Handheld Precision Digital Voltage Source - PDVS2mini 20bit

A handheld Precision Digital Voltage Source, true 0.00000V to 10.00000Vdc range, battery powered.
Total Price: £220.00
Price excl. VAT (EU only): £220.00
VAT (EU only):
Price / kg:

Model: PDVS2mini 20bit
Handmade in Great Britain by Ian Johnston
NEW FOR 2019, THE PDVS2mini 20bit GIVES A TRUE 0.00000 TO 10.00000Vdc IN 10uV STEPS USING A NEW 20bit DAC.
UPDATE 11th Oct. 2019 - Units are all under soak test, calibration starting soon
Final price subject to change.

A smaller, more affordable sister product to the PDVS2, 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.


Built on the success of the PDVS2 I figured I would attempt to make a more affordable version but with certain criteria & functionality retained:- Dual Lithium-Ion batteries c/w charging circuit, 4mm banana sockets and a graphics LCD. It uses a MAX5719A which is a 20bit DAC and has a higher resolution than used in the PDVS2 (but a higher INL - Intergral Non-Linearity where lower is better). I've called this new product the PDVS2mini.


  • True 0 Vdc to 10 Vdc user adjustable output (5d.p’s, approx. 10uV steps)
  • Voltage setting via up/down pcb pushbuttons
  • Soft power switch
  • Based on the industry standard LM399AH (0.5 ppm/degC) voltage reference
  • All digital calibration, no internal potentiometers
  • 20bit 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 short circuit protection
  • 2.4” 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, and saved to flash rom
  • Charging pcb/socket for Li-ion batteries using a battery management IC. Batteries and DC adaptor are not supplied
  • Battery reverse polarity protection
  • ABS Hammond enclosure
  • Manual including factory calibration/settings test record. Unique serial number
  • CE approved

Prior to shipping each unit assembled & tested in-house, aged/burned-in for 120hrs and calibrated with a HP3458a 8.5 digit multimeter (Keysight Cal. 08/03/19) at constant ambient temp.
In the box - 1off PDVS2mini (no batteries, no charger) in an ESD bag, 1off Charging connector c/w tail, Calibration record and details of the PDF Manual (c/w CE Declaration of Conformity).

NOTICE: VAT registered EU companies please contact me prior to purchase to receive instructions on how to zero rate the VAT.


  • Voltage reference = Uses an LM399AH (0.5 - 1 ppm/degC temperature coefficient)
  • 0.00000 Vdc to 10.00000 Vdc in 10 uV (0.00001 Vdc) steps
  • Load = 3kohm minimum. Example: At 10Vdc output with 3kohm load = 3.3mA (whilst maintaining output within approx. 10uV)
  • Accuracy = Within 100uV. Typically 0.001% at 10V output
  • Stability = 0.0001Vdc typical variation. Orientation of the unit may effect output (calibrated horizontally), as will powering from external DC
  • Temperature coefficient (unit) = Typically < 3 ppm across a 10degC temperature change (see graph below of tempco test)
  • Drift (12 months typical) = tba - SPEC TO BE CONFIRMED
  • Stabilization time = 10mins to 1hr depending on ambient temperature, coming off battery charge and last use
  • Output short circuit = indefinite (20mA)
  • Power (batteries) = Two Lithium-Ion re-chargeable 9V PP3 batteries (Not supplied, 600mAh batteries recommended)
  • Power (external power)  = 18 to 24Vdc input (also charges the batteries) @ 400mA min recommended
  • Battery consumption = 100mA approx. at power up, reducing to 50mA approx. when LM399AH heater has stabilized (a few minutes)
  • Battery quiescent current (unit switched off) = 4uA approx.
  • Battery = Approx. 12hrs (EBL 600mAh re-chargeable batteries) typical continuous operation
  • Dimensions = 106mm x 66mm x 47mm
  • Contains 3D printed parts.


  • PDVS2mini 20bit Firmware - V1.01 (August 2019) is shipped with all units.
  • PDVS2mini 20bit Manual - Version 1.0 - here.


The user can re-calibrate the PDVS2mini 20bit via the Calibration menu. The PDVS2mini 20bit uses multi-setpoint X-Y calibration (rather than simple Zero & FSD) in order to help reduce DAC INL (Integral nonlinearity).


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.
Is the charging safe? - I have implemented a current-limited, switch-mode Li+ charger/controller and am running it quite low (0.25A charge current) to avoid any issues. The software also monitors the charge current and can shut it down.
The batteries I recommend have protection circuitry built in as an added layer of protection for under-voltage and over-charging.
Important: The PDVS2mini 20bit is optimized and primarily designed for battery operation, the calibration & stability of the PDVS2mini 20bit is only supported under battery usage. External DC adaptors/PSU's (not supplied) through common mode noise may inhibit accuracy. After a lengthy charging session it is advised to let the PDVS2mini recover (30 - 60mins) in terms of internal heat being generated and any subsequent tempco offset as a result.


In August 2019 I sent 3 prototype units out to a variety of users in order to gauge response and obtain feedback of both the hardware & software. This proved invaluable as a major software bug was found (and fixed!).
- TiN of volt-nut fame over at XDEVS.COM has done some TEMPCO testing of the PDVS2mini and has published his results including photos here.
- Steve Gardner has published a YouTube review here.
- The DefPom has published a YouTube review here.


Standard 4mm banana sockets (19mm apart).
1 soft power pushbutton & 5 others for navigating the menus and selecting of the digits for changing the output voltage.
2.4" graphics LCD.
Battery charge socket.

PDVS2mini 13

106mm x 66mm x 33mm Hammond enclosure.
4 screws allow access to the internals/batteries.

PDVS2mini 15

Batteries are easily inserted into their plastic holders.

PDVS2mini 2

Uses the same microcontroller, charging circuit and DC power circuit as the PDVS2, albeit there's a new 20bit DAC IC.
Shown here is the underside of the PCB with some of the electronic components and the battery holders.

PDVS2mini 3

The DC input and battery charge Pcb is mounted at right angles to the main Pcb.

PDVS2mini 6


Here are a couple of graphs where I did some data logging & tests.
Yellow = 3458A logging (primary DMM)
Aqua = 34461A logging (just for fun)
Red = Temperature degC
Green = %RH

General logging test of the output (set to 10Vdc), both on & off charge, stability overnight etc. Note how much more stable the 3458A is compared to the 34461A.


Practical example - Varying temperature between 14 and 34degC (24 nominal) in an environment chamber and recording the output voltage:
Initial value = 9.9999982 Vdc @ 24degC
Max recorded = 10.0000280 Vdc @ 34degC
Min recorded = 9.9999642 Vdc @ 14degC
Yellow = 3458A logging (primary DMM)
Red = Temperature degC
Green = %RH
White = Calculated ppm variation
Results = Typically < 3 ppm variation across a 10degC temperature change, or a tempco average of 0.3ppm/degC.



30 minute noise test, logging interval 5 secs, NPLC 100. PDVS2mini running on batteries, set to 10.00000 Vdc.
Yellow = 3458A logging (primary DMM)
Red = Temperature degC
Green = %RH
Aqua = Max/Min data taken.
Conditions not ideal, i.e. LED lighting, busy electronics workshop.......but it is typical.
Peaks removed (lights switched on/off).