Standard Resistors
At SCL, a Quantized Hall Resistance Standard (QHRS) System has been established as a primary standard for representation of the SI unit of resistance (ohm) based on the von Klitzing constant, RK-90, which was introduced following international agreement and adoption by the International Committee for Weights and Measures (CIPM). The QHRS system consists of Quantum Hall Effect (QHE) samples, a 3He variable temperature sample insert, a superconducting magnet, and an automatic cryogenic current comparator resistance bridge (ACCCRB). Dissemination of the ohm value as represented by the quantized Hall resistance, RH(i), is by using the ACCCRB and other Laboratory equipment, including Direct Current Comparator Resistance Bridge, Kelvin Ratio Resistance Bridge, modified Wheatstone Bridge and other resistance ratio devices. All DC resistance measurements performed at SCL are traceable to the RH(i). Standard resistors in the range 1 m£[ to 100 M£[ can be measured.
For oil-immersed standard resistors, the best measurement uncertainties will be assigned only to 4-terminal decade-valued standard resistors of high quality, and for measurements being made with the resistors immersed in a constant temperature oil bath at 23 ¢J. Measurement at oil temperatures other than 23 ¢J and in the temperature range 18 to 25 ¢J can also be made with additional uncertainties.
Resistors not suitable for oil immersion or of values above 1 MΩ will normally be measured in air at nominal temperature of 23 ¢J with increased measurement uncertainty.
Resistors of non-decade values are measured with additional uncertainties.
Calibration of temperature coefficients for oil-immersed standard resistors is also available. Normally, 23 ¢J is taken as the reference temperature and the temperature coefficients are determined from results of our resistance measurements made at the reference temperature and at 3 other temperatures over the temperature range of 18 to 25 ¢J, using appropriate curve fitting techniques. The resistance value at the reference temperature will also be reported.
Calibration charges
| Fee in HK$ | |
|---|---|
| Measurement of the resistance of a standard resistor with nominal decade value, in range 1 mΩ to 100 MΩ. 1. at one temperature. 2. for each additional temperature (for resistors suitable for oil-immersion). |
$1910 $680 |
| Measurement of the resistance of a standard resistor with nominal non-decade value, in range 1 mΩ to 100 MΩ. 1. at one temperature. 2. for each additional temperature (for resistors suitable for oil- immersion). |
$1920 $680 |
| Measurement of temperature coefficients for an oil immersed standard resistor. |
$4080 |
| Measurement of the resistance for all settings of the first decade of a decade resistance box. | $3170 |
| Measurement of the resistance for all settings of each additional decade of the same decade resistance box. | $1060 |
| Measurement of the resistance of each resistor of a resistor build-up box (Maximum 12 resistors). | $8470 |
