RESISTIVITY AND HALL EFFECT MODULE

The Resistivity system is configured for 4-terminal resistance measurements and Hall voltage measurements in the range μΩ to MΩ resistance. Automation of the system under the LabVIEW operating environment provides not only system parameter control but also data acquisition and processing of raw data. ASCII data files are provided for ease of subsequent manipulation. Provision is made for scanning up to 5 samples at a time during a single sequence of measurements is offered as an option.

The resistance is measured by a separate DVM and current source. The applied voltage can be dynamically reversed in order to subtract thermal potentials, and the measurement averaged. For each measurement the current will be set at a low level and increased to provide an adequate measurement voltage. The maximum current, power or voltage on the sample can be preset to avoid sample heating and/or damage.

As each measurement is performed the magnetic field and temperature are varied according to a pre-arranged sequence. Different sequences can be stored and drawn down by command, which generally simplifies operating procedures making the system easy to use without a detailed knowledge of the system software and hardware.

Resistivity and Hall Effect Specifications:
- Two Keithley Instruments are used to provide a current source and voltage measurement. The current source type 2400 provides currents over the range 1 nA to 1 A.
- The voltage measurement DVM type 2182 provides measurements over the range 100nV to 10V.
- Between these two instruments, resistivity over the range 109 ohm to 10-7 ohm are covered.
- Accuracy 0.01% typical except at the extremes of the range settings.
- A scanning facility is provided.

Our resistivity sample platform is designed to go inside the VSM pickup coils for ease of change between measurement options and has 8 electrical connections for up to two samples (up to 5 samples on request).

Key features:
• Applied DC current can be reversed to eliminate thermal potentials.
• Maximum current, power or voltage on the sample can be pre-set to avoid sample heating and or damage.
• For each measurement the current is normally set low and increased to provide an adequate measurement voltage

Maximum sample size: 10mm diameter
Resistance measurement range (DC): 10-7 to 10^9 Ohms
Voltage sensitivity (DC): 1V to 0.1μV
Accuracy of resistance measurement: < 0.1% 1-10^6 ohm