Quote:
Originally Posted by Alan Anderson
That might be true if using an inductive sensor, but a Hall effect transducer responds to magnetic flux directly. The ring is not acting as a transformer element, but as a flux concentrator, and does need to be ferrous.
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We use a lot of commercially made Hall Effect current sensors at work. They all have ferrous flux concentrators. For certain applications, we get custom sensors made with special ferrous materials that work to higher frequencies than the silicon-steel they normally use.
Quote:
Originally Posted by GeeTwo
For anyone trying to implement this --the voltage produced by the ring (which merely needs to be conductive, not ferrous) is directly related to the RATE OF CHANGE of the current. You will need to keep a running total of the voltage to get a good value for current draw. I don't see how you're going to keep from having significant drift in a practice session unless you pause and recalibrate regularly, though perhaps over the duration of an FRC match it wouldn't be too bad. This trick works well for A/C meters because the current is constantly changing (and adds up to zero), so that the average voltage induced over a 1/60 sec cycle is proportional to the RMS current flow. For DC, no such luck - if you draw a steady curent, whether 1A or 110A, the voltage will be zero after it stabilizes.
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Change to a ferrous ring then use an oscilloscope to check the output of your homemade sensor again. You may want to compare the output of your homemade sensor against the output of a commercially available current sensor that is capable of reading DC; i.e. a current clamp probe. Depending on what you are trying to do and your accuracy requirements, you may have to calibrate your sensor against a known standard.
You may be much happier using a commercially made sensor such as the one in the link below.
http://www.digikey.com/product-detai...168-ND/4990649
LEM has put a lot of hard work into reducing the inherent drift in the offset voltage (over temperature and time) and to linearize the output. For comparison, the SS49E/SS59ET Series from Honeywell has an effective offset of +-10% at 25 C. It is likely to be worse at other temperatures. There is no spec for linearity.
Get in touch if you want help choosing a commercially made Hall Effect current sensor.