INA282 Current Shunt Monitor - Page 1
Forum section: electronics / projects

author: scott216
author_rank: Regular Contributor
timestamp: May 16, 2015, 11:43:25 pm
content: I've got anINA282current shunt monitor and the output is pretty erratic. It monitors the volts across a shunt and outputs 50x this shunt voltage. As a test I've got one hooked up to my bench power supply. I'm supplying 5 volts to the power pins and 0.064 volts to the shunt input pins (1 & 8 ). I've got nice stable inputs, but the output looks lousy. I have the two Ref pins tied to ground and I've got a 0.1uF cap between ground and V+. Attached is a screenshot from my scope. Anybody have experience with this device? Maybe I'm using it wrong.

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 17, 2015, 02:07:44 am
content: You might try putting a load on the output. A 10k resistor, for example.

author: scott216
author_rank: Regular Contributor
timestamp: May 17, 2015, 02:57:31 am
content: Quote from: TerminalJack505 on May 17, 2015, 02:07:44 amI just tried that, it didn't help.

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 17, 2015, 03:36:12 am
content: Do the 0.064V and 5V sources have the same ground? Maybe the 0.064V isn't within the part's common mode range.

author: scott216
author_rank: Regular Contributor
timestamp: May 17, 2015, 02:08:02 pm
content: Quote from: TerminalJack505 on May 17, 2015, 03:36:12 amYes. I did it that way in my test because that's similar to how I plan to use this in my application. I'm measuring the amps on a big 12 volt battery. In that setup, the 12 volts from the battery goes through a LM7805 voltage regulator. The output from the regulator supplies the 5 volts to an Arduino and INA282 . The shunt will be connected to the negative battery terminal and the load. So the negative side of the shunt is the same as my circuit's ground connection.Can you explain why this might be my problem? I'm not really clear on what "the 0.064V isn't within the part's common mode range" really means.

author: mcinque
author_rank: Unknown
timestamp: May 17, 2015, 02:31:35 pm
content: I'm using an INA214 (wich is similar to the 282) with a 1R 1% shunt and I read a clean output even with a small voltage drop.Even using isolated grounds for the shunt and for the power.Did you use the suggested schematic?How much ripple you have on the 5V rail?

author: scott216
author_rank: Regular Contributor
timestamp: May 17, 2015, 03:09:00 pm
content: Quote from: mcinque on May 17, 2015, 02:31:35 pmMy setup is similar, but in my setup REF2 and -IN both connect to GND. There's no ripple on the 5 volt supply, it's coming from my Rigol DP832 power supply. I'm also using the DP832 to simulate the voltage drop on shunt; this is coming from the 2nd output on the Rigol. I guess I could use a resistor voltage divider to simulate the shunt instead of using a 2nd output on the Rigol.

author: TiN
author_rank: Super Contributor
timestamp: May 17, 2015, 03:27:28 pm
content: Are you using kelvin connect routing for IN-/IN+ ?

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 17, 2015, 03:38:42 pm
content: Quote from: scott216 on May 17, 2015, 02:08:02 pmIf their grounds are connected then that's not the problem. I was just wondering if the two voltages were completely isolated from each other. In which case there would be no guarantee that the voltage you were applying to the sense pins was within the -14V to +80V range of the part.

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 17, 2015, 03:42:30 pm
content: Quote from: scott216 on May 17, 2015, 03:09:00 pmDon't forget that one of the channels on the DP832 is isolated from the others.

author: scott216
author_rank: Regular Contributor
timestamp: May 17, 2015, 04:24:57 pm
content: Quote from: TerminalJack505 on May 17, 2015, 03:42:30 pmI've got the grounds tied together on the breadboard. I did notice if I don't tie -IN to ground and I use the two DP832 outputs that are isolated, the output waveform does look better. P-P volts goes down to about 0.2 volts.

author: scott216
author_rank: Regular Contributor
timestamp: May 17, 2015, 10:45:49 pm
content: Quote from: TiN on May 17, 2015, 03:27:28 pmNo, I'm actually not measuring the voltage across the shunt, I'm simulating it be outputting a small voltage from my Rigol power supply.