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Handheld Precision Digital Voltage Source - PDVS2

A handheld Precision Digital Voltage Source, true 0.0000V to 10.0000Vdc range, battery powered.

Total Price: £287.50
Price excl. VAT (EU only): £287.50
VAT (EU only):
Price / kg:

Model: PDVS2 (new for 2017)
Handmade in Great Britain by Ian Johnston

OUT OF STOCK! - Please use the NOTIFY ME link above and you'll get an email immediately stock is available again.

Update 7th August: Currently in production, should be available in about 5 weeks.

Unlike anything else on the market this is a truly handheld Precision Digital Voltage Source. With a user adjustable range from a true 0V to 10Vdc and an accuracy/stability down in the uV’s it has a multitude of uses as a calibrator, reference & precision voltage source.

New for 2017, this is version 2 and offers the following key features & changes over the original.

  • True zero volts output. Range: 0.0000 Vdc to 10.0000 Vdc.
  • Higher resolution 2nd mode, 0.01000 Vdc to 2.00000 Vdc in 10 uV steps.
  • Rotary shaft encoder for quick and easy output adjustment.
  • USB port for remote operation & monitoring of the unit via a Windows PC app.
  • On-board charging pcb/socket added for Li-ion batteries (DC adaptor & batteries req'd).
  • LED backlighting.
  • Extension PCB fitted on the back of the banana sockets to facilitate a better mechanical layout, also contains components to clean up the final output.
  • New upgraded Atmel Microcontroller (ATMEGA1284).
  • Software optimized and cleaned-up including faster boot & easier software calibration.
  • RAMP mode, similar to the PLAYBACK mode but allowing ramp up/down (linear) of the output voltage.
  • CE approved.

Here's a link to the project page (PDVS1) containing some tempco tests and other design data, and a link direct to a comparison to other available portable voltage references here.


EEVBLOG Starts The Ball Rolling:-
Many thanks to Dave Jones over at the EEVBlog for including an early Version 1 prototype in his Monday Mailbag (I sent him one unannounced!), it looked like it was greatly received! Link to his video here .
So, with the ball rolling I pushed forward with the design even further and have made many improvements over the prototype that Dave Jones saw, as follows:-
Better stability, Less noise on output, Better quality banana sockets, More intuitive user interface, Internal sense line to banana's allowing heavier loads without compromising output voltage accuracy, Coax ditched in favour of heavy gauge wire, MAX6350 Vref ditched in favour of an LM399AH (much better stability and tempco).

Martin Lorton Confirms Hard Work Has Paid Off:-
So, with the new Version 1 unit in production I sent one over to Martin Lorton where he turned out a great independant review of  the unit, link to his video here.
But it didn't stop there because not long after in another video Martin used the Voltage Source to help him repair his own HP3458a 8.5 digit multimeter!, see the video here.
Update: Prompted by Martin, I now have my own HP3458a that I use for testing & calibration of all production units.


- True 0 Vdc to 10 Vdc user adjustable output in 10 V mode (4d.p’s effective, 38.146uV).
- A 2nd mode offering 0.01 Vdc to 2.0 Vdc user adjustable output (5d.p’s effective, 10 uV).
- Voltage setting or ramp up/down controls via the 12 button numeric keypad.
- Digital Rotary Encoder (potentiometer) allowing quick, on the fly adjustments of the output voltage.
- LED backlighting (user adjustable & auto-limited).
- Soft power switch.
- Based on the industry standard LM399AH (0.5 ppm/degC) voltage reference.
- All digital calibration, no internal potentiometers.
- 18bit DAC with an accuracy/stability down in the uV’s (using a PLC filter of 1.0 or higher).
- Battery voltage monitor, including low voltage warning, auto-shutdown and charging status.
- Output voltage monitor including overload / short circuit protection.
- 3” Graphics Monochrome LCD (128x64 pixels).
- Atmel Atmega1284 micro-controller (uses Arduino bootloader).
- Precision chopper op-amp on final output with extra stability achieved using low tempco resistors.
- Re-calibration by the user possible via keypad/LCD and saved to flash rom.
- On-board charging added for Li-ion batteries using a battery management IC. Important: Batteries and DC adaptor are not supplied.
- Battery reverse polarity protection.
- Quality Hammond 1599 case, aluminium anodized & engraved front panel & 4mm banana sockets.
- Printed manual including factory calibration/settings test record supplied. Unique serial number.
- Software function- PLAYBACK mode.
- Software function- RAMP mode.
- Software function- Remote Operation via Windows app (via new USB port). Important: Mini USB cable not supplied.

Prior to shipping each unit:
- Assembled & tested all in-house. LM399AH aged/burned-in for 48hrs in unit, including numerous power cycles. Calibrated against an HP3458a 8.5 digit multimeter. Calibrated at approx. 23degC ambient. Packed in a double wall box.

What you get in the box:
- 1off PDVS2 (no batteries, no charger), 1off Charging connector c/w tail, a Calibration record, a CE Declaration of Conformity and details of the PDF manual & Windows app downloads.


