Possible to measure cable capacitance reliably at home with a Capacitance meter?

If one had a "good" Capacitance Tester / Meter at home, can they then reliably measure the capacitance of their RCA, Coax and other cables?

If so, what is the what is the correct process for measuring said capacitance, an what is the formula one would use to account for the different lengths of the cables? Is there any accounting in measurement for 75 ohm connectors?

Finally, the word "good" is in quotes in the first sentence - what would one have to spend for a "good" capacitance tester? $50? $100? More? Less?

 

At one time I was making a few cables and I did buy a capacitance meter. I think it was about $70. I don't know how accurate it is. I remember many years ago testing capacitance with a signal generator and a LCR bridge and doing the calculations, and I suppose the only way to satisfy yourself that the $70 capacitance meter is doing the job is to make some measurements on both systems and compare.

Nevertheless, I had fun with my meter. As you might guess, the capacitance of the wire itself can be very low (depending on the design) but the connectors add quite a lot. I found that the Bullet RCA plugs had the lowest capacitance of the ones I tested.

 

50 dollars would be fine.
I bought one on EBay brand new.
Select a pf setting Higher than required
And connect red to centre conductor.
Black to outer.and capitance is read.
Same for capacitors .
Remove leads from phono cartridge( unless your headshell is removable,
To measure tonearm capitance.
This little device has brought "Law and
Order "to my system.

 

Thanks guys!

Question - is it true that a capacitance meter, although perfect for a capacitor measurement, will not give an accurate reading on a cable unless you account for the length of the cable somehow? What formula do you use, if any, to account for varying cable length when measuring capacitance??

 

I did not know that. Do you have a reference?

 

I don't think this is true. I cut down my phono cables to 1/3 of original length to reduce cap and the measurement went from 100pF to 33pF. My meter is inexpensive, but it is accurate when I test against published specs.

 

That's why I am asking - if you look on the net, it is implied in many threads, but having trouble getting the concrete formula.

That is why I started the thread and asking, there are folks here who know way more than I do about this. Maybe it doesn't - like you I don't know.

My little reptilian brain is telling me that the cable length does "matter" though (yeah, keep it clean guys).

 

If that said "I am 100% certain" I would not have quoted it! Are you certain?

Every time I think it is not true, I read something that says it is, the net is loaded with threads saying that your calcs have to account for cable length if you use a handheld meter. BUT I DON'T KNOW, not saying you are wrong, just trying to get 100% certainty so the information here does not mislead anyone in the future.

 

Well, just surprised to hear this. The cable I'm talking about, if you contact the maker, will tell you it is a 100pF cable. I measure it with a meter and indeed that's what it is. I cut 2/3rds of the cable off, reterminate, and then remeasure the the cable and it is 33pF (actually the meter reads 32pF). I've measured other cables and found the pF/foot at stated worked out with measurement and simple math. I certainly could be wrong, and there may be additional influences over very long runs, but…

 

Not sure what happened there. Did i interfere with someone's entry .
Anyway. I know of no formula for cable length.
If i measure a meter of interconnect
And then
Measure 1/2 of a meter then the reading will be lower.

 

Thanks. Of course, just trying to sort out the myriad of responses I have read and sort out the facts... these days the internet can give as much misinformation than information.... I don't want my threads to be the same!!

Do you think the measurements with a sub $100 capacitance meter are reliable enough for weekend warriors like me? Again, different opinions, some contend that true capacitance measurements require expensive testing equipment? Or in your opinion are we getting to the 90% confidence level with these sub $100 capacitance meters?

EDIT: I should qualify the question in the second paragraph with "when measuring longer cables, say over 6 ft in length". For capacitors, I know the meters are good... just wondering % error on cables, especially as length increases.

 

I have not gone into it in depth.
My calculations for the Shure V15mk3
At 450pF provide the best sound
Quality, so it seems accurate.
When i measure capacitors its deadly
Accurate.

