How does a calibrated Hall Probe work?

[Yoriko]

I'm supposed to plan an experiment using a calibrated hall probe to investigate the relationship between Magnetic field strength (B) of a coil and the distance (x) from the centre of the coil.

I'm supposed to be able to take direct readings from the calibrated hall probe to calculate B, but how to? Is the hall probe supposed to be connected to something else?

[Bob S]

There are several implementations of the linear Hall Effect probes used for magnetic field measurement. The simplest architecture is similar to a Wheatstone bridge, with two terminals for applied voltage, and two for a differential voltage output (floating outputs). The applied dc input voltage should be a regulated voltage, usually 5V or 6V. Use a 7805 or 7806 IC regulator if necessary.The differential output voltage is usually about 0.2 mV per Gauss to 2 mV per Gauss, with an output impedance of several k-ohms. The output voltage usually has a temperature coefficient. These are 4-terminal probes. Use a floating digital voltmeter (battery operated is best) with 1 mV or better resolution, and a 10 meg input impedance.

Some linear probes have a built-in differential amplifier (with some voltage gain) with temperature compensation. These are usually 3-terminal probes, with the output voltage measured with respect to the negative input voltage terminal. For a 6V input probe, the output voltage for zero Gauss is 3V.

Unlike some other probes, like proton nuclear magnetic resonance (NMR), the Hall Effect probes are usually only about ±20% calibration, unless specifically hand-calibrated.

Bob S

[Yoriko]

There are several implementations of the linear Hall Effect probes used for magnetic field measurement. The simplest architecture is similar to a Wheatstone bridge, with two terminals for applied voltage, and two for a differential voltage output (floating outputs). The applied dc input voltage should be a regulated voltage, usually 5V or 6V. Use a 7805 or 7806 IC regulator if necessary.The differential output voltage is usually about 0.2 mV per Gauss to 2 mV per Gauss, with an output impedance of several k-ohms. The output voltage usually has a temperature coefficient. These are 4-terminal probes. Use a floating digital voltmeter (battery operated is best) with 1 mV or better resolution, and a 10 meg input impedance.

Some linear probes have a built-in differential amplifier (with some voltage gain) with temperature compensation. These are usually 3-terminal probes, with the output voltage measured with respect to the negative input voltage terminal. For a 6V input probe, the output voltage for zero Gauss is 3V.

Unlike some other probes, like proton nuclear magnetic resonance (NMR), the Hall Effect probes are usually only about ±20% calibration, unless specifically hand-calibrated.

Bob S

:confused: Hm I'm not taking so high level physics yet so I don't really understand. So basically the hall probe is connected to a Gauss meter so direct readings of magnetic field strength can be obtained?

[MagnetDave]

I'm supposed to plan an experiment using a calibrated hall probe to investigate the relationship between Magnetic field strength (B) of a coil and the distance (x) from the centre of the coil.

I'm supposed to be able to take direct readings from the calibrated hall probe to calculate B, but how to? Is the hall probe supposed to be connected to something else?

It needs to be connected to a meter. Most probes are calibrated to match a given meter.

for instance:

http://www.lakeshore.com/mag/ga/gm410po.html

[Yoriko]

It needs to be connected to a meter. Most probes are calibrated to match a given meter.

for instance:

http://www.lakeshore.com/mag/ga/gm410po.html

Ok thanks! :smile:

[Bob S]

:confused: Hm I'm not taking so high level physics yet so I don't really understand. So basically the hall probe is connected to a Gauss meter so direct readings of magnetic field strength can be obtained?
You could get one of these sensors from AllegroMicro (sometimes available as a free sample) and read it out with a standard digital voltmeter:

http://www.allegromicro.com/en/Products/Part_Numbers/1301/1301.pdf

If you need an absolute calibration better than than the standard specification, make a small electromagnet and do it yourself.

Bob S