Quantum Hall Resistance System

During the period of November 7th, 2003 to November 14, 2003, Measurements International successfully installed our first commercially available transportable Quantum Hall Resistance System at the National Physical Laboratory in New Delhi, India.

The model 6800 is the first of its kind. It provides an economical means of maintaining an accurate and stable representation of the ohm with a precision <2 x 10 -8.

The system is cryongenically and electrically easier to operate than previous systems. The model 6800 is transportable throughout the laboratory, and one fill of the helium will last for 6 days.

Installation of the Quantum Hall Resistance System was completed in less than one day.

The cryostat was evacuated and flushed with helium gas.

The cryostat was then filled with liquid helium and allowed to cool down for several hours.

The probe space was then continuously pumped to drop the temperature to 1.2K.

A series of checks were then performed to ensure that the sample was operating correctly. These checks consisted of a sweep check as the magnet was ramped up, dissipation checks on the i = 2 plateau and contact resistance checks.

A 1k Ohm resistor of known value was compared with the Quantum Hall Resistor of the model 6800. The value obtained agreed to < 2 x 10-8 (1.1 x 10 -8) with the expected value.

Each step of the installation and measurement was done slowly and was repeated to ensure proper training of the NPLI staff.

Once the QHR value was transferred to the 1000 Ohm standard, an automated program was set to build up and down to calibrate

the 10,000 Ohm and 1 Ohm in terms of the Quantum Hall Resistance.

For more information on the Model 6800 Quantum Hall Resistance System, please download the attached PDF.

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