Are these capacitors dead?

[Legion]

I went to a local electronics surplus store today and picked up a random assortment of components. Some of the capacitors I bought don't seem to work and I can't figure out how to read their markings. Google searches for the markings didn't yield any useful results.

I bought 4 ceramic caps with markings reading WDC 68J N470. I can't get a capacitance reading out of any of the 4 with my DMM. Same thing with another set of 4 ceramic caps, these one's marked 5% 47 N750. All the other caps I bought read fine on the DMM. I'd expect the odd component to be bad, but the fact that all 4 don't seem to work in both cases makes me wonder if I'm doing something wrong.

So is there something else I should try? Should I toss them? Any idea what the capacitances of these are from the markings?

[mariush]

Your multimeter is probably not sensitive enough to measure such low capacitance or maybe the capacitors are faulty (open)

If they're really capacitors, one of the numbers is capacitance, the other is voltage. Could be 68 pF 470v  and 47 pF 750v rated capacitors.  But 470v and 750v are really big numbers, kind of hard to believe it.

It could be that the numbers are written using the convention that the last digit represents the number of zeroes so then 470 becomes 47 x 10^0 = 47x1 = 47  and 750 becomes 75 x 10^0 = 75v.... but it's just a guess.

The J says tolerance +/-5% .. see http://wiki.xtronics.com/index.php/Capacitor_Codes , table 2.

edited to say picoFarads (pF), not nanoFarads (nF).

[Monkeh]

N470 and N750 could be temperature coefficients.

Most likely your meter isn't sensitive enough.

[PA0PBZ]

I think these are 68 and 47 pF capacitors. The number after the N represents a Negative temperature coefficient, although 470 is a bit weird, it's normally something like 500, 750 and such.

[Monkeh]

I think these are 68 and 47 pF capacitors. The number after the N represents a Negative temperature coefficient, although 470 is a bit weird, it's normally something like 500, 750 and such.

470 is normal, just like 47.

[Legion]

Yeah, they  might be below my meter's sensitivity if they're 47pf and 68pf. The lowest mine goes is 100pF. It's an Agilent U1242B.

[fluxcapacitor]

N470 and N750 could be temperature coefficients.

Most likely your meter isn't sensitive enough.

Theres a chart on wikipedia that says they are temperature coefficients.Also the J is 5% tollerance rating.It doesnt mention anything about WDC but thats probably the series or manufacturer .

http://en.wikipedia.org/wiki/Ceramic_capacitor

Class 1-ceramic capacitors
Ceramic names, temperature coefficients ?, ? tolerances and letter codes for ?
referring to IEC/EN 60384-8/21 and EIA-RS-198