On Mar 17, 10:13 am, jb-electronics <webmas...@jb-electronics.de> wrote:
> Gaston, thanks for your view as well, but I think I don't really get it. > Even if the LED is not linear, so what? The current meter should still > show the correct value, right? I mean, I cannot adjust it in any other > way than turning one trim pot. So if it shows the correct value for one > setup, it should also show the correct value for all others. > > So the only reasonable thing to do is to calibrate it at a higher > voltage as I understand it, right. > Jens, what I tried to say is: The current through the network is a function of the total voltage and the total resistance (Ohm's law) Roughly: - The voltage is the one of the power supply less the LED voltage drop. The LED voltage drop is a function of the current that passes through it. - The resistance is the sum of your trimpot's plus the two ammeters in series. If this are comparable to the trimpot's then we start to have a problem. And the real problem is that finally the current is a function of the voltage and... due to the LED, of the current itself !!! Thus to eliminate sources of errors: - get the trimpot as high as you can (thus to keep the current in check, means increasing both voltage and trimpot's value). This is to (coarsely) simulate a current source. - get rid of that LED!!! Regards Gaston -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
