly consists of reflected light.
Measuring the invisible
Test object's "natural glow", in terms of thermal radiation at room temperature, is invisble to the naked eye. Reliable calibration consider the corresponding surface temperature emission ratio. "Real" radiation standards emit only a fraction of the black body's radiation. Deviation is defined by the emission factor. The emisson factor is dependent on material, surface texture, temperature and wavelength. esz AG refer to radiation standards at an emission factor of e=0,95.
Calibrating Temperature Wells, Bathes and Climatic Test Cabinets and Climate Chambers
The currently most accurate method in charaterizing temperature sources or temperature testing equipment, e.g. block calibrators, is utilizing platinum-palladium differential thermocouples to evaluate axial homogeneity. The technique complies best with calibration directive DKD-R 5-7 (block calibrator calibration) and subsequently is considered the predominating practice. Calibration procedures for climatic chambers refer to DKD-R 5-7. Temperature test cabinet's characteristics are determined to evaluating nine different test points, evenly distributed among the testing cabinet, in order to identify stability and inhomogeneity. Mobile block calibrators are available to calibrate thermometers and temperature test & measurement equipment on-site.
Calibrating Relative Humidity
Calibration for temperature recorders, temperature loggers and temperature test equipment is performed in stabilized humidity airflow climatic generators. The corresponding calibration standard is a highly precise dew point transmitter enabling tracability in consideration of thermodynamic correlation, absolute humidity and temperature. Continuous evaluation of quick response capacitive precision humidity sensors is realized simultaneously.
Reflectivity at equilibrium
The dew point hygrometer is a measurement instrument (hygrometer) designed to determine water's dew point in air. The dew point is refered to as the point of time resulting in condensate formation. Dew point measurement is performed applying a heated mirror and tied to the fundamental principle of direct measuring. The mirror's reflectivity is measured at dew point, i.e. at time condensate is formating and starting to appear on the mirror.
esz AG' field thermodynamic calibration is specialized in calibration for:
Thermometer / temperature test equipment / temperature probes / temperature calibrators / dry well calibrators / thermo couples / climatic cabinets / gas analysis equipment / humidity test equipment / dew point meters / pH meters / conductivity meter / IR-thermometer