I think it’s fun to know the altitude where I am. While travelling, it’s difficult to pay close attention to the elevation of each moment, and this graph allows me to see where I have been in elevation. I can enjoy the peaks and valleys of my journey, even if I wasn’t able to view the readings at those particular moments.
This article describes a Hall-effect based magnetometer that uses an inexpensive analog Hall-effect sensor, an Arduino, and LCD. The linearity of the magnetometer is surprisingly good when compared against a commercial magnetometer. This unit can be operated manually or make measurements under computer control, so we’ll use our magnetometer in a computer-controlled setup to measure the BH-curve of small sample of magnetic material.
This November, in Versailles, France, representatives from 57 countries are expected to make history. They will vote to dramatically transform the international system that underpins global science and trade. This single action will finally realize scientists’ 150 year dream of a measurement system based entirely on fundamental properties of nature. The International System of Units — informally known as the metric system — will change in a way that is more profound than anything since its establishment following the French Revolution.
Sometimes I wonder which of my portable digital voltmeters I can trust — the B&K, Fluke, or Amprobe. Usually, they’re pretty close but it bugs me not knowing whether they are right on the nose. Fortunately, these days, there are a number of very accurate voltage reference circuits that you can build or purchase for a few dollars.
Small Geiger-Müller (G-M) tubes make ideal sensors for pocket-sized devices to detect radioactivity. However, even a small G-M tube needs an anode voltage in the 400 to 600 volt region. Here's how to generate that voltage from a 9 V battery.
