Topical summary #1
Development VES instrument
Recently, a prototype of an affordable VES device was developed for use in developing countries on behalf of Practica Foundation. VES - Vertical Electrical Sounding - is a geophysical measuring principle that maps the conductivity of soil layers by means of a current injection into the soil and ground potential measurements. To obtain information about the different types of soil as a function of depth, multiple measurements are made at different electrode distances. » read more.
My LeCroy recovery story
My LeCroy LT344L oscilloscope, the driving force behind this website, was very very ill. At first it took a long time to boot and later it booted not at all anymore. The firm I bought the scope 17 years ago guessed after consulting with LeCroy that it was probably a power supply problem and refurbishing would cost several thousand euro's. And they could not guarantee its future lifespan. Thats a considerable risk. I decided to try to fix this problem myself. Read here the story of my struggles. » read more.
New wattmeter project
As a result of the popularity of the DIY Arduino Wattmeter and questions about additional functionality, the idea arose to design and produce a more practical wattmeter. This product will be developed in collaboration with the embedded software company Embiant. Once a satisfactory design and prototype is ready, it will be made available by a Kickstarter project.
The first ideas about the requirements and functionalities are the following: » read more.
Thermoelectric voltages of shunt resistors
Be careful when selecting a resistor for your shunt when low burden voltages are required. Beside the temperature coefficient, the thermoelectric voltages will have its influence in such applications. By the use of different materials whence the shunt resistor is manufactured and the connecion with the PCB, thermocouplers are created. Temperature differences between the terminals cause voltage differences which are the source of offset voltages. » read more.
True RMS or a true lie?
The two true RMS multimeters who I'm using on a daily base measure the RMS-value in the AC voltage and current ranges. The DC-ranges measure the mean value. Nothing remarkable at first sight. Still, something curious is going one here. As the 9 volt direct voltage of a battery is measured with the multimeter in the AC-range in order to determine the RMS-value, the meter will read 0 volts. The direct voltage will be blocked. This is naturally what is expected when measuring the AC-portion of a signal with the AC-range selected. » read more.
Chinese peltier coolers
Occasionally small components has to be cooled when doing measurements on them. A peltier element can fulfill this task if the demand of cooling power isn't very exacting. A decade ago where these peltiers very expencive, but nowadays cheap Chinese peltiers are dumped on the market. So, i ordered a couple and did some tests to check there performance. I mounted one on a CPU-cooler and powered was a little disappointed of the minimum stable achievable temperature of -10ºC. This was at a reduced power setting of 33 watt. » read more.
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