current source measurements

[Martin Czech]

It would be a nice thing if one would be able to measure expo current
sources allone, because this would allow to decide if e.g. the osc. error
comes from osc. delays or current source errors.

The idea is: use a very big MKT or other foil type cap , say 10uF in
an saw osc. arrangement. measure the charge time only (not the discharge time,
the discharge doesn't need to be fast at all this way).

If Imax is 1mA and dU is 10V => t=0.1 sec.
This time is long enough to measure precisely with a quartz counter,
it is maybe even too long.

There was an elektor (?) proposal long time ago where a cap measurement
box was discussed, using precision R for the current an a counter
for time measurement. This seemed to work.`


Any comments ?

m.c.