Hello, Sparkfun community. I hope each of you is doing well. Perhaps one of you can clarify something for me regarding the AC723 current sensor (SEN-13679 ROHS) - or current sensor terminology in general. The product description states that the sensor measures both DC and AC currents up to 5 amps, but what does that mean exactly? The onboard chip uses the Hall Effect; so it is indeed bidirectional. However, according to the formula Peak = RMS*sqrt(2), the peak current for 5 amps AC is about 7.071 amps. This is greater than 5 amps DC, hence the reason for my confusion. I did not find any clarification in the specifications document. Your advice is appreciated; I don’t want to burn it. So, if this sensor does indeed handle 5 amps AC, then in actuality does it handle 7.071 amps DC? Or perhaps, if this sensor does indeed handle 5 amps DC, then in actuality does it only handle about 3.536 amps AC? After contacting customer service, I am lead to believe the former, since they say it will work with either 5 amps AC or DC. However, they did not provide more technical clarification than that. Thank you.
Instruments, devices & components with power ratings like this almost always take the peak values into account and simply use the RMS figures when specifying maximums.
5 amps AC is the average current, looks like the sensor saturates at 5A but more current shouldn’t hurt it so the current peaks at the top and bottom of the cycle won’t be an issue.
5A AC is going to read 5A just like 5A DC.
Thank you so much for your responses. After reading your replies and giving it some thought, it seems to me that the limiting factor is not necessarily the amperage, but rather the wattage. In other words, if too much power, then it will burn. When considering power as the limiting factor, then the product description makes sense. While the peaks of 5 amps AC are indeed greater than 5 amps, the RMS average would ultimately correspond to the same wattage as that of 5 amps DC. So, the sensor can handle the peaks of 5 amps AC, but it will burn if those peak values are sustained. The concept that I seem to have been missing is that too much wattage causes electronics to burn, not necessarily too much amperage. If my conclusion is wrong, please let me know. Again, thank you for your advice.
You can't have one without the other but it's current that heats things up. Take (but do not attempt!) the classic box wrench dropped on the terminals of the car battery. Prior to falling, the voltage was there. Only when the wrench conducts does the current flow. This does lead generate power but it's because of the current.KristoferKrisberg:
The concept that I seem to have been missing is that too much wattage causes electronics to burn, not necessarily too much amperage.
Thank you for that thought experiment - invokes the imagination. Perhaps classic to you, but I had never heard of it before. Thanks again to all of you for your advice. I consider this matter resolved.
On another note, how did you guys even notice my post, and so quickly!? Forgive me if this seems trivial, but I am new to the concept of online forums. In the same way you helped me, I feel a moral obligation to help someone else if I happen to know the answer to their questions. I always figure out everything on my own eventually. Sometimes it takes longer than I care to admit. So, I thought collaborating with others might be a better way. Hence, I gave this forum a try.
If you go to Forum/Unread Posts, you’ll get a list of the newest topics. Great way to see the latest things in the forum!