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AD698: Universal LVDT Signal Conditioner Data Sheet (Rev. C)7/30/1993PDF194 K
Alternative Parts
Overview
Features and Benefits
- Single Chip Solution, Contains Internal Oscillator and Voltage Reference
- No Adjustments Required
- Interfaces to Half-Bridge, 4-Wire LVDT
- DC Output Proportional to Position
- 20 Hz to 20 kHz Frequency Range
- Unipolar or Bipolar Output
- Will Also Decode AC Bridge Signals
- Outstanding Performance
Linearity: 0.05%
Output Voltage: ±11 V
Gain Drift: 20 ppm/°C (typ)
Offset Drift: 5 ppm/°C (typ)
Product Details
The AD698 is a complete, monolithic Linear Variable Differential Transformer (LVDT) signal conditioning subsystem. It is used in conjunction with LVDTs to convert transducer mechanical position to a unipolar or bipolar dc voltage with a high degree 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 opposed 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 secondary 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 approaches to LVDT interfacing. The benefits of this new circuit 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 |
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Product Lifecycle
Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Documentation & Resources
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CN-0301: Universal LVDT Signal Conditioning Circuit12/5/2013PDF313 kB
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Linear Variable Differential Transformers8/1/2008 Analog Dialogue
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LVDT Interfaces Offer Choice of Analog or Digital Output1/1/1994 Analog Dialogue
Reference Designs (1)
Design Resources
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PCN-PDN Information
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