LVDT Signal a Conditioner AD598 FUNCTIONAL BLOCK DIAGRAM FEATURES Single Chip Solution, Contains Internal Oscillator and Voltage Reference EXCITATION (CARRIER) No Adjustments Required 3 2 Insensitive to Transducer Null Voltage Insensitive to Primary to Secondary Phase Shifts V A 11 DC Output Proportional to Position OSC AMP 20 Hz to 20 kHz Frequency Range Single or Dual Supply Operation AD598 17 Unipolar or Bipolar Output Will Operate a Remote LVDT at Up to 300 Feet AB V 16 FILTER AMP OUT Position Output Can Drive Up to 1000 Feet of Cable A+B 10 LVDT Will Also Interface to an RVDT V B Outstanding Performance Linearity: 0.05% of FS max Output Voltage: 611 V min Gain Drift: 50 ppm/8C of FS max Offset Drift: 50 ppm/8C of FS max PRODUCT HIGHLIGHTS 1. The AD598 offers a monolithic solution to LVDT and PRODUCT DESCRIPTION RVDT signal conditioning problems few extra passive com- The AD598 is a complete, monolithic Linear Variable Differen- ponents are required to complete the conversion from me- tial Transformer (LVDT) signal conditioning subsystem. It is chanical position to dc voltage and no adjustments are used in conjunction with LVDTs to convert transducer mechan- required. ical position to a unipolar or bipolar dc voltage with a high degree of accuracy and repeatability. All circuit functions are 2. The AD598 can be used with many different types of included on the chip. With the addition of a few external passive LVDTs because the circuit accommodates a wide range of components to set frequency and gain, the AD598 converts the input and output voltages and frequencies the AD598 can raw LVDT secondary output to a scaled dc signal. The device drive an LVDT primary with up to 24 V rms and accept sec- can also be used with RVDT transducers. ondary input levels as low as 100 mV rms. The AD598 contains a low distortion sine wave oscillator to 3. The 20 Hz to 20 kHz LVDT excitation frequency is deter- drive the LVDT primary. The LVDT secondary output consists mined by a single external capacitor. The AD598 input sig- of two sine waves that drive the AD598 directly. The AD598 nal need not be synchronous with the LVDT primary drive. operates upon the two signals, dividing their difference by their This means that an external primary excitation, such as the sum, producing a scaled unipolar or bipolar dc output. 400 Hz power mains in aircraft, can be used. The AD598 uses a unique ratiometric architecture (patent pend- 4. The AD598 uses a ratiometric decoding scheme such that ing) to eliminate several of the disadvantages associated with primary to secondary phase shifts and transducer null voltage traditional approaches to LVDT interfacing. The benefits of this have absolutely no effect on overall circuit performance. new circuit are: no adjustments are necessary, transformer null 5. Multiple LVDTs can be driven by a single AD598, either in voltage and primary to secondary phase shift does not affect sys- series or parallel as long as power dissipation limits are not tem accuracy, temperature stability is improved, and transducer exceeded. The excitation output is thermally protected. interchangeability is improved. 6. The AD598 may be used in telemetry applications or in hos- The AD598 is available in two performance grades: tile environments where the interface electronics may be re- mote from the LVDT. The AD598 can drive an LVDT at Grade Temperature Range Package the end of 300 feet of cable, since the circuit is not affected by phase shifts or absolute signal magnitudes. The position AD598JR 0C to +70C 20-Pin Small Outline (SOIC) output can drive as much as 1000 feet of cable. AD598AD 40C to +85C 20-Pin Ceramic DIP 7. The AD598 may be used as a loop integrator in the design of It is also available processed to MIL-STD-883B, for the military simple electromechanical servo loops. range of 55C to +125C. REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Tel: 617/329-4700 Fax: 617/326-8703AD598* PRODUCT PAGE QUICK LINKS Last Content Update: 02/23/2017 COMPARABLE PARTS DISCUSSIONS View a parametric search of comparable parts. View all AD598 EngineerZone Discussions. DOCUMENTATION SAMPLE AND BUY Data Sheet Visit the product page to see pricing options. AD598: LVDT Signal Conditioner Data Sheet TECHNICAL SUPPORT AD598: Military Data Sheet Submit a technical question or find your regional support number. REFERENCE DESIGNS CN0288 DOCUMENT FEEDBACK Submit feedback for this data sheet. DESIGN RESOURCES AD598 Material Declaration PCN-PDN Information Quality And Reliability Symbols and Footprints This page is dynamically generated by Analog Devices, Inc., and inserted into this data sheet. A dynamic change to the content on this page will not trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified.