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| Mastech MS5308 LCR meter with ESR measurement - on discount at the moment |
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| kripton2035:
--- Quote from: KD0CAC John on January 04, 2013, 02:29:14 pm ---PA4TIM , could you give some more details on your home made meter ? Thanks --- End quote --- explained on his web site here : http://www.pa4tim.nl/?p=3775 |
| KD0CAC John:
Thanks , too bad the hole page does not get translated . The column on the right is not seen by by my Google translate . |
| PA4TIM:
In what would you translate it, it is in English, and i think that is your native tongue ;-) But that is my explanation about ESR, not about the meter. http://www.pa4tim.nl/?p=1728 This is about meters. On the bottom there is a handdrawn schematic. I use a standard voltage panel meter for read out. There is a new version based on this one on its way. It is probably gonna be a kit in the near future, I'm working with some friends on that. ( i have not much experience in pcb drawing so they do that part) and it must be affortable and allthough components are not expensive, all together including display, cabinet ect will make it more expensive like i want. It is not to make a profit, i do not care for that, but it i do not want it to cost me money snd I'm no company so I can not buy big numbers cheap. So the form of the kit will be a questionmark. The changes are small. First i changed the oscillator and flipflop idea because that performance turned out to be component dependend. Then the inverters used to split the signal had to go ( 74LS14 and 04 ( old stock) are tried worked on my proto very welk but on the pcb proto we found out new ones were not consistant in dutycycle, so to much product deppendacy too,) so i thought of a better solution. The oscillator frequency is now doubled. This is no problem at all. Just a bigger potentiometer. Mine runs 20-200KHz. Then I use a 4013 divider to divide the frequency by 2. Very simple, and i have two nice opposite phase signals and a perfect 50 % dutycycle. This setup i made about a month ago and all tests are good now. Now we must design a better pcb, the first one was not up to my wishes and standards. ( I'm an analog guy, the ocb artist is nost times doing digital stuff) To much crosstalk and leakage, to thin traces ect. But the schenatic as it is on the link, will work. But not optimal, but if you find a Parker or Peak meter good, and use it at 100 KHz only this will be more then good enough. With the changes it will be a lot better. |
| KD0CAC John:
The way the site shows up on my computer the column / box on the right is in , I guess your language . Inside the top of the box on the right is the zoeken / search , then below that is the categorieen / category and everything else in that box . It would seem that my automatic search option does not see the box I am referring to ? |
| The Electrician:
--- Quote from: PA4TIM on January 04, 2013, 11:49:05 am ---Capacitance does change with frequency and indeed not lineair ESR too. It is at max at 0.00000000000001 Hz >:D and decreases rather fast until 10-20KHz, after that is goes slowly down and somewhere between 50 KHz and some MHz (depending the package ect) It starts to rise again due to things like skin effect. --- End quote --- I don't find the described behavior of capacitor ESR to be common, especially with respect to aluminum electrolytics. It does seem to be more common with non-electrolytics, but even then it's mostly older capacitors with dielectrics that aren't as good as the modern materials. For example, attached are two images from an impedance analyzer showing the impedance and ESR vs. frequency. The frequency is swept from 50Hz to 5 MHz. The vertical scale is logarithmic with 100 ohms at the top and 1 milliohm at the bottom. In these plots the impedance (Z) is the green curve and the ESR is the yellow curve. The first image shows an old cap with unknown dielectric; it might even be paper. The second image shows a modern MKP capacitor made by WIMA. The ESR is always less than the impedance, and just touches the impedance curve at the capacitor's series resonance frequency (SRF). For a non-electrolytic capacitor like these two, the losses are low enough that the slope of the impedance curve increases substantially as the SRF is approached, with almost a sharp point at the bottom of the curve. Notice that the old cap ESR decreases by about 3 orders of magnitude from 50Hz to the SRF. The ESR of a non-electrolytic capacitor at frequencies below the SRF is typically dominated by the dielectric losses, and with modern dielectrics the variation is not so great compared to the older, inferior, dielectrics. The ESR for the MKP capacitor is so low (3 milliohms at the minimum) that it is difficult for the analyzer to measure accurately. I find that aluminum electrolytics typically don't have much increase in ESR as the frequency decreases to very low values because the non-frequency-dependent losses in the electrolyte, etc., are so great that they dominate. I'm going to start a new thread in the Projects, Designs and Technical stuff forum and post a number of plots of capacitor parameters vs. frequency. |
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