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date	article	author	comment
21 mei 2019 17:05:55	Measuring capacitance and ESR	Mykeil	Hi. Great tutorial. I found small mistake. Sin(phi) should be in a formula of Xc calculation in Method 1: Measuring capacitance. Otherwise it will not give 27.974kOhm, as written. Thank you, Regards :)
09 mei 2019 11:07:46	Measuring three-phase power	mohammed	why it is important to use the correct equipment when measuring three-phase power?
04 mei 2019 12:17:45	Extreme low voltage oscillator	Jindra	I would argue that putting two BF245A in parallel does not increase gain. Contrary to what you suggest, their transconductance (measured in mA/V) must be average of individual gm of each of the two JFETs. On the other hand, BF245A has very low drain current at Vgs = 0V (according to data sheet, between 0.5 and 2.2 mA). By putting two BF245A in parallel you increase the current and that probably enables the oscillations to start. In other words, the initial resistance between Vin and the coil is lower. You could probably achieve the same by using a single BF245B or BF245C. However, using two JFETs in parallel will allow for higher maximum drain current and power loss. I think it is a good idea. Maybe I would try 2x BF245B in parallel and look if the output improves.
22 apr 2019 12:12:59	Measuring capacitance and ESR	Freddy	Yes, it is certainly possible to determen the distance of the plates by measuring the capacitance. But be aware that the capacitance is very small: at a distance of 0.1 mm the capacitance is only 8.85 pF! 100 Hz or even 10 kHz is too low to do it reliable. Even at 1 MHz the reactance is 18 kΩ, but feasible.
21 apr 2019 01:46:35	Measuring capacitance and ESR	Daniel	I'd like to measure the distance of two narrow metallic plates with size around 1cm^2 and 1cm^2 at a frequency of at least 100Hz, preferably rather around 1-10 kHz. I think measuring the capacity is the best way to measure the distance. (I have a good microscope to measure the precise distance, but is is very slow. However, it is suitable to calibrate a fast method.) Which of these method do you suggest to measure the capacity? Or none of them?
19 feb 2019 16:20:21	Magnetic permeability	Freddy	First you say you're changing the core material, now you say the material is (and stays?) air?. And why would you measure the permability of air? Are you using the circuits and calculations given in this article?
19 feb 2019 15:26:43	Magnetic permeability	Costa	I'm measuring voltage, the core is air, the inductance of coil is 90uH with air in the core, should i build a coil with higher inductance?
15 feb 2019 00:20:07	Magnetic permeability	Freddy	What are the measured values: current and voltage? Has the core an air gap?
14 feb 2019 15:17:51	Magnetic permeability	Costa	Hi, thank you for this excelent article. i built this circuit with a resistor ( 10-100 ohms ) and a inductor, with a frequency of 100hz to 500 khz. I changed the core material but the voltage of a inductor didn't vary for any frequency. what can i do?
11 feb 2019 15:47:40	Additive synthese waveform generator	Bing	Version 71.0.3578.98 (Official Build) (64-bit) This is the chrome version I have. It's a work laptop. I don't think I can update it. :-( It's working now. :-)