IV converter circuit for solar radiaiton meter

[Jellie7r]

hi!
i am a newbie and am designing a solar radiation meter using PIC 16F876. Using a small solar cell array, i am suppose to measure its current in terms of voltage. therfore i need a current to voltage amplifier which then will connect to a data amplifier (consisting of 4 op amps in total).

I know the how the rough circuit is like but i am not sure how the actual cirucit will be. Have not deal with such multistage op amp before. The output voltage should have a max of 5V only (to be measured by the PIC after an AD conversion. Any help please?

Thanx!

 

[Nigel Goodwin]

To measure current you simply measure the voltage drop across a resistor in series with the load. In order to minimise losses, this resistor would normally be a low value (depending on the current involved), and you would use an opamp to amplify the voltage to a suitable level to feed the A2D in the PIC.

For an example, a 1 ohm resistor would drop 1V at 1A, and you would need a gain of 5 to give your 5V maximum reading for the PIC. However, 1V is probably far too much to lose, so using a 0.1 ohm resistor and a gain of 50 would only lose 100mV. The maths involved is pretty simple!.

If your opamp and PIC circuit is seperately powered, this makes things a LOT easier, if it's a common power source things get more complicated!.

You might have a look at my analogue tutorial, which could be easily extended to do what you want!.

One thing you haven't mentioned is your load?, a great deal will depend upon that!.