Low cost Voltage References
Malone Electronics
www.voltagestandard.com
418 W. Main St. #1542
Battle Ground, WA 98604 USA
email: doug@voltagestandard.com
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How Accurate is your DC Voltmeter?
Find out with our low cost voltage references
Find out with our low cost voltage references
Model VREF5-01 Precision
Voltage Reference
This small, portable, precision voltage reference can be used to check the calibration of your DVM or DMM. Different voltage models are available but our most popular is 5.000V and is described here.The VREF5-01 features a 5.000V output, accurate within 0.01% (output guaranteed to be between 4.9995 and 5.0005 Volts) for a minimum of 6 months. The circuit is based on the Texas Instruments' REF5050ID Voltage Reference. Here is a link to the data sheet on the TI web site: http://focus.ti.com/lit/ds/symlink/ref5050.pdf
The circuit board was designed to minimize the effects of mechanical stress on the reference IC. Specifically, the REF5050 was placed on the edge of the board and 2 adjacent slots decouple stresses in the board from reaching the reference which could otherwise cause the output voltage to shift.
The REF5050 is carefully and quickly soldered to the board and every one of the references that we have sold easily exceed the specifications listed above.
An external power supply is not needed; The included 9V battery makes the unit self-contained and easily transported. An on-board on/off switch allows you to maximize battery life when not in use. Reverse polarity protection is included, so even if the battery is placed in the holder backwards no damage will result. A high brightness, low current LED clearly indicates when the reference is turned on.
The worst-case change with temperature is a low 5ppm / oC or only +- 65uV / oC. The reference chip itself has a temperature coefficient of 3ppm and the output trim adjustment adds another approximately 2ppm. Before shipping, the ambient temperature and output voltage are recorded as explained below. To guarantee a 5V output within .01%, your ambient temperature must be within 8oC (14oF) of the stated calibration temperature. In a typical indoor environment this usually isn't much of a restriction.
After the unit is assembled, it is powered up with a 9.0V power supply for a minimum of 250 hours to "age" the reference and improve its long term stability. After aging, the trim potentiometer is carefully adjusted so that the reference voltage is within 5µV of 5.00000V as measured by our calibrated, 8.5 digit Keysight 3458A DMM. (Keysight Technologies, Loveland Standards Laboratory, Certificate of Calibration 1-10871332528-1, valid through February 27,2020). The ambient temperature is also recorded (typically 21oC).
This reference circuit is very similar to what was described in our article in the September 2007 issue of Nuts and Volts magazine, "Build a .01% Accurate Voltage Reference" http://nutsvolts.texterity.com/nutsvolts/200709/?folio=52. The Nuts and Volts reference was based on the Intersil X60008 reference chip and numerous reference assemblies were sold through eBay. Unfortunately, Intersil has discontinued production of the X60008 and it is no longer available. The REF5050 is vastly superior to the X60008, and most other reference chips, in one respect: line regulation. The X60008 output voltage could vary as much as 100uV for every volt away from its 'sweet spot' of 6.5V input. The REF5050 output is guaranteed, however, to vary only 5uV per Volt. In practical terms this means that with a fresh 9V battery and a 5.00000V output, when the battery gets down to, say, 6V the output will have changed only 15uV!
Recalibration of the REF5-01 is free for the first two years after purchase - just mail it back to us and send a $7.00 PayPal payment to doug@voltagestandard.com for return USPS Priority shipping to destinations within the USA.. After two years the calibration charge is $5.00 plus shipping.
2.048V, 2.500V, 3.000V, 4.096V, and 4.500V references are also available; please specify desired voltage when placing order.
Prices and specifications subject to change without notice.