{"id":661,"date":"2026-04-29T19:11:02","date_gmt":"2026-04-30T03:11:02","guid":{"rendered":"https:\/\/salemdata.net\/johnpress\/?p=661"},"modified":"2026-05-01T08:03:25","modified_gmt":"2026-05-01T16:03:25","slug":"t-beam-magnetometer-investigation","status":"publish","type":"post","link":"https:\/\/salemdata.net\/johnpress\/?p=661","title":{"rendered":"T-Beam Magnetometer Investigation"},"content":{"rendered":"\n

5\/1\/2026 – Update<\/strong>: over 100k hits on my Forgejo server, presumably bots, so I now require sign-in to explore.\u00a0 Contact me if you want an account.<\/p>\n

Introduction<\/h1>\n

This is a deep technical<\/em> dive, possibly only of interest to people programming the LilyGO T-Beam SUPREME.\u00a0 Much of the working below are snippets taken from Wikipedia.\u00a0 What’s important is that if you want the T-Beam to serve as a compass and compute bearings, you need to have an accurate heading (like a compass would give you).<\/p>\n

Executive Summary<\/h2>\n

Calibration must be performed per device if you plan to using bearings derived from the magnetometer. In testing across seven T-Beam units, inter-device variation far exceeded environmental variation, demonstrating that factory or shared calibration constants are not viable.<\/p>\n

T-Beam’s Magnetometer<\/h1>\n

The LilyGO T-Beam SUPREME Specifications<\/a> states that there is a “Magnetometer: QMC6310” sensor.\u00a0 “A magnetometer<\/b> is a device that measures magnetic field<\/a> (B<\/b><\/span>) [see below “The B Field”] or magnetic dipole moment<\/a>. Different types of magnetometers measure the direction, strength, or relative change of the magnetic B<\/b><\/span>-field at a particular location. …A compass<\/a> is one such device, one that measures the direction of an ambient magnetic field, in this case, the Earth’s magnetic field<\/a>.”\u00a0 QMC’s data sheet states that the 6310 measures gauss units (Symbol G<\/strong> for gauss) which is a unit of measurement of magnetic flux density<\/a>, \u00a0 Gauss units are the older system of measurement which was superseded in 1961 by the International System of Units<\/a> (SI), the use of the gauss has been deprecated by the standards bodies, but is still regularly used in various subfields of science, and preferred in astrophysics<\/a>.[<\/span>1]<\/span><\/a><\/sup>\u00a0 \u00a0Case in point: the QMC6310 uses gauss (G<\/strong>) units.\u00a0 The SI unit for magnetic flux density is the tesla<\/a> (symbol T),[<\/span>2]<\/span><\/a><\/sup> which corresponds to 10,000gauss.<\/p>\n

Therefore, one must bear in mind that there are two kinds of units, gauss, B<\/strong>,\u00a0 and tesla, T<\/strong>, used in this arena.<\/p>\n

The B Field<\/h2>\n

The magnetic B<\/b><\/span> field is the “magnetic field” responsible for magnetic forces, magnetic torques and electromagnetic induction; it is also known as magnetic flux density.\u00a0 <\/b>The SI<\/a> unit of B<\/span> is tesla<\/a> (symbol: T).[<\/span>note 4]<\/span><\/a><\/sup> The Gaussian-cgs unit<\/a> of B<\/span> is the gauss<\/a> (symbol: G).[<\/span>8]<\/span><\/a><\/sup> (The conversion is 1\u00a0T \u2258 10000\u00a0G.[<\/span>9]<\/span><\/a><\/sup>[<\/span>10]<\/span><\/a><\/sup>)<\/p>\n

The QMC6310<\/h1>\n

The QMC6310 has a required “mode” setting that sets the limits of its ability to determine gauss counts.\u00a0 There are several, but only two modes are pertinent to the T-Beam.\u00a0 The first mode is 8G which encompasses measuring +8 to -8 G [gauss]\u00a0 QMC’s data sheet specifies that for 8G mode, it has a sensitivity of 3,750.\u00a0 For 2G, the sensitivity is 15,000.<\/p>\n

\"A
QMC630 Data Sheet, Table 2. Specifications<\/figcaption><\/figure>\n

Note: “Typ” = “Typical”<\/p>\n

So, to determine the gauss, for a specified mode, e.g. 8G, you take the “raw” count a particular axis, i.e. “X”, reports and divide 3,750.\u00a0 So:<\/p>\n

\\[
\nB_{\\text{Gauss}} = \\frac{N_{\\text{counts}}}{S_{\\text{LSB\/G}}}
\n\\]<\/p>\n

Where:<\/p>\n