- Voltage reference IC = LM399AH (0.5 - 1 ppm/degC temperature coefficient).
- 10 V mode = 0.0000 Vdc to 10.0000 Vdc in 38.146 uV steps.
- 2 V mode = 0.01 Vdc to 2.00000 Vdc in 10uV steps.
- Load = 3kohm minimum. Example: At 10Vdc output with 3kohm load = 3.3mA (whilst maintaining output within approx. 10uV).
- Accuracy = 0.001% (within 100uV & using a PLC filter of 1.0 or higher).
- Stability = 0.0001Vdc variation max. 4d.p. mode.  Stability = 0.00004Vdc typical variation in extended 5d.p. mode.  Drift (long term) = This has not been characterized. Orientation of the unit may effect output. Units are calibrated horizontally.
- Temperature coefficient = Less than 1 ppm/degC (tested across a temperature variation of 11.5degC - See project page here for more info).
- Stabilization time = typically 10mins when stored at approx. 23degC. Can be quicker depending on ambient and storage conditions.
- Output short circuit = indefinite (20mA).
- Power Source (batteries) = Two Lithium-Ion re-chargeable 9V PP3 batteries (Not supplied, 600mAh batteries recommended).
- Power Source (external power)  = 18 to 24Vdc input (also charges the batteries) @ 400mA min recommended.
- Battery = Approx. 12hrs (EBL 600mAh re-chargeable batteries) typical continuous operation with backlighting off.
- Current drain = 50mA approx. (after 10mins)
- Dimensions = 158mm x 83mm x 35mm (case size).

See the PDVS2 Manual below for instructions on how to upgrade, or contact me.
- PDVS2 Unit - V2.03 (May 2017). Changelog: Added battery voltage & charge current to the menu screen, Rotary Encoder can be disabled, Battery Charge Enable Status now saved to EEprom.
- PDVS2 Windows App - V1.2 (02/06/17) for V2.02 & V2.03 firmware units - Download here. Changelog: Better compatibility with non-English versions of Windows.
- PDVS2 Manual - V1.2 (27/04/17) for V2.02 firmware units - Download here.
- PDVS2 Manual - V1.3 (13/05/17) for V2.03 firmware units - Download here.

The user can re-calibrate the PDVS2 via the software menu, however, for those that don't have a reference standard to gauge against we offer a return to base recalibration of the PDVS2, the user just needs to pay the shipping in both directions and the service is free.

Batteries are not supplied so customers must supply their own and we highly recommend 600mAH or better Li-ion PP3 batteries from EBC or Etinesan (I did a battery test here ). These will give you 12-14hrs continous use between charges.
A DC adaptor or power supply is required (not supplied) to charge the batteries and should be rated at 18V - 25Vdc @ 0.4A. A compatible plug with tails is supplied.
Only batteries in a similar state of charge should be fitted together.
Is the charging safe? - We've all seen the issues with phones lately, so I have implemented a well know current-limited, switch-mode Li+ charger/controller and am running it quite low (0.25A charge current - 2.5hrs approx.) to avoid any issues. The software also monitors the charge current and can shut it down.
Finally, the batteries I recommend have protection circuitry built in as an added layer of protection for under-voltage and over-charging.
Note: If the unit is operated whilst charging (via the DC input) additional noise may be incurred on the final output. This is a precision instrument and is designed primarily to be used on batteries.


The V2 unit is visually pretty close to the previous version except of course for the rotary encoder, the USB port and the charging port visible on the side.

PDVS2 1a

Internal view of the new unit. A brand new V2.0 pcb which includes a new, bigger, processor. A new banana plug adaptor board.
A DC adaptor jack next to the batteries to power the unit from an external source and/or charge the batteries. You can see the charger Pcb under where the batteries sit.

PDVS2 16a

The banana adaptor pcb. This tidies up the interface from the main Pcb to the banana sockets. The 3 connections are voltage out, 0Vdc and a v.sense line. In this photo you can also see the backlighing module (white) under the LCD.

PDVS2 13a

Naked view of the pcb's top side. Here you can see the battery charging circuit below keyboard (not shown) and well out of the way of the main pcb. You can also see the rotary shaft encoder and on/off switch below the Lcd.

PDVS2 14a

Naked view of the pcb's bottom side. The LM399AH voltage reference (large white package) stands out and the PP3 battery terminals. At the top of the photo you can see the mini Usb connector and the DC power connector. Over to the left is the Atmega1284 uController.

PDVS2 12a

Screenshots (subject to change relative to firmware updates): The main menu screen. You can also see the backlighting in operation.

PDVS2 2a

Main screen - 10v mode.

PDVS2 4a

Main screen - 2v mode. The 5th DP is now full size as 10uV resolution is attainable in this mode.

PDVS2 7a

PDVS2 5a

PDVS2 6a

PDVS2 18

PDVS2 17

PLAYBACK mode running.

PDVS2 19

RAMP mode running.

PDVS2 20

Windows app:



 USER PHOTOS (please send in yours if you want them featured here)

Mauri from Finland purchased a PDVS2 in April 2017:

PDVS2 Mauri_34401a thumb PDVS2 Mauri ebd a20h thumb PDVS2 Mauri ut181a

Joe from the USA purchased a PDVS2 in April 2017:

20170531 144655 20170531 144746