Probe Sensitivity And Measuring Ranges; Probe Accuracy - Magnet-physik FH 55 Operating Instructions Manual

Gauss- / Teslameter

6.5 Probe Sensitivity and Measuring Ranges

As the H 54 is covering a wide field strength range, probe with different sensitivities are
necessary You can find the standard probe types on the Magnet-Physik homepage
http://www.magnet-physik.de.
The user of a field strength meter can have difficulties in choosing the best probe. Therefore,
please find below some simple rules that can help making the right choice.
1. Choose a probe that matches your application. Do not buy more accuracy, ranges or
sensitivity as necessary.
2. The thinner a probe is, the more fragile it is. Overcome the temptation buying a probe that
can be easily damaged for just a possible future application. Avoid using a probe with an
exposed Hall generator for general field strength measurements. If the probe stem or sensor
is damaged, the probe cannot be repaired.
3. Be careful when using metal covered probes for measuring AC magnetic fields. Eddy
currents in the cover can impact the accuracy of the measurement or even unduly heat a
probe. Probes with a stem made of fiber-glass enforced epoxy are a good choice for AC
measurements.
4. Different stem lengths are offered for the most probes. The operator's demands and the
dimensions of the measurement set-up influence the final choice. Long probes are easier
broken away.
5. Take notice of the different active areas of the probes. These are given in the data sheets. A
Hall sensor measures the average of the field, taken from the total active area of the probe.
Chase a probe with a small active area if you want to measure a field with a high gradient
over the sensor width.
6. Our probes cover different field strength ranges that can be used. Check the data sheets for
the required ranges. High field probes are specially calibrated for use above 3 T (30 kG).
High sensitivity probe work in the ranges from 30 µT (300 mG) to 300 µT (3 G).
7. If none of the standard probes matches your configuration, keep in mind that Magnet-Physik
also can make customized probes for fulfilling special demands regarding dimensions,
temperature range or accuracy. Please contact us with the details of your application.

6.6 Probe Accuracy

The user must consider all the possible contributors to the accuracy of the reading. Both the
probe and gaussmeter have accuracy specifications that may impact the actual reading. The
probe should be zeroed before making critical measurements. The zero-probe function is used
to null (cancel) out the zero offset of the probe or small magnetic fields. It is normally used in
conjunction with the shielding chamber, but may also be used with an open probe (registering
the local earth magnetic field). Users wishing to cancel out large magnetic fields should use the
Relative function.
Probe temperature can also affect readings. To help offset the effects of temperature on the Hall
sensor, a thermistor is included in some probes.
Probe readings are dependent on the angle of the Hall sensor in relation to the magnetic field.
Maximum output occurs when the flux vector is perpendicular to the plane of the sensor. This is
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