Hello Everyone,

I almost know nothing about circuit designing, apart from undergrad electronics. For the instrument I am designing
for Radiation Dosimetry application, I have to be able to detect light
with photo diode generating ~ 10pA to 100nA. Currently I am using Keithley
Multimeter. But my system has to be handheld. Could you please give me a
guideline how do I design a circuit to be able to detect this current range?
Any help will be highly appreciated.

 

Hello,

Perhaps the circuits in the following PDF might give you an idea:
Photodiodes: applications

Bertus

 

First, I think this should not be in Programmers corner, because it wont´t get too much attention here.

Second, look at Dave´s uCurrent and see if you could adapt that schematic.
http://www.eevblog.com/projects/ucurrent/

 

Hello Everyone,

I almost know nothing about circuit designing

currents in this range are problematic to measure, because common EMI will induce such currents. Good shielding is essential.

Radiation detector based on photodiodes are possible and have been built, however they have noise problem vs. sensitivity.

Also these don't use small standard photodiodes, but special, large PIN diodes.

 

This should be my field of work but I would have to dig into the books to make it work.
Usually we would use a PMT. Any particular reason for using a photodiode, apart from portability?

 

Thanks everyone for suggestions.
I would use PMT but HV required by PMT is a problem
for portability, and in the wavelength range 750nm, PMT sensitivity
falls rapidly. Infact for testing in the lab I used PMT, PD, CCD...but PD seems to be most user friendly for people and the cheapest.
I contacted with TI, but they also suggested about forums.
So kind of struggling to start with.

 

Hello,

Perhaps the circuits in the following PDF might give you an idea:
Photodiodes: applications

Bertus

The link was lost.
There are two new link here:

Application circuit examples of Si photodiode

Application circuit examples of Si photodiode