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The VREF10-002 now operates from internal 9V batteries or an external 24VDC power supply
This small, portable, precision voltage reference can be used to check the calibration of your DVM or DMM. The VREF10-002 features a 10.0000V output, and is conservatively rated to be accurate within 0.002% for a minimum of 8 months. The circuit is based on the Linear Technology LT1021BCN8-10 which uses buried Zener technology resulting in excellent long term stability. Here is a link to the LT1021 datasheet on the Linear Technology website: https://www.analog.com/media/en/technical-documentation/data-sheets/1021fc.pdf
The VREF10-002 can either be powered by the 2 included RayOVac Alkaline 9V batteries or an external 24VDC power supply. When powered by the batteries the unit is completely self contained and easily transported. An on-board on/off switch allows you to maximize battery life when not in use. Current drain is less than 5mA so the batteries will last many 10's of hours. An on board voltage regulator supplies a constant input voltage to the LT1021 as the batteries slowly decrease to their replacement voltage of 7V. Reverse polarity protection is included, so even if one or both batteries is placed in their holder backwards, no damage will result. A red LED clearly indicates when the unit is powered on by internal batteries.
Buried Zener References become more stable the longer they are powered-up. Operation with an external 24VDC supply allows the VREF10-002 to be continuously powered without draining the batteries. An optional low cost, UL approved, linear, regulated power supply is available at our online store. Alternatively, you can use your own 24VDC supply (a linear, regulated supply is strongly recommended) with a 2.5mm/5.5mm plug. A lit low current red LED indicates battery operation and a lit orange LED indicates external power. The switchover from batteries to external supply (or vice -versa) is virtually instantaneous and when both are present preference is given to the external supply. Both the battery and external power inputs are reverse polarity protected and can withstand up to +/- 40V without damage.
Temperature compensation keeps the VREF10-002 temperature coefficient to less than +/- 0.9ppm/C over the range of 60ºF to 90ºF (16C to 32C ). The temperature stability is verified by our thermal chamber slowly changing the temperature from 60ºF to 90ºF over a period of 8 hours and measuring the Reference output every 0.1ºF
The temperature graph for your particular VREF10-002 is available as an option via our online store.
After the unit is assembled, it is powered up with for a minimum of 2000 hours to "age" the reference and confirm its long term stability. During this aging process, daily measurements are made of the reference output voltage- the LT1021 is replaced on those units that have excessive long term drift. After aging, a trim pot is carefully adjusted so that the output voltage is within 5uv of 10.000000V as measured by our calibrated, 8.5 digit Keysight 3458A DMM. (Keysight Certificate of Calibration 1-14089272324-1, valid through March 3, 2022). The ambient temperature is recorded and unless specified otherwise will be in the range 68 to 70 degrees F. We can perform calibration at other temperatures- please inquire for feasibility and pricing.
For maximum accuracy it is recommended that the reference be powered-up 15 minutes before use.
The VREF10-002 optional enclosure (shown below) provides the following:
• Same circuitry and electrical specifications as the basic VREF10-002 PCB
• Black plastic enclosure surrounds 9V batteries mounted underneath circuit board
• Small rubber feet in bottom corners of enclosure keep unit from sliding on your work surface
• Clear 1/8" thick acrylic cover plate prevents damage if an object is accidentally dropped onto your VREF10-002. Since the cover is clear, the power-on LED, on/off switch, and connection terminals are easily seen and accessed.
Recalibration is free for the first two years after purchase- just mail it back to us and for USPS Priority return shipping to destinations within the USA please send a $9.50 PayPal payment to firstname.lastname@example.org. After two years the calibration charge is $12.00 plus shipping. Link to our online store: www.shop.voltagestandard.com
Operation from internal batteries. Optional (disconnected) power supply shown
Operation from external supply