Reading Capacitor Values...

[lord loh.]

I am sorry and embarrassed to ask such a basic question after being an "Electronics Expert".

How does one read the value of disk capacitors...

I have been to Tony van Roon's site and have read the capacitor tutorial there but a few doubts still remain as what my teacher at school told me does not exactly match.

What my teacher said was, if there is a line below the value, the units is picoFarads.
ex: 104 and a line under it is 10x10^4=100000pF=100nF.

Tony van Roon's site says that if the value is written as decimals, it is microFarads.
ex: .001=.001microFarads=1nF.

But I have seen capacitors that have values like 68 and 22 written on them. There is no line under them. How do I read these as? Could the explanation of my teacher be wrong? (They are known to make mistakes...) :?

 

[Nigel Goodwin]

I am sorry and embarrassed to ask such a basic question after being an "Electronics Expert".

How does one read the value of disk capacitors...

I have been to Tony van Roon's site and have read the capacitor tutorial there but a few doubts still remain as what my teacher at school told me does not exactly match.

What my teacher said was, if there is a line below the value, the units is picoFarads.
ex: 104 and a line under it is 10x10^4=100000pF=100nF.

Tony van Roon's site says that if the value is written as decimals, it is microFarads.
ex: .001=.001microFarads=1nF.

But I have seen capacitors that have values like 68 and 22 written on them. There is no line under them. How do I read these as? Could the explanation of my teacher be wrong? (They are known to make mistakes...) :?

68 and 22 will be in Picofarads, as Tony van Roon's site says, if it's got a decimal point it's likely to be microfarads, if not it's likely to be picofarads.

I wouldn't say that all picofarad marked capacitors are underlined, it 'may' be that only those with abbreviated values are (104 instead of 100,000), but not all those are underlined either!.

 

[jrz126]

I can never really remember the conversions, so I just use this pic to figure it out...

 

[lord loh.]

Now here are a few capacitors....

1. A capacitor marked 220 with a line under it. And the words "AEC" written below it. As Nigel said, this is supposed to be abbreviated, and should mean 220 picoFarads. They might have as well not bothered about the line and let the capacitor say 220 and mean 220 picoFarads.

2. A capacitor marked 2.2 with a line under it. I guess it is 2.2 picoFarads.

3. A capacitor marked 4.7 without a line under it.

How do I read these three capacitors?

And as per jrz126's image there is nothing for capacitors of 0.22 pF.... I remember seeing it in the shop. Or am I mistaken?

 

[Nigel Goodwin]

Now here are a few capacitors....

1. A capacitor marked 220 with a line under it. And the words "AEC" written below it. As Nigel said, this is supposed to be abbreviated, and should mean 220 picoFarads. They might have as well not bothered about the line and let the capacitor say 220 and mean 220 picoFarads.

2. A capacitor marked 2.2 with a line under it. I guess it is 2.2 picoFarads.

3. A capacitor marked 4.7 without a line under it.

How do I read these three capacitors?

And as per jrz126's image there is nothing for capacitors of 0.22 pF.... I remember seeing it in the shop. Or am I mistaken?

All those values are pretty obvious, and you don't get 0.22pF capacitors, it's really too low.

 

[lord loh.]

All those values are pretty obvious, and you don't get 0.22pF capacitors, it's really too low.

:cry: :cry: :cry: :cry:

I am not able to comprehend them....

if a capacitor is marked 220 with a line, it should be 220pF.
if a capacitor is marked 220 without a line, it should be 220pF as well.

As I know, the first two digits of the capacitor is meant for the first and second digit. And the third digit, if it exsists, is the multiplier(10 to the power of third digit).

So my guess is 2.2 with a line is 2.2x10^0=2.2 pF? okay.... I understand this as I write...Sorry....

But what is the point of the line below the 2.2? Would it not mean the same without the line?

 

[Nigel Goodwin]

I don't see any relevence in a line or not?.

 

[audioguru]

A capacitance of only 0.22pF would be made from the toes of a small ant.
Two pins from a DIP IC have about 5pF between them.

Philips used to write "n47" on their 470pF caps. I guess they never went to the orient. Yes, I have some of those caps with the numbers written by hand! :lol:

 

[Nigel Goodwin]

Philips used to write "n47" on their 470pF caps. I guess they never went to the orient.

That's quite simple as well, 0.47nF - which is, as you quite rightly say, 470pF - however, their way only takes three letters, rather than five 8)

It's a common way of labelling, likewise "u47" would be 0.47uF, or 470nF, or 470,000pF to be pedantic :twisted: