I am preparing to layout a PCB. I have an ACS723, that I want to use to sense the current going through a relay. In addition to the relay I have a Meanwell IRM-12-20 to supply ac to dc voltage to the board.

According to the ACS app note:

The ACS723 works by sensing the magnetic field created by the current flowing through the package. However, the sensor cannot differentiate between fields created by the current flow and external magnetic fields. This means that external magnetic fields can cause errors in the output of the sensor.

Since the ACS will be detecting mains voltages, and that I want to have enough spacing between the high and low voltage sides of the circuit, the layout I had in mind restricts the placement of the ACS.

Overall, I am curious as to whether or not close physical proximity to either the AC/DC converter or relay will cause enough interference wrt the ACS readings?

Here is a partial of what I have come up with to give you an idea of the current layout.

enter image description here

  • \$\begingroup\$ so you have an unknown relay, with unknown frame structure, composition, and orientation, and unknown magnetic materials guiding the coil flux, and unknown currents and slewrates flowing thru unknown Nc and NC and armature nodes. And you need a prediction of the error to be expected, 9mm away over a PCB with unshown planes and skin depths. \$\endgroup\$ – analogsystemsrf Oct 19 '19 at 3:01
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    \$\begingroup\$ I'm not an electrical engineer, half the things you said made 0 sense. I'm generally just looking for a best guess not anything extremely scientific... much in the way that some components datasheets say keep this capacitor as close to the regulator as possible, keep this x away from that, make sure no switching lines are below this .etc. I do know the relay (part number T9A... above), however it doesn't really say anything about "coil flux". FYI the top of the picture is the top of the board. \$\endgroup\$ – Alex Oct 19 '19 at 3:53
  • \$\begingroup\$ Why not use a low value shunt resistor and sense the voltage across it? What is the expected current to be measured? \$\endgroup\$ – Ben Watson Oct 19 '19 at 5:28
  • \$\begingroup\$ Which Amp rating of the ACS723 are you using, what is the maximum current it needs to measure, and how accurate does it have to be? What is the frequency range? Does it include DC? Where is the AC/DC converter? \$\endgroup\$ – Bruce Abbott Oct 19 '19 at 5:58
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    \$\begingroup\$ Follow @BenWatson advice and use a low ohm shunt resistor. It is almost always better to do wired instead of wireless measurements regarding EMI \$\endgroup\$ – Stefan Wyss Oct 19 '19 at 13:37

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