الفهرس 
COVEROnly 14 pages are availabe for public view
 |  | from | 270 |  |  |
| | | from | 270 | | |
Abstract
For accurately investigate the capability of the capacitance and
inductance laboratory at NIS, this work describes a recent study on
the performance of two types of accurate measuring methods,
namely the classical bridge method and the electronic method.
These methods are represented by three instruments that measure
the standard capacitors and standard inductors. The first method
is based on using both of the precision capacitance bridge assembly
and the precision inductance bridge assembly. On the other hand,
the second method makes use of the precision LCR meter. All these
instruments are available in the capacitance and inductance
laboratory at the National Institute for Standards (NIS), Egypt.
All of the bridge assemblies depend on one of the classical methods
of measuring. The bridge method is based on comparison between
the voltages and currents of the measured unit and a reference
standard unit until a condition of balance is reached.
The precision LCR meter depends on electronic method of
measurement which applies a default value of voltage across the
measured unit. Then, it measures the voltage across the measured
unit, the current flowing through it, and the phase angle between
them. These three measurements are used to calculate several
parameters which describe the measured unit.
Accurate measurements and calibrations of a group of standard
capacitors and a group of standard inductors are carried out
precisely through this study at two different frequencies (50 Hz and
1 kHz). All precautions have been performed which minimize the
resulted error, such as the effect of temperature, humidity,
electromagnetic interference ….etc. The uncertainty statement was
reported for the measured values of capacitances and inductances
according to the requirements of the international standard
ISO/IEC 17025.
The measured values from both the bridges and the LCR meter
show that the uncertainty of measured values of the instruments at
Abstract1 kHz frequency is much better than the accuracy of measured
values of the instruments at 50 Hz by more than double.
The measured values at different frequencies and the investigated
expanded uncertainties fairly demonstrate that bridges show high
accuracy and less uncertainty of measured values at both
frequencies. The precision LCR meter, although it is more recent
and more sophisticated provides less accurate results. Even, the use
of this meter saves time, effort and cost.
It was deduced that the NIS, Capacitance and Inductance
laboratory finally has a level of uncertainty for inductance
measurements better than 5 mH in range of Henry, 5 μH at milli-
Henry range, and 20 nH at range of micro-Henry for 1 kHz
frequency and a level of uncertainty better than 10 mH in range of
Henry, 10 μH at milli-Henry range, and 25 nH at range of micro-
Henry for 50 Hz frequency.
Also, It was deduced that the NIS, Capacitance and Inductance
laboratory has a level of uncertainty for capacitance measurements
better than 0.7 fF in range of pico-farad, and 1 nF in range of
micro-Farad for 1 kHz frequency and a level of uncertainty better
than 10 fF in range of pico-Farad, and 3 nF at range of micro-
Farad for 50 Hz frequency.