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A1360 Datasheet(PDF) 22 Page - Allegro MicroSystems |
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A1360 Datasheet(HTML) 22 Page - Allegro MicroSystems |
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22 / 25 page 
A1360, A1361, and A1362 To construct a current sensor using the A136x, first consider a current carrying wire that we want to observe. As dictated by Ampere’s Law, a magnetic field is produced around the wire that is proportional to the amount of current flowing through the wire. By passing this wire through a soft magnetic core, the magnetic flux produced by the wire can be concentrated and directed through a gap in the core. The magnetic flux density can be measured by inserting the A136x SIP into the gap in the core. As a result, the output of the A136x device will be proportional to the amount of current flowing through the wire. The example feedthrough current sensing setup shown below (figure 7) has a core made of “mu metal” that is 2 mm thick and 4 mm wide. The inner radius of the core is 14.5 mm and the outer radius is 18.5 mm. The wire going through the center of the core has a radius of 9 mm. Using this setup with a gap of 1.7 mm, a field strength results that is on the order of 7 G /A at the Hall element in the A136x. The recommended core material for construction of the concen- trator depends on the specific application. If high flux saturation is desired, then an alloy such as HyPerm49 is recommended. For lower-current level sensing applications, a material such as HyMu80 may be desired. (HyMu80 has lower magnetic flux saturation than HyPerm49, therefore more HyMu80 mate- rial is required to carry the same amount of flux compared to Hyperm49.) If frequency response is a concern, then eddy currents can be reduced by either laminating the HyPerm49 or HyMu80 alloys, or by using a ferrite core. Constructing a Current Sensor Using the A136x Ø18 mm 4 mm 2 mm Ø37 mm Application-specific housing Ring concentrator Current-conducting wire A136x Center Hall element in gap 1.7 mm Figure 7. The example current sensor setup used to generate the data in this section was constructed with a split-ring concentrator and an A136x device. A copper wire was fed through the concentrator, and the A136x placed in its gap. This approximates a typical ammeter application on a thick wire, such as shown in the left view. Note that such applications usually have a protective housing, which should be taken into consideration when designing the final application. The housing is beyond the scope of this example. Low-Noise Programmable Linear Hall Effect Sensor ICs with Adjustable Bandwidth (50 kHz Maximum) and Analog Output 22 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com |
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