using 4060 pci and extended range resistace

[driller45]

ive been using the 4060 pci to log the resistance rise and fall times in photo resistors.

unfortunatly i need to use the recomended 1 meg resistor in parralel to log resistances of

over 500 meg ohm .

ive been using lab view 8 and some of the provided VI examples for this process,

the problem is that none of the scales give me an accurate reading when i use the 'dropping'

resistor.

the manual or brochure says ' extended range' with 1 meg resistor.

how do i configure or approach this problem ?

the readings for something in the 500 meg ohm range

only register as 1 meg plus a few small digits.

i couldnt find any posts on extended range resistance

or a formula to decipher the readings.

thanks for any help

gregory

[Abhinav T]

Gregory,

Thankyou for posting to the National Instruments Forums.

The extended range mode uses a very small current to measure the resistance and thus requires that you use sheilding around not only the cables to the resistor but the resistor itself needs to be shielded in a metallic box.

Also, you will need to perform post processing on the resistance measurement (according to the formula in the attached picture). Please refer to this knowledge base for more details.

Hope this helps!