The LNVR Series
LNVR-BX-01HS An LNVR including the low pass filter to reduce noise above 10 Hz. mounted in a plastic Hammond box with dual banana jacks for power in and reference voltage out with the high stability option. The low pass filter can be particularly important in digitizing applications such as in calibrating ADCs. A new circuit topology (U.S. Patent No. 7,382,179*) exploits both the advantages of the internal OpAmp and scaling network of an AD587LN monolithic voltage reference and the high stability of an ovenized reference diode, here an LM399H. The resulting composite circuit has a temperature coefficient near typical room temperatures of about 1 ppm / ºC. Sensitivity to power supply voltage is also greatly improved to less than 1 ppm / Volt. 10V LNVR-BX-01HS Sold out; 1V LNVR-BX-01HS (derived from our original 1V LNVR board) Sold out (3 ppm / ºC) .
The main low pass filter is arranged as a classic electrolytic stack where leakage is minimized by reducing the voltage across the top cap to near zero. The design is along the lines of the Analog Devices reference design (no affiliation) in the Analog Devices 2004 "Analog-Digital Conversion" book edited by Walt Kester (See Figure 7.19 and bottom page 21, Combining Low-Noise Amplifier With Extensive Filtering Yields Exceptional Reference Noise Performance)
Short term transfer accuracy: better than +/- .0005% absolute (+/- 5 ppm).
All reference boards and boxes are calibrated to within +/- 10 uV absolute and guaranteed to remain longer term (6 months) within +/- 500 uV (+/- .005%) of absolute as rated.
Extra trim resistors are added to narrow the trim range for easier calibration. Calibration data is reported to 10 uV resolution (.0001%).
For the LNVR -01HS, there less sensitivity to power supply voltage and tempcos are reduced over references based on the AD587 alone.
*We have decided for commercial reasons to allow the '179 patent to expire, rather than pay the renewal fees.
All checks and money orders should be made payable to "GELLER"; please see our ordering page for more information.
Our Low Cost Voltage Transfer Project for Amateur Scientists, Electronics Hobbyists, and Schools, was Supported in Part by Analog Devices Incorporated. Please visit the Analog Devices website!
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