In the electrical calibration laboratory based on the scope of certification and national and international standards of production and measurement of current and voltage AC, DC, resistance, speed, time, sound, phase deviation, capacitance, inductance, AC, DC power, oscilloscope and the temperature sensor simulator is calibrated and measured by experienced and trained experts.
Calibration quantities of electricity such as calibration of dc voltage and the calibration voltage, calibration of flow and calibration of AC, calibration resistivity, calibration frequency and includes calibration of measuring instruments electrical, such as calibration of multiple digital and analogue indication of voltage, current and frequency, Caliper ammeter calibration, oscilloscope calibration,… as well as devices that produce electrical quantities such as frequency and waveform generators, instrumentation simulators,….
Similar to other calibrations, the measurement result (so-called output quantity of the calibration system) and its wide uncertainty are affected by various factors (so-called input quantities). have. Therefore, identifying these factors and how to evaluate their standard uncertainties according to the statistical distribution that they follow and how to combine these uncertainties according to the mathematical model for the calibration system (such as the law of propagation of uncertainties) is very important.
Some influential factors (input quantities) in the calibration of electrical equipment (measurement and production) are:
Calibration of reference equipment or electrical calibration work standards
Uncertainty attributed to the calibration of reference equipment or measurement standards recorded in the calibration certificate and should be converted to standard uncertainty (standard deviation). According to the information in the calibration certificate such as coverage factor, confidence level, type of statistical distribution of the measurement result, number of degrees of effective freedom (for statistical distribution t) and the standard uncertainty of this factor can be easily estimated.
Stability and change of specifications with time
The technical specifications and performance of all measuring equipment change over time (Drift) and this change in electrical equipment is such that their uncertainty is constantly added, so most manufacturers in the technical specifications of reference equipment and operating standards, correct They offer them for 3 months, 6 months and one year.
The technical characteristics of passive devices, such as standard resistors or powerful radio frequency (RF) and microwave attenuators, change slightly over time. Their drift rate should be evaluated based on the values obtained from previous calibrations and since the drift can not be assumed to be linear, the data should be plotted as a control graph in the distance between the two calibrations and its effect over time should be evaluated from the obtained curve. Based on the results of the control diagram, in addition to the amount of drift, the instability due to random factors and the expected accuracy of a measuring device and its calibration period can be determined. In the case of complex electronic devices and active devices, it is not possible to evaluate by the method of passive devices, because changes in their performance at long intervals are random in nature and difficult to predict. The best way to judge whether such standards have complied with their specifications is to control them against inactive standards. Often in the process of calibration of these devices, it is necessary to first adjust on them and then calibrate.
Measurement conditions and conditions of use in electrical calibration
If the environmental conditions of the laboratory are different from those required for the calibration of electrical quantities, environmental influencing factors should be involved in assessing the uncertainty. Ambient temperature is often the most important factor, and therefore knowledge of the temperature dependence coefficient of reference standards or work such as resistance standards will greatly help to correctly assess uncertainty. Changes in the relative humidity of the environment also affect the amounts of uncoated mica inductors and capacitors. The effect of atmospheric pressure on some electrical measurement standards can also be significant.
At radio and microwave frequencies, ambient temperature can affect the performance of, for example, attenuators, impedance standards whose values depend on their dimensions, and sensitive and precise components. Rapid temperature changes or heat shocks that may be applied to devices such as power sensors equipped with a heat compensation system during transport or direct exposure to sunlight or any other heat source may affect their performance.
To assess the uncertainty, it is necessary to consider the possible effects of differences in electrical operating conditions, such as power dissipation, frequency distortion, or voltage level applied to the equipment, with their calibration conditions. Resistance standards, resistor voltage dividers, and attenuators at any frequency are examples of these devices that are affected by self-heating or applied voltage. It must also be ensured that all devices are used within the supply voltage range specified by the manufacturer. The effects of frequency interference and perturbation can affect the amount of alternating signal (AC) used for calibration.
Rose Calibration Company in Melbourne, Australia with over ten years of experience in calibration of different multimeter, appliance tester, high-voltage power provides all calibration, maintenance, and repair services throughout Australia. If you live in Sydney, Melbourne, Adelaide, Perth, Geelong, and Brisbane, you can receive your quote in less than two hours by fill-up the form via the “Booking” link.
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