I was measuring a 10pF 0603 +-5% (Johanson 251R14S100JV4S) using a network analyzer at 319.5MHz. The cap came in their high q/low ESR ceramic kit.

It measured about 10.7pF. But after measuring a few more 10pF parts, I noticed the capacitance was either around 10.7pF, or 11.3pF, give or take .05pF. Even after checking a dozen or so, they were all grouped around 10.7 or 11.3. In other words, NONE were 10.9 or 11.1.

Any idea why? I know the nominal capacitance is different at frequencies other than their test frequency, but I guess I expected them all to center around some value and be randomly sprinkled within 5%.

  • \$\begingroup\$ Did you calibrate your NA and fixture properly with no cap?? then with 50R. . . . It looks like your fixture is 1pF. I would expect batches to be very consistent and you have samples from 2 batches. \$\endgroup\$ – Sunnyskyguy EE75 Jan 11 '17 at 23:11
  • \$\begingroup\$ I calibrate the NA each time to 50R. My test "fixture" is a piece of coax cut to the same length as my calibration standards, and I get almost exactly 0Ω and ∞Ω with the fixture. I assumed they had included caps from two different batches in the kit, but wanted to make sure someone else had seen that before. \$\endgroup\$ – Lance Beasley Jan 12 '17 at 11:55
  • \$\begingroup\$ It is possible that the capacitors within 1% or 2% have been binned and sold as such? \$\endgroup\$ – Jameson Apr 25 at 22:51
  • \$\begingroup\$ Regarding the capacitance being out of the +/-5% tolerance (>10.5pF), it may have to do with they way Johanson specs them: it seems like the nominal capacitance is for f=1MHz; as far as the two two clusters of values, most likely they mixed components from two different reels in your kit. \$\endgroup\$ – joribama Apr 26 at 1:01

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