**HLab 12 (online). Calibrating a Hall Probe**

**Goals**

- To use a Hall probe to sample the field of Helmholtz coils
- To determine the calibration curve for a two-axis Hall probe in the radial mode

**Equipment
**HE1-A Hall Probe

Set of Helmholtz coils

2 Multimeters

Constant current supply

Hookup wires

Ruler

In order to perform an absolute calibration of the device, you must put the probe in a known magnetic field. The best available source of a known magnetic field is a set of Helmholtz coils. This configuration is used to create a nearly constant magnetic field in the region around the point midway between the coils.

**Method
**Work in a group of 2 or 3 people. All work must be done as a group. While you work, check each other out to
make sure the probe is being positioned correctly and the meter is being read
correctly. You'll enter some results online, so you'll need to have this
page open on at least one computer while you're working. Enter all
partners' names now.

*Continuing Part B*...

- Switch the Hall probe to radial mode and re-zero it.
- Carry out your calibration method, recording your measurements in Graphical Analysis as you take them. Give your column headings descriptive names for the variables with units and set the number of decimal places to the appropriate values. If you don't know how to do this, ask.
- In a textbox, write the name of your group. Write the serial numbers of your coils and probe. Also write the equation that you will use to calculate the theoretical field magnitude of the coils. See your result from the Helmholtz coil homework problem.
- Create a new, calculated column for the values of magnetic field calculated using the equation from 4.
- When finished taking your data, turn off the current supply and disconnect all wires. Have the instructor check your station.

**Analysis**

- In Graphical Analysis, plot B vs. V. Perform a linear fit. Title your graph properly and by all means remove the connecting lines. If you don't know how to do this, ask. In the text box, rewrite the fit equation in terms of physics variables B and V, and the values of coefficients with units.
- Save your file with the name hlab12-groupname.ga3 and email it to your instructor.
- Email copies of the GA file to all group members.