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| ELECTRICAL RESISTANCE AND CAPACITANCE LABORATORY |
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Quantity - Electrical Resistance.
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Unit - Ohm ( ).
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Tasks
of the laboratory |
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The main task of the
laboratory is the realisation and maintenance of the
electrical resistance standards and their scale in
National Standard of Electrical Resistance.
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International
comparisons |
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DUNAMET Project D 9.
International comparison by the PHARE programme PRAQ III
of the European Committee for Standardisation (CEN).
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Available
metrological services |
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Verification of resistance
reference standards og 1.order using a DC (in a range
form 10-4
to 109 ) and 2., 3.
orders (in a range from 109 to 1012 ). Verification
of resistance bridges and resistor decades using a DC,
resistance voltage
dividers, resistance shunts, resistance ranges of
multimeters and calibrators (in a range from 10-4
to 1012 ). Determination of the temperature
coefficient of a standard, in a limited range of thier
loading characteristics and exams of precise operation
meters.Verification of reference standards of 2. and 3.
orders and AC resistor decades at AC (in the range from 1
to 105
at a
frequencies from 80 to 1600 Hz) with an option to
determine their frequency dependance. |
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Methods
of measurement: |
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- a method of direct
comparison with working standards of the SMU or method of
substitution are used in the verification of reference
standards of 1. and 2. orders. Click for
details!
- AC resistors in a range of 1 - 105 are compared
using a direct substitution method with a reference
standard. It is possible to find out the frequency
characteristics for the range of frequencies of 80 - 1600
Hz and time constant of the standard. The relative
combined standard uncertainties for these resistances are
from 1x10-6
to 1x10-5. |
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Instruments
in use |
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DC
comparator bridge with bath and equipment |
National
Resistance Standard (a group of standards consisting of
1 sealed standards and a gropu of
precise 10 k standards). An accuracy of
resistance measurements at the SMU is verified by
a regular comparison of transfer standards 1
and 10 k to value in BIPM (other
comparisons at 1986, 1991, 1996).
Working standards - decimal value in the range of
10-4 to 1010
and combined transfer standards in the range of 1
to 1012 .
DC current comparator bridge produced by Guidline
Co. (model 9920) for calibration of small values
standards (up to 1 k) and calibration of
current shunts pu to 100 A with relative combined
standard uncertainty of direct measurements from
1x10-5 to 1x10-7. Wheastone
bridge produced by Tinsley Co. (model 5577 A) and
a high-value bridge developed in SMU which
relative uncertainties at direct measurements
from 3x10-3 to 2x10-6 in
accordance with used range. Double AC resistance
bridge developed in SMU with indictuvely coupled
ratio arms, with combined standard uncertainties
of resistance measurements from 3x10-4
% to 5x10-5 %. |
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Primary standards of
resistance with a calculate frequency dependence up to
1600 Hz and AC working resistance standards of Tinsley
type 5684 with nominal values of 1 - 10 k.
The laboratories of resistance operated at the basic
temperature of 23°C stabilised within ± (0.2 - 0.5)°C.
The temperature, humidity and atmospheric pressure are
recorder for correction requirements. |
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