Phil said:
Looks useful in principle but (unless I miss my guess) not so useful in
practice. The major problem I see is the dip switches--typically these
aren't designed for repetitive use, so I'd worry that they'd become flaky
quite rapidly.
Those DIP switches are SPST, I gather, so all your Rs and Cs are wired in
series, with a DIP switch in shunt with each one. This makes the flakiness
problem significantly worse, since instead of 2 contacts (for a rotary DPNT
wafer switch) you've got N contacts in series.
They are rated for 10,000 actuations. We thought about using a rotary,
but felt that the ease of replacement was more important. My experience
is that most decade boxes get damaged by inductive loads or overcurrent
long before the switches wear out.
Capacitor tolerance is another issue--those are mostly ceramic discs. What
capacitance tolerance and tempco are they?
The first 100 we made have 7.5% cheap capacitors, but we may change that.
Also, we expect that most users will be willing to solder in different
parts if they don't like the ones we picked.
And what about the inductance and capacitance of all those traces?
That's a generic problem with any decade box. If inductance and
capacitance matter to you, you really shouldn't be using a decade
box.
Come to think about it, I really should characterize these specs.
If someone here is willing to measure the residual R, C, L and the
-3DB point, I will send you one and you can keep it.
