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 Post subject: Is my new capacitor within tolerance?
PostPosted: Mar Wed 07, 2018 5:21 am 
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Joined: Jun Sun 14, 2009 10:44 pm
Posts: 443
I'll get to my questions in a sec but first some background:

I got a parts order in from Mouser. So first thing was to convert the inlet to a new IEC C14 socket
on my General Radio 1611-B capacitance test bridge:
Attachment:
IECinlet_r.jpg
IECinlet_r.jpg [ 37.59 KiB | Viewed 432 times ]

Attachment:
1611b_r.jpg
1611b_r.jpg [ 82.01 KiB | Viewed 432 times ]


Next, I tested this freshly Mouser delivered 18uf/450v UPZ electrolytic ( mouser pn 647-UPZ2W180MPD):
Attachment:
UPZ-20uf-450v_r.jpg
UPZ-20uf-450v_r.jpg [ 46.2 KiB | Viewed 432 times ]


And here's the reading I got:
Attachment:
UPZ_testReading_r.jpg
UPZ_testReading_r.jpg [ 37.72 KiB | Viewed 432 times ]


The readings are:

Dissapation Factor (=Tan Delta) = 4.2%
Capacitance = 15.8uF
Test Frequency = 60hz

Meanwhile, the data sheet for UPZ series is referenced to a 120hz test frequency:
Attachment:
UPZ-Specs.JPG
UPZ-Specs.JPG [ 33.87 KiB | Viewed 432 times ]


I suspect the capacitance is within the +/- 20% specification despite testing at 60hz vs 120hz. However I am a little confused about the dissipation factor. My understanding is that the Dissapation factor = Tan Delta which is what is in the spec sheet.

So here's my question: Can I compare the 4.2% reading from the bridge to 0.20 spec in the datasheet? Is it within tolerance? I'm not sure if i can interpret 0.20 as equivalent to 20% since the data sheet doesn't say anything about percent.

Thanks,
Grid2


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 Post subject: Re: Is my new capacitor within tolerance?
PostPosted: Mar Wed 07, 2018 1:15 pm 
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Joined: Jun Fri 19, 2009 6:34 pm
Posts: 7693
Location: Long Island
While most texts simply state that dissipation factor is approximately equal to tan-delta, it has to be remembered that DF is sometimes expressed as a percentage. Same with power factor which is also usually a percentage. Therefore the bridge dial is multiplying the result by 100 to convert it to percent. So your cap is actually measuring a tan-delta of 0.042 which is well within the 0.2 spec given.

It might also be noted that prior to measuring an electrolytic on a bridge, normal practice is to connect it up to DC and let it "soak" at rated voltage for half an hour or so to take care of any reforming that may be needed.

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 Post subject: Re: Is my new capacitor within tolerance?
PostPosted: Mar Thu 08, 2018 5:59 am 
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Joined: Jun Sun 14, 2009 10:44 pm
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Chris108 wrote:
DF is sometimes expressed as a percentage. Same with power factor which is also usually a percentage. Therefore the bridge dial is multiplying the result by 100 to convert it to percent. So your cap is actually measuring a tan-delta of 0.042 which is well within the 0.2 spec given.

That's comforting to know and thank you this was very helpful. This set me on the right path to re-read the 1611-B manual and also find the corresponding and supporting information on Wikipedia about the Dissipation Factor (DF) https://en.wikipedia.org/wiki/Dissipation_factor I now feel comfortable that I am correctly comparing what I read off the bridge to the manufacturer's spec sheet.

What's clear to me now, as Wikipage also indicates, is that " DF is often expressed as a percentage" I also subsequently found in the 1611-B manual "Dissipation factor is indicated in percent on the DISSIPATION FACTOR dial... in all unmodified formulas the dissipation factor must be expressed as a ratio (divide the reading by 100)". Also makes sense to me now that the spec sheet, by using Tan Delta, is presenting a ratio number and not a percentage (i.e. ratio of Series Resistance to Reactive impedance).

Chris108 wrote:
normal practice is to connect it up to DC and let it "soak" at rated voltage for half an hour or so to take care of any reforming that may be needed.
I tried that! I put it on my cap reformer/leak tester for 45 min at 410VDC, fully discharged it and then re-measured. Results were essentially the same - maybe a smidgen hair more capacitance (15.8+ a hair). Would be really difficult to say it moved the needle. So I suppose it really is 'freshly' delivered afterall! :D

Cheers,
Grid2


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 Post subject: Re: Is my new capacitor within tolerance?
PostPosted: Mar Sun 11, 2018 4:12 pm 
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Location: Hudson, MA
Beautiful Capacitance Bridge, but your calibration sticker expired 50 years ago :shock: :)

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 Post subject: Re: Is my new capacitor within tolerance?
PostPosted: Mar Mon 12, 2018 2:00 am 
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Joined: Jun Sun 14, 2009 10:44 pm
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Eddy wrote:
but your calibration sticker expired 50 years ago :shock: :)

Attachment:
CalibrationSticker_1968.jpg
CalibrationSticker_1968.jpg [ 24.3 KiB | Viewed 176 times ]


True - though the good news is that if you were able to pick that out your eyes are in calibration !!

Cheers,
Grid2


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