Quote:
Originally Posted by mcudogs
Paul, the LEM300 output is from an op amp that is fed from the +5vdc supply on the control board.
|
The schematic confused me for a while too until I looked up the part number - the triangle-looking U8 is a comparator, not an opamp. I think that this comparator triggers the hardware overcurrent when the LEM output rises above a specified voltage.
Paul, another thing to consider - i noticed there isn't an output vs input graph on the LEM datasheet. when i looked at the Tamura brand, they have a graph that shows this and the output is only linear in the rated range (like, 600A for a 600A sensor). After that, the slope decreases - thus, if you're assuming a linear relationship, it'll take more amps than you predict to get to the sensor output voltage required to trigger the overcurrent protection.
However, I don't know if this is also true for the LEM sensors...
here's a link to the tamura datasheet
http://www.mouser.com/catalog/specsheets/L03SXXXD15.pdf
I also notice they're $10 cheaper and the same size - any reason for going with the LEM vs the Tamura? (of course, my tamura also needed +5V and -5V to work, so it'd require more parts).