I've probably asked this before. Not sure if my mind is playing tricks on me, I've got a bunch of ceramic Caps Marked "100".

Is this 10pf or 100pf?  I've always taken "101" to be 100pf (y'know, 10 and 1 zero = 100p) so I'd normally be inclined to assume it would be 10pf, but somethings annoying me at the extra zero. Surely it can't be "ten and zero zeros" and so must be 100pf. But that begs the question, why would 100 and 101 both be the same value? Are capacitor manufacturers deliberately messing with our heads?

'Lil help please!

Cheers
Iain

This would be 10pf. I use a free little program called Electronics Assistant. Good for this type of thing as well as resistor color codes and choosing current limiting resistors. Though, with those, i pretty much know what I'm going to use as far as pedals are concerned. Looks like it does inductance, power, frequency and more.

I would expect a 10pF to be marked "10".

A good enough excuse to buy a quality LCR meter?

Quote from: EBK on March 31, 2020, 04:32:52 PM
I would expect a 10pF to be marked "10".

Same! Just like I'd expect 100pF to be marked 101.

Quote from: bloxstompboxes on March 31, 2020, 04:30:56 PM
This would be 10pf.

Without any doubt?  I've never seen any other sub 100pF cap show three figures.

Quote from: EBK on March 31, 2020, 04:32:52 PM

A good enough excuse to buy a quality LCR meter?

I doubt it, but I have considered it in the past, we'll see how long this conundrum keeps me awake!

You could measure it with your DMM...

Not sure that's possible with my DMM.

I've always known my multimeter was cheap and a bit rubbish (it doesn't even have a continuity "beep" mode) but I'd be surprised to learn y'all are are rocking multimeters that can measure capacitance. Am I really that far behind the times?

> I'd be surprised to learn y'all are are rocking multimeters that can measure capacitance. Am I really that far behind the times?

You and me brother. You and me.

All my life a cap-meter was a special box and rarely worth the price. But really with microelectronics a cap function costs pennies. It makes (part of) the difference between a basic $4.98 DMM and a $5.98 full-feature DMM.

I just looked. My last DMM had Hz and Duty and I thought that was spiffy. My latest does have "uFd". I'm not interested enough to see if it would know 101 from 100 from 10. (It's a Electrician's Meter so probably sorts motor-caps not radio-caps.)

I double checked. Should be right:

OK, I'm not finding with-C DMMs under $10. Here's two. The colors are different but note the model numbers are more alike than different-- these come from the same maker.

Cheers Paul. IIRC I've seen some cheap cap meters on ebay  but it's not something I've considered a necessity. This is likely just cabin fever setting in.

Also, thanks for your reassurance Eric. You'll have to forgive my scepticism. I'm just having one of those moments.  On closer inspection of my parts drawer it's not just 100.  I've even found some 150. I'm just accustomed to this range being labeled  10 for 10pf and 101 for 100pf. Similarly 15 for 15pf and 151 for 150pf. 

I don't need or have any pressing use of these 100 and 150 caps. I just noticed the 100 earlier and it's been really annoying me ever since.

FYI: Not many cheap cap meters, or DMMs with capacitance, will read very well down to pFs, if at all.  You need to do your research.   (Even if it does measure down to pF you will need to subtract off the capacitance from the meter and meter leads.)

I'm not recommending this but there's a few like this around for $20,
https://www.amazon.com/Capacitor-Capacitance-Digital-200pF-20mF-XC6013L/dp/B00NE9J9Y2

Accuracy of 2% on this one is OK for part identification.   There was another one I saw which had an accuracy of 0.5% for a similar price.

All cheap junk but convenient if you need to measure something.

Another thing to consider is most cheaper meters will not measure capacitance accurately, or at all, when measuring in-circuit.   

Some of the better LCR meters will measure in circuit to some degree.

As you crank up the accuracy or quality the price will exceed your budget for sure.

It's not hard to build your own simple C-meter.  LCR is a bit more involved.

I'm using this dmm: https://eboltslovensko.com/listings/multimeter-re64-range-mastech/?page=1
It's the only website I can currently find that states a price.

I bought it 15 or 20 years ago in a local shop for around 15 euros iirc.
It's available under different brands. Mine is yellow btw.

The manual states 4% accuracy for caps.
The pF caps I measure come close to the stated value. But 10pF and 100pF might be on the tricky end of the scale.

Quote from: slashandburn on March 31, 2020, 04:15:04 PM
I've probably asked this before.

Me too, it was my very first post on this forum btw.
This is what PRR replied 6 years ago:

Quote from: PRR on May 17, 2014, 05:52:07 PM
Older ceramic caps just wrote the pFd. "150" is 150pFd.

Newer ones do use the xxd notation, where "d" is a decimal multiplier. So "150" would be 15 times 10^0 or 15pFd.

You can also look at the circuit and ask "does this make sense?". As a general thing, 15pFd is "too small to do much" in audio systems, 150pFd will tame treble in networks with ~~100K impedance.

https://www.diystompboxes.com/smfforum/index.php?topic=107247.msg973540#msg973540

The other replies in that thread are worth a read as well.

