> I just looked up "Vactrol" and realized that resistance is inversely
> related to LED current.
>
> What are you trying to accomplish? Schematic?
>
> ...Jim Thompson
I wish to use the Vactrol to replace an RTD on a existing system. I wish to simulate the RTD so the system will think it still read temperature, while it will be a value set by my equipment. I need something completely isolated, it's why the Vactrol appear to be a acceptable way to go.
I can use it has is, but I have really not much resolution in the value of resistor require. The circuit is simple, the D/A output drive a transistor as buffer that drive the Vactrol LED via a simple resistor. I can set the D/A output from 0 to 5 Vdc, the resistor as been select for 40ma on the LED at 5Vdc. The Vactrol LED need 40ma for minimum resistor output.
So my hope is to find a way to build a simple circuit that can will reverse the curve of the LED and end up with something more linear. This should give me a better resolution in the range I need.
Bye Jacques