NVE Sensor and Isolator News
March 2009
In This Issue

Magnetic Gradiometers

Application Corner

Symposium in Germany


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NVE In the News
Aktuel Elektronik
The advantages of NVE IsoLoop isolators compared to optocouplers were summarized in a full-page article in the February issue of the Danish magazine Aktuel Elektronik. The article was written by Rolf Pedersen of Rhopoint Nordic Aps.
<Links to this and other articles about NVE>


NVE 20th Anniversary
Birthday Cake
NVE celebrates
 20 years of
   leadership this month. The company was founded March 8, 1989 as Nonvolatile Electronics by spintronics pioneer Dr. James M. Daughton. The company's name was formally changed to NVE Corporation when it became public in 2000.
<NVE’s Historical Highlights>


Spring Forward
Spring Forward
Daylight
 Saving Time
begins Sunday, March 8. Set your clocks forward an hour.
Featured Product Line
Magnetic Gradiometers

Many engineers are familiar with magnetometer magnetic sensors, which determine magnetic field strength. Magnetic gradiometers are less well known but every bit as useful.

NVE gradiometers use arrays of four Giant Magnetoresistance (GMR) sensors to sense field gradients between the sensor elements. The elements are electrically configured as a Wheatstone bridge.

Gradiometers can be used to detect magnetic or ferrous targets. A biasing magnet is used for detecting proximity to a moving ferrous target. The gradiometer’s output can be also shaped with external flux shaping devices (flux guides).

Three gradiometer part types are in standard stock for immediate delivery:

Part
Number
Linear
Range
(|Oe|)
Satur-
ation
(|Oe|)
Element
Spacing
(mm)
Typical
Resis-
tance
(Ohms)
Package
Min.
Max.
AB001-02
20
200
250
0.5
2.5 K
SOIC8
AB001-00
20
200
250
0.5
2.5 K
MSOP8
ABH001-00
5.0
40
70
0.5
1.2 K
MSOP8

Parts are available in either lead (Pb) or RoHS versions (as with all NVE parts, RoHS is specified with an “E” suffix).

An evaluation kit with an assortment of gradiometers, magnetometers, and magnets is also available.

<Links to Gradiometer Data Sheets>
 
Application Corner
Isolated ADC Using an IL514
IsoLoop--The Opto Alternative
By Sandy Templeton
Director, Isolator Product Development and Applications

Isolating grounds is critical to minimizing noise in Analog to Digital Converters.

Optocouplers aren’t used for high speed current routing in converter circuits because their parasitic capacitance adds more distortion and noise than the original circuit. Most non-optical isolators have high EMI, making them an unwelcome source of additional noise. IsoLoop isolators change all that and allow the designer to effectively segregate digital and analog ground current paths without additional noise:

Isolated ADC Using an IL514

A typical board layout using the a new IL514 three-channel isolator is shown below (an IL700-Series isolator can be used instead if extremely low pulse-width distortion is needed):

Isolated ADC Board Layout

The isolated ground of the IsoLoop isolator is connected to the analog reference ground of the circuit board, and all digital currents into and out of the ADC are from ADC digital I/O activity and are synchronized to the conversion clock or data clock. Unlike non-isolated circuits, there is no asynchronous noise injected into the ADC ground from the rest of the digital circuits on the board.

For more information on isolating data convertors, see Application Bulletin No. 14 (.pdf).

<More Isolator Applications>
 
Presentations
Sensors and Magnetic Systems Symposium

MR Symposium LogoNVE Vice President Jay Brown and HYLINE
Sensor-Tec President Christoph Kleye are coauthors
of a paper to be presented at the Magnetoresistive Sensors and Magnetic Systems Symposium in Wetzlar, Germany, March 31 through April 1.

The paper will be titled “Different GMR/TMR Devices and Integration Advancements.”

According to the Symposium organizers, authors are “a hand-picked selection of experts from around the world...” Peter Grünberg, a recipient of the 2007 Nobel Prize for Physics, is also on the program.

<Registration Information>


<More NVE Papers and Presentations>
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