General Technical Information
Calibration
Gravitas maintains a certified reference magnet that is traceable to a standard maintained by the National Institute for Science and Technology. Calibration of the reference magnet was performed by Magnetic Instrumentation Inc. of Indianapolis, Indiana.
Comparison to other gauss meters
How does the Spin Doctor design compare to other gauss meters? What are you NOT getting?
Those other meters have 1) a fancy carrying case 2) finer resolution down to .1 gauss or less 3) an industrial-strength enclosure, 4) the sensor is on a wand with a cable, 5) ability to change the units to teslas or milli-teslas, 6) an AC field measurement capability in addition to DC. 7) plug-in as well as battery operation.
These features are nice, but they add to the cost, and are often not needed for routine testing of products containing permanent magnets.
Battery Life
The Spin Doctor uses ultra-low power electronic components. The one necessary exception is the hall-effect sensor on the probe tip. Normally it would deplete a set of batteries in a few hours of usage. The software in the Spin Doctor takes a measurement about 5 times a second, but it shuts down the sensor in-between readings so it is only active about 1% of the time. This results in tremendous power savings and a battery life of over 100 hours of continuous usage.
The Spin Doctor E.R. uses a sensor with a wider range that draws somewhat more power, but still provides a battery life of 72 hours continuous usage.
The correct way to install batteries and the battery tray:
Calibration
Gravitas maintains a certified reference magnet that is traceable to a standard maintained by the National Institute for Science and Technology. Calibration of the reference magnet was performed by Magnetic Instrumentation Inc. of Indianapolis, Indiana.
Comparison to other gauss meters
How does the Spin Doctor design compare to other gauss meters? What are you NOT getting?
Those other meters have 1) a fancy carrying case 2) finer resolution down to .1 gauss or less 3) an industrial-strength enclosure, 4) the sensor is on a wand with a cable, 5) ability to change the units to teslas or milli-teslas, 6) an AC field measurement capability in addition to DC. 7) plug-in as well as battery operation.
These features are nice, but they add to the cost, and are often not needed for routine testing of products containing permanent magnets.
Battery Life
The Spin Doctor uses ultra-low power electronic components. The one necessary exception is the hall-effect sensor on the probe tip. Normally it would deplete a set of batteries in a few hours of usage. The software in the Spin Doctor takes a measurement about 5 times a second, but it shuts down the sensor in-between readings so it is only active about 1% of the time. This results in tremendous power savings and a battery life of over 100 hours of continuous usage.
The Spin Doctor E.R. uses a sensor with a wider range that draws somewhat more power, but still provides a battery life of 72 hours continuous usage.
The correct way to install batteries and the battery tray:
Polarity
Polarity is verified on each meter using a reference magnet that has been checked against a known working compass. As the earth's magnetic field is such that the magnetic pole closest to the north geographic pole is actually a magnetic south pole [1],[2],[3], and given that opposite poles attract, the end of a compass needle marked N is truly a north magnetic pole. The photo below shows the Spin Doctor correctly identifying the north-seeking end of a compass needle as a north pole.
Polarity is verified on each meter using a reference magnet that has been checked against a known working compass. As the earth's magnetic field is such that the magnetic pole closest to the north geographic pole is actually a magnetic south pole [1],[2],[3], and given that opposite poles attract, the end of a compass needle marked N is truly a north magnetic pole. The photo below shows the Spin Doctor correctly identifying the north-seeking end of a compass needle as a north pole.
- Serway, Raymond A.; Chris Vuille (2006). Essentials of college physics. USA: Cengage Learning. p. 493. ISBN 0-495-10619-4.
- Emiliani, Cesare (1992). Planet Earth: Cosmology, Geology, and the Evolution of Life and Environment. UK: Cambridge University Press. p. 228. ISBN 0-521-40949-7.
- Manners, Joy (2000). Static Fields and Potentials. USA: CRC Press. p. 148.ISBN 0-7503-0718-8.
Technical Bulletins
December 20, 2012 -- Oxidation on battery contacts. -- One meter was returned for service when the display started acting up, right after new batteries were installed. Sometimes garbage characters were displayed, sometimes nothing at all. It turned out that the negative battery contact, which is a large domed solder pad on the circuit board, had turned dark with oxidation. Once it was cleaned, the meter worked fine. It is recommended that the contact be cleaned with a few swipes from some ultra-fine/very fine sandpaper at each battery change, or anytime the display misbehaves. This applies to both the Spin Doctor and Spin Doctor E.R. meters.