QuoteI'm using this dmm: https://eboltslovensko.com/listings/multimeter-re64-range-mastech/?page=1
It's the only website I can currently find that states a price.

I bought it 15 or 20 years ago in a local shop for around 15 euros iirc.

Probably uses this (much copied) circuit.   It's not bad it uses a sine-wave and doesn't totally barf-out when there's parallel resistance.  Also has a 2n range which scrapes in the smaller cap values.



Cap meter is IC4, IC5 but also needs IC2 just above it to convert AC to DC.

You'll probably find you can put resistors (and inductors) across the cap terminals and get measurements which correspond to the part value based on the impedance.

Not meaning to be argumentative here but all this chat about meters to measure capacitance won't help me sleep tonight. Ah, more rum I guess!

Do I take this as a "it's hard to say for sure without measuring it"?

I know I'm not alone in having found some component markings headache-inducing but until about three drinks ago I thought the three digit code for capacitors was somewhat foolproof.

Hopefully this is just the rum talking and it'll all make sense in the morning. I just don't get it though. If 82 is 82pF, and 101 is 100pF, what kind of sick minded person would label a similar component 100? And why?

Quote from: slashandburn on March 31, 2020, 08:17:55 PM
Not meaning to be argumentative here but all this chat about meters to measure capacitance won't help me sleep tonight.

Re-read the last part of my reply.

QuoteHopefully this is just the rum talking and it'll all make sense in the morning. I just don't get it though. If 82 is 82pF, and 101 is 100pF, what kind of sick minded person would label a similar component 100? And why?

Don't feel bad out of all the crappy labeling things that's got to be one of the worst cases of ambiguities.  Peeved me off when I was a kid and still does today!

It's comes from two numbering schemes the common "101" = 100pF and "100" = 10pF vs the literal labeling of "100pF".   In the scheme of "100pF" 100 is the lazy and ambiguous trouble maker.   Now there was one more labeling scheme  when you see 10, 50, 100 with an underline under the number that meant the value was literal  so 10pF,  50pF, 100pF.



You can rig-up circuits to determine the value.   A common one is the oscillation frequency of a 555 timer, which has about 30pF internal capacitance you need to take into account, and might not oscillate with 10pF.

Another is to wire-up this low-pass circuit with 1M resistors for R1 and R2.  If it's 100pF you should hear quite a bit of filtering of the highs whereas if it is 10pF you should barely hear and filtering of highs.


EDIT: added cap pic

Thanks I caught that but didn't read the thread until just now.

I dont have a circuit to give the part any conext, just loose parts in a drawer.

Paul's post suggests that it can vary depending on the part, some parts use 0 as the multiplier, others will just say 100 to show 100pF. Duck_arse in that thread suggests that 100 would surely imply 100pF.

I give up. Its not even all that important, I instinctively reached for the familiar ones marked 101, it just became one of those nagging passing thoughts that managed to grow out of proportion.

Edit: Rob my man!  I love a practical solution that involves no money. Circuit and socket! Shame im not sure I've got the time, patience nor fine tuned ear, especially considering it won't yield a definitive answer. (two numbering schemes? Bollocks to it. Not worth the headache!)

QuotePaul's post suggests that it can vary depending on the part, some parts use 0 as the multiplier, others will just say 100 to show 100pF. Duck_arse in that thread suggests that 100 would surely imply 100pF.

Paul's post agrees with my experience.

I can only add the underline thing.   In my experience, if it *doesn't* have the underline most of the time 100 would be 10pF.   That would be most probably value.

EDIT:
(Duck_arse's thing about the n15 = 150pF is definitely true as well.  I think that was for Philips ceramics which had the smaller squarish packages.)


Sorry about the EDITs.

QuoteEdit: Rob my man!  I love a practical solution that involves no money. Circuit and socket! Shame im not sure I've got the time, patience nor fine tuned ear, especially considering it won't yield a definitive answer. (two numbering schemes? Bollocks to it. Not worth the headache!)

The no money solution:
- set meter to AC
- connect the cap in series with one lead of your multimeter
- then connect the other meter lead and the free end of a cap to an AC transformer

If you measure 12V rms on the transformer directly then you should see about 400mV with a 100pF cap.  That's 1/30th of the direct voltage.  It could possibly be down to 200mV due to the meter's capacitance.  The 10pF will be a lot lower.  That's assuming you meter is 1M ohm input impedance meter.

A 10M input impedance will give higher readings.

Worth a shot.  From the direct measurement and the "with cap" measurement you can get a good idea.

Well  I did the test on a crappy meter and didn't get very convincing results:


Transformer 8V
                                              100pF                  10pF
Meter1 (10M input Z)          1.8V                     0.28V
Meter2  (10M input Z)         1.4V                     0.70V
Meter3  (1M input Z)            0.0V                    0.0V

Meter 3 is an ultra-crappy DMM, the lowest AC range is 200V which isn't enough resolution to see anything at all.