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Constant Current Supply / Frequence Counter


Hi folks,

I'm looking for a constant current supply ( 1 nA up to approx. 100 mA) and a frequence counter ( up to approx. 1,5 GHz).

The Keithley current sources Dave is using, are at the moment not available. Newer instruments from Keithley are
unbelievable expensive...

Used frequency counters are rare to get. And if there is one e.g. in the USA, the shipping cost are much higher tah 100 US $.

Can anybody please give me some advices?

Tanks in advance!


Ronald / Germany

1nA is a bit tough.

You can look for older HP 61** sources (6177C - 500mA, 6181C - 250mA, 6186C - 100mA).

In the past, I had seen a few on the local ad sites (France) going for some ~100 euros.

I'd split the CC supply into two: sub-10mA and 10mA-5A or so. The design techniques for those ranges are somewhat different and I suspect you'll find it a real pain in the ass to combine them.

I may have some frequency counters coming, but won't know until tomorrow evening, and won't know if they work for another couple of weeks.

You should look at ebay.

Keithley 225:

Frequency counters:


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