Having like many of us a few Led diodes of all kinds and sources, I set out to build an instrument that would allow me to better identify them.
My most faithful review Elektor has proposed in its issue of July 2010 ( n ° 385/386 page 107 ) a very interesting little article on this subject.
The diagram uses two operational amplifiers as well as two conventional NPN transistors, each of the two groups thus designed forming two voltage-current converters.

I have always wanted to equip my lab with a device to measure the values ​​of various chokes. The cost of such equipment was previously quite prohibitive, and so I still do not have any. First of all, know that this small device can obviously not compete with the more complex measuring devices of the trade, it is only a modest indicator allowing to get rid of the value of an unknown self, quite simply. .

What interest will you tell me?
What can it be used for?

The answer is very simple, well ... maybe not that much in the end ...
If your generator is equipped with an input[ VCF ¹ ], then you will be able to control it very finely, for example using a microcontroller system equipped with a DAC converter ( D igtal A nalogic C onverter), clearly a digital / analog converter.
It goes without saying that if your GBF does not have this VCF input, then this accessory will be of no use to you!