The inside and “schematic”
I made this at first as a substitution box. Handy while testing prototypes or things like filters. But while measuring the capacitors I decided to make a decade with 1nF, 10nF and 100 upto 1000nF in 100 nF steps. I used foil caps with a low dissipation factor. Most of them are stacked 100 nF.
The cable is shielded per wire and the shield is connected to a guard connection. This way the cabled adds less as 1 pF. The BNC’s are there for use with a vna or bridgemeasurements
After building I measured the values on my GR-1620, values in nF, the second number is DF:
1) 99,819 0,003716
2) 199,512 0,003880
3) 299,970 0,004122
4) 400,753 0,004003
5) 501,145 0,004294
6) 601,824 0,000810
7) 700,193 0,004263
8) 803,256 0,004272
9) 900,631 0,004268
0) 998,734 0,004026
-) 1,01132 0,005613
-) 10,0154 0,005560
With this data it is also a handy tool to check a LCR meter.
The first test.