Resistance laboratories provide the measurement traceability for resistance as well as development and maintenance of national physical standards for resistance. The laboratories provides calibration measurements with capability from 1 mΩ to 1 TΩ. The National Standard of Resistance is a 1 Ω and 10 kΩ resistors kept in an oil bath at temperature of 23°C ± 0.001°C. The reference standard resistor is calibrated at BIPM on a regular schedule and disseminate to other resistors by using the automated DCC bridge at range of 1 mΩ to 10 MΩ. Resistance values below 1Ω achieved by using Direct Current Comparator Bridge with a Range Extender. The system has ratios up to 1000:1 with the relative uncertainty of 10-6. The resistance values from above 10 MΩ are scaled up using a modified Wheatstone bridge by replacing Resistive arms with 2 DC Voltage. The resistance laboratories dissemination, capability and uncertainty are shown in following table and diagram respectively.
|
DC Resistance |
: |
|
 |
|
Best Measurement Capability |
: |
±0.5 mΩ/Ω to ± 585 mΩ/Ω |
1 Ω standard resistor |
|
DC Current Shunt |
: |
|
|
|
Best Measurement Capability |
: | ± 5 mA/A to ± 100 mA/A |
