Ad698ap Universal Lvdt Signal Conditioner Adi 

AD698AP Universal LVDT Signal Conditioner ADI

AD698AP Universal LVDT Signal Conditioner ADI

PRODUCT DESCRIPTION
The AD698 is a complete, monolithic Linear Variable Differen-
tial Transformer (LVDT) signal conditioning subsystem. It is
used in conjunction with LVDTs to convert transducer mechan-
ical position to a unipolar or bipolar dc voltage with a high de-
gree of accuracy and repeatability. All circuit functions are
included on the chip. With the addition of a few external passive
components to set frequency and gain, the AD698 converts the
raw LVDT output to a scaled dc signal. The device will operate
with half-bridge LVDTs, LVDTs connected in the series op-
posed configuration (4-wire), and RVDTs.
The AD698 contains a low distortion sine wave oscillator to
drive the LVDT primary. Two synchronous demodulation
channels of the AD698 are used to detect primary and second-
ary amplitude. The part divides the output of the secondary by
the amplitude of the primary and multiplies by a scale factor.
This eliminates scale factor errors due to drift in the amplitude
of the primary drive, improving temperature performance and
stability.
The AD698 uses a unique ratiometric architecture to eliminate
several of the disadvantages associated with traditional ap-
proaches to LVDT interfacing. The benefits of this new cir-
cuit are: no adjustments are necessary; temperature stability is
improved; and transducer interchangeability is improved.
The AD698 is available in two performance grades:
Grade Temperature Range Package
AD698AP –40°C to +85°C 28-Pin PLCC
AD698SQ –55°C to +125°C 24-Pin Cerdip