Timeline for What is the advantage of a current shunt ic versus a differential ADC across the shunt?
Current License: CC BY-SA 3.0
18 events
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| Aug 4, 2016 at 16:24 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jul 4, 2016 at 16:53 | comment | added | user57037 | There is another way to do current sensing. You can use a DC-rated hall effect sensor. One example is the ACS714. This helps mitigate the power dissipation problem with your shunt. | |
| Jul 4, 2016 at 14:20 | answer | added | John Birckhead | timeline score: 1 | |
| Jul 4, 2016 at 11:46 | comment | added | Neil_UK | What is your application? This will tell you what your needed accuracy is. Then we can work from there to see what components and techniques can deliver that accuracy. What is 'normal'? My DMM ammeter quotes about +/- 2%. If I need better than that then I am probably working in calibration standards lab, rather than asking questions on a hobby site. | |
| Jul 4, 2016 at 11:19 | comment | added | Bimpelrekkie | @dim I fully agree with this not be an easy design, certainly not something for an inexperienced person. To reduce the noise I would use filtering and/or averaging if possible (not slowing down the measurement too much). | |
| Jul 4, 2016 at 10:41 | comment | added | dim | @FakeMoustache Calibration can certainly help, but at the levels required by the OP (0.01A in 5mOhm is 50µV), noise may be significant. And noise cannot be calibrated out. Design will certainly not be easy. | |
| Jul 4, 2016 at 10:37 | comment | added | Bimpelrekkie | The 1% reading accuracy is caused by the offsets so if you calibrate these out you can get below the 1% accuracy. Please read: meettechniek.info/measurement/accuracy.html to gain an understanding | |
| Jul 4, 2016 at 10:31 | comment | added | Peter | The second option :). But if calibration can only remove offsets, if the reading itself is only 1% accurate how would calibration make this more accurate. Or is most of the inaccuracy due to offsets. | |
| Jul 4, 2016 at 10:29 | comment | added | Bimpelrekkie | Yes: write down the tolerances for the whole chain. But again, do you want to build something that is immediately 0.04% accurate ? If yes, it will cost you a lot. Or will you build a setup with 5% accuracy but then calibrate it to be 0.01% accurate ?? The second is much cheaper. | |
| Jul 4, 2016 at 10:27 | comment | added | Peter | Is there anywhere I can learn how to calculate accuracy with multiple components? | |
| Jul 4, 2016 at 10:24 | comment | added | Bimpelrekkie | There is no "normal", when I design circuits for use in an IC I have to design with components with tolerances up to 20 %. On a PCB I could have 1% resistors. An expensive bench multimeter might have a 0.01% base tolerance. There is no "normal" it depends on the circumstances and what you can afford (smaller tolerance components become exponentially more expensive). | |
| Jul 4, 2016 at 10:20 | comment | added | Bimpelrekkie | You do not need overall 0.04% intrinsic tolerance/accuracy as long as you can calibrate. Also component drift can be calibrated out but when using components with a high drift (they change properties over time) you will have to calibrate more often. | |
| Jul 4, 2016 at 10:20 | comment | added | Peter | I've found a resistor with .1% accuracy. I'm just trying to get the best accuracy I can. What is the normal accuracy that people measure to? | |
| Jul 4, 2016 at 10:18 | comment | added | dim | 0.01A accuracy over 25A is 0.04%. So, to ensure this, the first thing that comes to my mind is the tolerance of the shunt resistor. Did you actually find a 5mOhm resistor with 0.04% tolerance? I'm not sure what you want to achieve is realistic. | |
| Jul 4, 2016 at 10:17 | comment | added | Bimpelrekkie | Instead of "throwing" a more accurate (is it really more accurate ??) component in your design, you need to think about the tolerances in the complete system. The INA169 is a completely different component than the ADs1115 so how can those be compared ? You should learn about tolerances and accuracies first before you can have a meaningful discussion about these. You can build a better than 1% setup with the INA169 if you calibrate it. | |
| Jul 4, 2016 at 10:14 | comment | added | Peter | With the current sense amplifier chip, I would measure the output with an ADC. However with the differential ADC, I can just measure the voltage differential of the shunt resistor without the chip. I'm wondering if that is actually possible. | |
| Jul 4, 2016 at 10:12 | comment | added | PlasmaHH | One chip is an ADC, the other produces a current proportional to the input voltage differential. Two totally different applications, not sure why you try to compare them. | |
| Jul 4, 2016 at 10:06 | history | asked | Peter | CC BY-SA 3.0 |