Current sensing for speaker life test

[jarjarvai]

Hi All ,

I am planning on using the USB-6225 for purposes of speaker life testing. My connection diagram is as follows: 

What values of R_sense and R_Bias should I use? Also, not shown in the connection diagram but I will be connecting the 6225 through the BNC 2090A box. Many thanks!

--Raj

[Bcortes · Accepted solution]

Hi colleague 

To Answer your question I recommend the following documentation:

Measuring Current with an Analog Voltage Input

Particularly for the shunt resistor (R_sense), I would like to paraphrase the following:

"When measuring current in this fashion, the smallest value of shunt resistor compared to the load resistance should be used. This will create the smallest interference with the existing circuit. However, smaller resistances create smaller voltage drops, so a compromise between resolution and circuit interference must be made."

In this way, the resistance of R_sense should be determined considering the load resistance.

For the pull-down resistors  (R_bias), a high impedance value like 10K would be enough, this because what we want is to pull down the signal when the current consumed by the load is 0A and when it is higher we do not want the pull-down resistors to interfere.