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Unread 05-01-2011, 13:36
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Re: Jaguar current sensing technical details?

The INA193AID has a gain of 20V/V, with a typical output error of +-0.75%.
The full-scale input voltage is 150mV. That means it can detect up to 150A, if the resistor could handle it. 150A * 0.0075 = 1.13A. In other words, they should have used a larger resistor. Say, a 3 miliOhm resistor would cap off the measurement at 50A, and create only 0.38 A of error once amplified.
(Also note that the maximum error is 2.2%)

With that information, I would blame most of the inaccuracy of the current measurements with the Jaguar on the op-amp.
However, it might be good to look at the accuracy of the resistor as well. I wouldn't be surprised if these Jaguars have no factory-calibration.


Here's the schematic for the Tan Jaguar:

Apparently it's just on the low side of the gate driver, with a 0.5 miliOhm resistor, so it only senses the current of the motors, not the device itself.
The FAN4174IP5X seems to function purely as a buffer; it does not appear to amplify.

I've attached datasheets for the INA193AID and the FAN4174IP5X.
Attached Files
File Type: pdf INA193AID.pdf (224.3 KB, 13 views)
File Type: pdf FAN4174IP5X.pdf (1.07 MB, 9 views)
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Last edited by kamocat : 05-01-2011 at 14:46. Reason: correcting misinformation
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