Need MA to voltage converter help

Oct 09, 2008 5 Replies

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Jim 17 years ago

I have a sunlight sensor made up of 2 tiny amorphous solar cells in parallel, that I would like to use with a 0-5 volt data logger. These cells provide the spectral response I want.

The cells together generate a maximum of 2.25ma of current in full sunlight that I need to convert to voltage.

I have used a OP90 op amp in the past to do the same for other sensors, but only for microamp currents. I did the math to find the value of the feedback resistor for this, and come up with something like .0022 ohms which doesn't seem too workable. Either I am making a mistake in my math or maybe it isn't possible to do this conversion using a single op amp.

Can someone give me an option for making this a>v converter for this 2.25ma current?

Thanks Jim

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Tom Bruhns 17 years ago

cells

ich

maybe

Not sure how you came up with that resistance value, but I'd suggest you revisit your calculation. When I do it, I get 5V/.00225A =3D 2.22k ohms, not a bad value at all. Looks like you lost 6 orders of magnitude somewhere.

(It's always good to double-check your answers, especially in cases like this where the result seems odd. For example, 2.25mA times .0022 ohms is 5 microvolts, not 5 volts. In other words, plug your result back in to do the checking so you're lest apt to make the same mistake over again.)

Cheers, Tom

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Jim Thompson 17 years ago

Maybe MA means Mega-Amps ?:-)

...Jim Thompson

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Tom Bruhns 17 years ago

On Oct 9, 5:03=A0pm, Jim Thompson wrote: ...

Just solved the world's energy crunch, if so! ;-)

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John Fields 17 years ago

View in Courier: +--[2K2]--+ | | +----+-|-\\ | |- | >----+-->Vout [PV] +-|+/ | | +----+------------>GND | GND JF

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Rich Grise 17 years ago

When I first read the OP, I misread it as nanoamps. ;-)

Cheers! Rich

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