light intensity measurement in a random space

[Aaashh]

Hey guys, 

I have a question. When measuring the light intensity using a simple circuit with a LDR and a resisitor, connected to a MCCDAQ, the measured value is in Voltage,right? 

But I need the value in lumens. What is the formula from voltage to lumens? 

[Bob_Schor]

Read the documentation that comes with your sensor, the device that takes in light (in some units, perhaps lumens) and outputs voltage.  If there is no such documentation, then learn about calibration, where you provide a known input, measure the sensor output, and derive a formula (perhaps a linear relationship, perhaps a more complex function) that lets you do the conversion.

Bob Schor

[Aaashh]

Thank you very much. 

So I used a 4.6K ohm resistor. 

The formula I found is : 

Lux=( (2500/Vo)-500)/4.6

This is my result. The problem now is that the value is flucuating when i’m measuring in a closed area. Here they are using fluorescent tubes. What can I do to get an average value? 

[RavensFan]

Take multiple readings and average them!  The Mean Pt by Pt function would be useful to you.

Be sure to use block diagram cleanup on your VI so that you don't have backwards running wires and unnecessarily bent and crossed wires which all make the block diagram harder to read.