LDR associated with 6008-DAQ problem

Thread Starter

MohammedHA

Joined Apr 20, 2016
2
Hello,
while doing an experiment of measuring light intensity using LDR with DAQ, +5v is connected with 100k ohm resistance and LDR is connected in series to the ground, the output is taken between these two resistors to an analog input pin(voltage divider).
i make labview program to read the signal that comes from the LDR.
the problem was that it gives 100hz noise signal always. i dont know the reason of why this happening.
so, why do i get noise in the LDR signal at 100hz ?
and how do i get rid of it ?

thanks
 

#12

Joined Nov 30, 2010
18,210
The 100 Hz is coming from your power line frequency. Add a capacitor in parallel with the LDR. About 0.1 uf should do the trick.
 

Thread Starter

MohammedHA

Joined Apr 20, 2016
2
The 100 Hz is coming from your power line frequency. Add a capacitor in parallel with the LDR. About 0.1 uf should do the trick.
thanks for response.
But, is there any other (non electronic neither programming) solution as it had been requested from me ??
thanks again.
 

#12

Joined Nov 30, 2010
18,210
i make labview program to read the signal that comes from the LDR.
the problem was that it gives 100hz noise signal always.
Stop instructing Labview to inject 100 Hz noise?
In the real world, you can either add a 10 cent capacitor or build the circuit inside a grounded metal box to avoid outside electrical fields and magnetic fields.
Another way would be to design the circuit with lower impedance, but that is an electronic method which you said you do not want.
 
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