DC Gaussmeter Model 1

 

The strongest rare-earth magnets have a field strength (flux density) of up to 14,000 gauss in a gap configuration.  With a range of 19,999 gauss, the Model 1 gaussmeter can easily measure the strength of any type of magnet in any configuration.  Basic accuracy is +/- 1% of the reading at room temperature, or +/-2% of reading in the full temperature range of 30° F – 110° F (-1° C to 43° C). With a large 4 ½ digit display, the Model 1 has a resolution 10 times better than 3 ½ digit meters; you can measure a change of one gauss in the 19,999 gauss range.  This allows you to measure very small fractional changes in a magnet’s field.   These changes result from slight damage to the magnet or even from small temperature changes in the magnetic material.  A second range of 1999.9 gauss has a resolution of 1/10 gauss.  Turn-on is immediate, and the display updates four times a second.  There is normally no need to rezero, unless you manually want to add up to +/- 10 gauss to the reading, using the “OFFSET” knob.

 

The probe is at the end of a 1-meter (40”) non-detachable and very flexible cable and it does not need recalibration for at least 10 years to remain within specified accuracy.  This external probe is only .060” (1.5 mm) thick and can be placed precisely on any region of a magnet or inside a gap.  The actual sensitive area is 2mm back from the end of the probe and the measurement direction is parallel to the .060” (1.5mm) thickness of the probe.  The actual sensor area is a square only 1/5mm on a side.  (This is a 1-axis meter; that is, the gaussmeter reads a single component of the field, which is itself a vector.  If the probe is placed with the flat surface against the south pole of a magnet, for example, the meter will display a negative number [negative = south] equal to the field strength in gauss of the vector component of the field perpendicular to the face of the magnet there.  If the probe then reoriented so it is not flat against the face, the meter will display a smaller number than the actual field strength because the field at a pole face of a magnet is generally perpendicular to that face.)

 

When measuring the surface of magnets, magnetic gaps, or the field inside solenoids, a small external probe on a flexible cable (such as that of the Model 1) is essential so that you can place the sensor exactly where you want to.  Although absolute error at room temperature is as much as +/-1% of the reading, this gaussmeter can detect fractional changes in the field of a magnetic that are much smaller than 1%.  As long as you place the probe at the same spot on the magnet every time you measure a magnet, you can detect very small deviations in a given magnet from month to month if you suspect the magnet has been weakened (due to overheating, mechanical stress, or demagnetization in an electric motor or an external field).

 

With this meter, you can also compare magnets to see if they are magnetized properly and you can map the magnetic field (or residual magnetism) on magnetized structures.  When doing measurements with a gaussmeter, please note that the actual field at the surface of a magnet is at most one half of the rated residual magnetism for that magnetic material.  If a rare-earth magnet is rated at 14,000 gauss for example, a bar magnet made from that material will have an actual field of at most 7000 gauss at the north pole and -7000 gauss at the south pole.  The readings may be even less than 7000 gauss.  If the bar magnet is thin (that is, its length is at least 10 times its diameter) then the field will be close to 7000 gauss.  If the bar magnet’s length is less than 10 times its diameter, the field at either pole will be weaker.  For example, if the magnet is in the shape of a cube, the surface field will be 4500 gauss or less.  The full 14,000 gauss field can only be created if two bar magnets are in a gap configuration.  This means that the magnets are held close together so that one south pole of one magnet is held very close to one north pole of the other.  The distance between the magnets (the gap width) must be small compared to the magnet diameters, and each magnet’s length must be at least 10 x its diameter.  Then the field in the gap will be approximately the full value of the magnetic material’s residual magnetism, which is 14,000 gauss in this example.  Magnets that are flat (like a pancake) have a very low surface field.

 

The included standard 9-volt battery lasts about 40 hours, and LOW BATTERY indicator shows when about one hour of battery life remains.  A detachable rubberized side cover (boot) is included, as illustrated.  This has a flip-down stand to read the meter more easily when it is on a benchtop or desk.  This meter is warranteed for one year.  (During that time, AlphaLab Inc. will pay for standard shipping back to us and for return shipping to you.  The warranty time is then extended by the amount of time the meter was not in your possession.)   A NIST certificate is not included.  Although calibration is normally not required within 10 years, we can perform a calibration on this meter at any time for $30.  This calibration will include a NIST-traceable certification, and the calibration/cert can also be ordered initially with the meter.  Accuracy of the meter is still guaranteed to within +/-2% even without optional calibration/cert. 

 

Model 1 DC Gaussmeter: $260 (US dollars).  BUY IT NOW

Price includes shipping in the US. For shipping to Canada by USPS add $20 (US dollars). Outside the US and Canada add $40 (US dollars). 

Optional Model 1 DC Gaussmeter calibration certificate: Add $30 (US dollars).

Warranty for this meter is one year. Made by AlphaLab, Inc. (USA).