Voltage References

GELLER Labs Voltage Reference Catalog

(be sure to hit refresh to see our latest changes!)

Welcome to a catalog of voltage references currently available from GELLER engineering. We offer basic reference boards as both assembled and calibrated printed circuit boards. Delivery ranges from off the shelf to two weeks, depending on current stock. All references come with a certificate of calibration that is NIST traceable through our Fluke 732B transfer standard.

Note: December 2011, our Fluke 732B transfer standard is back from annual calibration at Fluke, this year over $600 including round trip overnight shipping.

The temperature coefficient, or "tempco", is a measure of how much the output voltage can change in voltage with changes in ambient temperature. Most manufacturers specify tempco in parts per million (ppm) per degree C. Since this is a fractional representation, the actual change in voltage per degree C is a function of the reference voltage. For example, a millionth of 10 V is 10 uV therefore 1 ppm / degree C is the same as 10 uV / degree C for a 10 V reference.

All "L" grade and better 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%). The last digit of resolution will only be useful in the short term at the reported temperature and at the specified power supply voltage (15V for 10V references). Under these conditions, it is possible to obtain short term transfer accuracy of better than +/- .0005% absolute (+/- 5 ppm).

We try to be very clear about what this project is about. We are attempting to provide a low cost absolute voltage calibration point targeted to the amateur scientist, electronics hobbyists, consultants, and schools. Our SVR product is a high quality platform for the AD587 family (in our opinion) some of the best voltage reference chips ever made.

We call the SVR board a "transfer reference". The SVR board is a high quality platform for a monolithic reference chip, nothing more. Since first offered in 2004, many hundreds of SVR boards are now in use world wide.

Our Fluke 732B, even with its FLUKE NIST traceable calibration, in the art of metrology, is generally referred to as a "transfer standard".

The SVR board is intended to give a small lab a way to verify their 10 V calibration point to better than 10 ppm (100 uV absolute). Our field tests have done considerably better, however 10 ppm is our conservative spec. Since the SVR board is rated at 5 ppm/c, the board should be used at about the same temperature as we calibrated the board (as reported) after a warm-up period and at about 15V. The reference chips we use are rated at 100 uV / V (power supply), however most perform much better.

Our LNVR references with the 01HS high stability option (U.S. Patent No. 7,382,179*) have the lowest tempcos.

The specifications are, for all practical purposes, the specs of the chip itself, and is not degraded below spec by our precision trim circuit which uses high quality IRC 0.1% 20 ppm/c trim resistors (the 20 ppm/c is per resistor, not tracking, and it is of the trim range, thus not deteriorating the board 5 ppm/c rating, and the 100 ppm/c trimmer is a small fraction of the IRC trim Rs). The boards are burned in for 200+ hours before final calibration. Final calibration is done with our Agilent 34410A and/or FLUKE 845AR null meter referenced to the 732B. (A "calibrated" hp or Agilent 3458A -alone- is no longer sufficient at 10 ppm absolute and below.)

The details of high precision use, 30 to 60 minute warm-up, use as close the temperature where we did the calibration, power supply voltage of 15V +/- 0.1V are all just to squeak the last ppms possible (to get as close as possible to our 732B voltage) using this relatively inexpensive method. At relatively low precision (e.g. 0.01%), these are all non-issues.

Any of our reference products can be re-calibrated on request for $10 plus shipping ($4.95 for priority mail). A six month calibration interval is recommended for all models. This item applies only to our products, we are not able to calibrate other items.

*We have decided for commercial reasons to allow the '179 patent to expire, rather than pay the renewal fees.

The SVR

The LNVR

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!

Geller Labs	Geller Labs
Products	GELLER Labs Voltage Reference Catalog (be sure to hit refresh to see our latest changes!) Welcome to a catalog of voltage references currently available from GELLER engineering. We offer basic reference boards as both assembled and calibrated printed circuit boards. Delivery ranges from off the shelf to two weeks, depending on current stock. All references come with a certificate of calibration that is NIST traceable through our Fluke 732B transfer standard. Note: December 2011, our Fluke 732B transfer standard is back from annual calibration at Fluke, this year over $600 including round trip overnight shipping. The temperature coefficient, or "tempco", is a measure of how much the output voltage can change in voltage with changes in ambient temperature. Most manufacturers specify tempco in parts per million (ppm) per degree C. Since this is a fractional representation, the actual change in voltage per degree C is a function of the reference voltage. For example, a millionth of 10 V is 10 uV therefore 1 ppm / degree C is the same as 10 uV / degree C for a 10 V reference. All "L" grade and better 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%). The last digit of resolution will only be useful in the short term at the reported temperature and at the specified power supply voltage (15V for 10V references). Under these conditions, it is possible to obtain short term transfer accuracy of better than +/- .0005% absolute (+/- 5 ppm). We try to be very clear about what this project is about. We are attempting to provide a low cost absolute voltage calibration point targeted to the amateur scientist, electronics hobbyists, consultants, and schools. Our SVR product is a high quality platform for the AD587 family (in our opinion) some of the best voltage reference chips ever made. We call the SVR board a "transfer reference". The SVR board is a high quality platform for a monolithic reference chip, nothing more. Since first offered in 2004, many hundreds of SVR boards are now in use world wide. Our Fluke 732B, even with its FLUKE NIST traceable calibration, in the art of metrology, is generally referred to as a "transfer standard". The SVR board is intended to give a small lab a way to verify their 10 V calibration point to better than 10 ppm (100 uV absolute). Our field tests have done considerably better, however 10 ppm is our conservative spec. Since the SVR board is rated at 5 ppm/c, the board should be used at about the same temperature as we calibrated the board (as reported) after a warm-up period and at about 15V. The reference chips we use are rated at 100 uV / V (power supply), however most perform much better. Our LNVR references with the 01HS high stability option (U.S. Patent No. 7,382,179) have the lowest tempcos. The specifications are, for all practical purposes, the specs of the chip itself, and is not degraded below spec by our precision trim circuit which uses high quality IRC 0.1% 20 ppm/c trim resistors (the 20 ppm/c is per resistor, not tracking, and it is of the trim range, thus not deteriorating the board 5 ppm/c rating, and the 100 ppm/c trimmer is a small fraction of the IRC trim Rs). The boards are burned in for 200+ hours before final calibration. Final calibration is done with our Agilent 34410A and/or FLUKE 845AR null meter referenced to the 732B. (A "calibrated" hp or Agilent 3458A -alone- is no longer sufficient at 10 ppm absolute and below.) The details of high precision use, 30 to 60 minute warm-up, use as close the temperature where we did the calibration, power supply voltage of 15V +/- 0.1V are all just to squeak the last ppms possible (to get as close as possible to our 732B voltage) using this relatively inexpensive method. At relatively low precision (e.g. 0.01%), these are all non-issues. Any of our reference products can be re-calibrated on request for $10 plus shipping ($4.95 for priority mail). A six month calibration interval is recommended for all models. This item applies only to our products, we are not able to calibrate other items. We have decided for commercial reasons to allow the '179 patent to expire, rather than pay the renewal fees. The SVR The LNVR 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! COPYRIGHT © 2005, 2009, 2010 JOSEPH M. GELLER, All rights reserved.
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