 

Typical capacitance measurements are reported per foot or per meter by wire and cable makers. Capacitance is cumulative. Therefore, not including connectors at each end, you have to multiply the capacitance per foot by the length of the cable you want to use in order to determine its capacitance. Measuring the capacitance of connecteors is problematic, but because they contribute only a very small amount of capacitance in a typical audio external wiring configuration, using a default number is safe. Check the connector maker’s web site for nominal ratings. Generally, except for very low voltage circuits (e.g., cartridge/tonearm wiring) the connectors are almost inconsequential.

For commercially available audio speaker cable for example, you’ll find capacitance rating that range from a few pF per foot up to 50 or more pF per foot. In general for typical commercial speaker cable wire configurations, higher capacitance indicates lower inductance which is a design decision on the part of the wire and cable maker consulting together on a particular cable design.

A typical meter available for $75-$125 is likely to be accurate (depending on the model and cost) down to +/- 0.1 pF, so it’s far more accurate than actually needed for audio cable measurement use. The specs for any particular meter will list its accuracy range for each mode.

Resistance measurements (usually stated in ohms) are typically quoted for wire and finished speaker cable as either ohms/100 meters, or ohms/kilometer. Good, finished speaker cable typically runs 0.01 ohms or less per 100 meters (330 feet). Vanishingly low, in other words. A typical ohm meter or general purpose multimeter available for $25-$45 in hardware stores or online, is usually accurate down to +/- 0.001 ohms, which again is far more accurate than actually needed for audio cable measurement use.

 

Not my experience at all.

 

I just haven’t found that connectors add or subtract much. The electrical differences are measurable, no doubt, for speaker connectors (i.e., bananas and spades). But they don’t add anything significant enough to trouble or help even an entry level amp, IME.

 

Bananas and spades? I was referring to interconnects

 

Uh-huh. I was relating my experience actually doing cable measurements. Most of that has been speaker cable, both raw wire and finished cables. The experience directly applies to interconnect wire and to RCA connectors. As with bananas and spades, IME, different types of RCA connectors have some noticeable variance, but not enough to be any sort of significant factor except when doing calculations for phono cables.

 

I ended up buying this Amprobe AM-510 Multimeter | Compact and Durable and it works fine. I verified the capacitance readings against certain known values on manufacturer cable sites, and it reads fine.

I had a Fluke and cheap Innova Multimeter and none of them had capacitance settings, so bought another. I chose a multimeter because of the wide range of use, and this one turned out to be pretty good, I will replace the cheapo Innova I have.

Thanks all for the help on this... it turned out to be as simple as everyone stated.

 

One more thing worth noting - the Amprobe 510, like most Multimeters that measure capacitance, only has a resolution down to 10's of picofarads (pf) - which means you multiply by 10 to get your answer. It also means that you cannot resolve down to 1 pf - so if you were measuring a 1 ft BJC LC-1 for instance - it would read "1" that means your answer is anywhere between 5 and 15....

For most purposes, this resolution is fine... especially for most cables, especially considering most cables are more than a foot.

All that being said, I am thinking of getting this instead - https://www.amazon.com/gp/product/B0002HDTDQ/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1 which looks suspiciously like this for $40 more - https://www.amazon.com/gp/product/B...2b1-5e49-9367-ec871c9436c5&pf_rd_i=5011682011 just a different color. Probably made in the same factory.

I know the B&K is good - in fact I think I had one a few years back. I suspect the Ellenco is the same meter....

 

I have a cheap dedicated cap meter. Nothing to compare it to. It has a calibration situation, where you can zero it out.

 

The B&K 810C I linked to above - considered a good capacitance meter - in fact, I saw in another thread somewhere that Metralla (one of the posters above) has the B&K - but I think he has older model 810B. It has been around a long time, and reviews well. Almost overkill for what we are doing - but good nonetheless. It's $80-ish.

As I stated, the Ellenco I just bought appears to be the B&K, just $40 cheaper. (probably made in the same Taiwanese factory).

This one also reviews well, but was one level below where I wanted to go. https://www.amazon.com/gp/product/B009CSR8BA/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=A20H555M9MROEP

 

I was reading the thread chronologically and when I saw "B&K" I thought - hey, that sounds familiar. I just checked the cupboard. Yep, B&K Precision 810B. I had totally forgotten what model I had. $80 does sound right. Good tools last a lifetime.

 

Honest, I wasn't digging around in your cupboard!!