UNI-T UT61E capacitance measurement inaccuracies ?

[warrior_]

Yesterday i received my new UT61e from ebay and the capacitance measurement gives two different values on the same cap with autorange and manual ?
Also the idle value with nothing connected on auto reads around 0.286 nF ?


1000 uF 12V on auto reads  0.9108 mF
on manual (2 presses) reads 0.881 mF

im confused its seams like my caps are bad and good at the same time

I have a youtube video of the measurement , can anybody explain what is going on ?


https://www.youtube.com/watch?v=XKrToVdBgbo&feature=youtu.be

[torr032]

Yes I saw on taobao, buyers are complaining something about capacitance with this new model with improved input protection. On old model it should be 60 pf ghost capacitance no leads connected, on new one it is higher around 300 pf.

Where did you bought it, if it is from ebay can you tell from what seller?

[warrior_]

Yes its the new model, i bought from geiliable-store.
Is there any fix or hack for this and what is causing the fluctuations


this is the new pcb layout

[PA4TIM]

A multimeter is no LCR meter. Most multimeter charge a cap with DC and measure the time it takes. Try it again but short the cap before the measurement. If it holds charge from the first measurement the second one will be wrong.
Besides that it also gets fooled by ESR. Increasing ESR and decreasing capacitance can cancel each other out so the cap looks good but is not.

But hey, better as nothing and do not expect to much, it is a Unit-T 

[Wytnucls]

By pressing 'Manual' twice, you end up on a higher range, with a shorter charging cycle and less accuracy.

Protection is still to a low standard. No spark gaps or MOVs, no fusible resistor and same old 250V fuses.

[PA4TIM]

http://www.pa4tim.nl/?p=3331
At the bottom of this page I made about cap testing is the result of a test on several bad caps measured in several ways by a tv repairman and in several ways by me.

[warrior_]

These are capacitance specs for UT61e.
Can somebody confirm that the new version UT61e is out of spec ?

[Wytnucls]

Brand new electrolytic caps can be 20% out on capacitance, so get an LCR meter if you want the true value, measured at 120 Hz, like the datasheet says.