Analog Devices Inc. AD698 Universal LVDT Signal Conditioner
Analog Devices AD698 Universal LVDT Signal Conditioner is a complete monolithic signal conditioning subsystem that converts LVDT mechanical position into a unipolar or bipolar DC output with high accuracy and repeatability. The device integrates all active circuit functions on a chip and requires only a few external passive components to set the operating frequency and gain.
A low-distortion sine-wave oscillator excites the LVDT primary, while two synchronous demodulation channels detect the primary and secondary amplitudes for ratio-based output processing. The ADI AD698 Universal LVDT Signal Conditioner uses a ratiometric architecture that reduces scale factor errors caused by primary drive drift, improves temperature stability, and increases transducer interchangeability without adjustment.
The AD698 Signal Conditioner operates with half-bridge LVDTs, series-opposed 4-wire LVDTs, and RVDTs in precision position sensing systems. The AD698 is available in a 40-lead LFCSP package for -40°C to +85°C operation and a 24-lead CERDIP package for -55°C to +125°C operation.
Features
- Single-chip solution with internal oscillator and voltage reference
- No adjustments required
- Interfaces to half-bridge and 4-wire LVDTs
- DC output proportional to position
- 20Hz to 20kHz operating frequency range
- Unipolar or bipolar output capability
- Decodes AC bridge signals
- Superior performance
- 0.05% linearity
- ±11V output voltage range
- Grade temperature range package
- 40-lead LFCSP -40°C to +85°C
- 24-lead CERDIP -55°C to +125°C
Applications
- LVDT position measurement systems
- RVDT signal conditioning
- Half-bridge transducer interfaces
- Electromechanical servo loop designs
- AC bridge signal conditioning
Specifications
- Operates with half-bridge LVDTs, series-opposed 4-wire LVDTs, and RVDTs
- Gain drift 20ppm/°C typical of full scale
- Offset drift 5ppm/°C typical of full scale
- Common-mode rejection with ±3V common-mode input, gain 50ppm/V typical, offset 320ppm/V typical
- Meets specifications with input levels as low as 100mVrms
- Excitation voltage ranges from 2.1Vrms to 24Vrms, depending on resistor selection
- Excitation short-circuit current 30mArms to 60mArms typical, depending on configuration
- Dual supply operation supports ±13V to ±18V rails, single-supply operation supports 13V to 36V
- 40-lead LFCSP and 24-lead CERDIP package options
BLOCK DIAGRAMs
