Use your now functioning 4275A to compare ceramic and film cap properties up to 10 MHz.
After looking at the 100nF films caps I have here, I decided to skip them. Their larger package size and hence longer leads puts their self-resonant frequency well below 10MHz, which is not desirable in this situation.
I modified one of my programs for another HP LCR meter to control the 4275A via GPIB. Wrote routines so it measures C/ESR from either Z/phase or R/X data (the latter is preferable, it bypasses all of the 4275A's range limitations), and plots the results.
This compare is of two different 100nF ceramic formulations. The X7R is the 100nF blue chiclets used throughout the 4275A, both for PS bypassing and DC blocking. The Y5S is a 100nF Murata disc that I got a few years ago. After getting some and seeing how good they measured (up to 100kHz back then), I bought a few hundred to have around.
If you want to make yourself sick, put the X7R in the bridge and watch the capacitance and DF change with time. At 100kHz with 1 VAC drive, it took nearly a minute for the value to settle. Change the frequency and watch it migrate again for half a minute. Then add some DC bias and watch the C go down and ESR go up. After this you won't put an X7R in an analog signal path ever again.
The Y5S was much better, settling to final value in <10sec, and showing very little change with freq change or DC.
This test was made after I had already replaced all of the blue X7R's on all analog boards with the Y5S's (except those used for PS decoupling). It was made with conditions similar to what they see in the instrument in the decoupling role: 1 VAC test level with 5V DC bias.
As you can see, the ESR of the X7R is
much worse than the Y5S across the board, by a factor of 10 at 400kHz and worsening below that.
I had to go thru some of the cal procedures again after changing them.
It may be all in my head, but the instrument readings seem more stable, drift less, with the new caps in.
Next I want to take a close look at the calibration steps ( all two of them) that require the standard resistors and capacitors. They are used to calibrate the range resistors.