Adjustable Capacitance decade box 10p - 1u

[Diabolical Artificer]

How would you go about building such a box with a resolution of say 10p? I've tried working it out but got in a mess, also looked online for possible schematics.

Any idea's, Andy.

[Refugee]

The challenge with decade boxes is the compromise between screening and pickup of external signals.
I looked into the same problem for adding capacitance ranges to an AC resistance bridge but came across a full blown LCR bridge while looking for a decade box or parts to make one.

[Ed_Dinning]

Special switches are available for this use to minimise the caps required. They switch in a sequence of 1,2,4,8 or 1,2,2,4 and others.
Getting a low value of stray capacitance will prove difficult

Ed

[ppppenguin]

I have a capacitance decade box. 100pF to 9.9999uF.  Haven't used it for years. £20+postage.

As others have said, getting below 100pF without strays becoming significant is difficult.

[Diabolical Artificer]

Thanks chaps. Jeffrey's box looks an easier prospect than building one, PM sent.

Andy.

[ppppenguin]

Decade box now on its way to Andy.