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| Mastech MS5308 LCR meter with ESR measurement - on discount at the moment |
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| Shock:
Another great video John. Good to know its in your power supply somewhere, better than a faulty meter. Wonder if its a 120v 60hz problem (despite the rating) you checked the caps right? :P Anyone else who has one of these confirmed the problem running on mains with the supplied power supply? |
| SeanB:
It needs moving the positive lead direct onto the cap, along with placing a ferrite bead on the diode lead, along with a snubber over the diode. A 100n ceramic cap across the big secondary one as well will help, though for best noise removal you need a 3 pin power lead with the earth connected to the output negative, along with 2 1n class Y caps on the input side from the bridge + and - to earth. That will get rid of most of the noise. Better though is to use this for another purpose ( run a light from it) and build a new unit with a mains transformer, bridge and voltage regulator on the output. As the meter uses less than 100mA it will be both cheap and small. You can repurpose a standard magnetic wall wart and place the regulator on it's output. |
| rowifi:
I've just taken delivery of the MS5308, and checking some small ceramic caps ( 10uf Hicap )using the tweezers notice that the capacitance measures quite different between the frequency ranges ( 6uF ... 14uF ) - and not in a linear way. I haven't had a chance to do any other checks yet but would be interested in any comments, and suggestions on best way to check calibration when I don't have a reference LCR meter. Instructions are poor, but general unit and accessories appear nice. Rob |
| PA4TIM:
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. ESR is just one function. Not specified or a standard, everyone can call his cap low ESR. You need a datasheet to use this value so many digits is useless, if you really need that you need an vectoril impedance meter that makes freuency sweeps or read more about theory and think again if you need it. Also in tht case you never meaure in circuit, only if you have a high vslue you know for sure it is bad, a low value does not proof a thing. There can be others parallel ( coil, reistors, fuses, transformers, other caps ect). Important too is capacitance and for most DC leakage and DC bias. Most datasheets give ESR for 1 KHz or lower and Impedance for 100 KHz. Many ESR or LCR meters do not measure ESR but impedance. My home made ESR meter measures real ESR from 10 KHz to 100 KHz, but I had it working upto 300) it measures caps from 100 nF to over 15000 uF ( han no bigger ones) just 3 ICs, kelvin technique and a few dollars in cost. Checked it against two VNAs, a peak ESR meter and several HP and GR meters. |
| KD0CAC John:
PA4TIM , could you give some more details on your home made meter ? Thanks |
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