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| Current sense shunt resistor on high current pcb |
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| cmorgan:
Hello! I have a high current pcb, 2oz copper, 7.5mm wide traces each side, designed to comfortably carry 30A @ 240VAC. I'd like to add a shunt resistor to measure current on the pcb. Resistances from 0.0003 to 0.0001 ohms keep total power below 4W but all of these are surface mount like https://www.digikey.com/product-detail/en/stackpole-electronics-inc/CSS2725FTL250/CSS2725FTL250CT-ND/1923235 Given that I have the 2oz traces on the top and bottom of the pcb how should I handle adding that shunt resistor? Vias to pull the trace to one side of the board, through shunt resistor and then vias on the other side to go back to traces on both sides? Chris |
| 001:
--- Quote from: cmorgan on November 12, 2018, 02:01:33 pm ---Hello! I have a high current pcb, 2oz copper, 7.5mm wide traces each side, designed to comfortably carry 30A @ 240VAC. I'd like to add a shunt resistor to measure current on the pcb. Resistances from 0.0003 to 0.0001 ohms keep total power below 4W but all of these are surface mount like https://www.digikey.com/product-detail/en/stackpole-electronics-inc/CSS2725FTL250/CSS2725FTL250CT-ND/1923235 Given that I have the 2oz traces on the top and bottom of the pcb how should I handle adding that shunt resistor? Vias to pull the trace to one side of the board, through shunt resistor and then vias on the other side to go back to traces on both sides? Chris --- End quote --- use standard 4 wire reading |
| coppice:
How accurately do you need to measure the current? It matters a lot in these designs. If you want a rough estimate (say 5%) lots of things will work. If you want decent accuracy (<1%) you will need to take great care to achieve a good 4 wire connection (whether you use an actual 4 wire shunt device or not), and you'll either need to avoid the shunt heating too much, or pay a lot for a shunt with an extremely good temperature coefficient. |
| cmorgan:
--- Quote from: 001 on November 12, 2018, 03:04:21 pm ---use standard 4 wire reading --- End quote --- Hi 001. Would you explain what you mean by a 4 wire reading? If it helps this is a single phase two wire, so I have either L / N or L1 / L2 through the device. I didn't want to put two shunt resistors, one on the top and one on the bottom as then I'd have to sum up the current through the two paths. I'm looking at using ATM90E26 for the measurements. Chris |
| Marco:
More like 10 vias, or you could use two shunts and then just resistively combine the outputs. PS. actually on second though, can't easily combine the outputs resistively since you don't have a good common ground. |
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