Handheld Precision Digital Voltage Source - PDVS2mini 20bit

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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

The PDVS2mini 20bit gives a true 0.00000 to 10.00000Vdc in 10uV steps using a 20bit DAC.
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.

INTRO:

Built on the success of the PDVS2 I figured I would attempt to make a more affordable version but with a higher resolution & performance. It supports dual Lithium-Ion batteries c/w charging circuit, 4mm banana sockets and a graphics LCD. It uses a MAX5719A which is a 20bit DAC. I've called this new product the PDVS2mini.

FUNCTIONS & FEATURES:

  • 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.

SPECIFICATION SUMMARY:

  • 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 & laser cut parts.


MANUAL, DOWNLOADS & FIRMWARE:

  • PDVS2mini 20bit Firmware - V1.02 (September 2019) is shipped with all units.
  • PDVS2mini 20bit Manual - Version 1.0 - here.
  • Windows PC download here.


RE-CALIBRATION:

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).
Alternatively, you can send your unit back to us for free re-calibration (you just pay the shipping), information here.


IMPORTANT NOTE ABOUT BATTERIES & CHARGING:

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.

PRODUCT REVIEWS (BY OTHERS):

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.


CUSTOMER COMMENTS:

From Mike in Sweden (Oct. 2019)
"What a great little device you have made! I was impressed by the quality of the PCB and how well put together it is. The soldering is perfect, with all components nicely placed and with perfect fillets on every soldered connection.
I've been doing some testing today with a couple of my good quality meters and my Solartron 7150+ confirmed the accuracy of the device and your calibration. I know my 7150+ reads about 100uV too high, so the readings below are absolutely spot on.

Set Voltage       7150+ (5 digit mode)        From Calibration Sheet
0V =                 0.000001                           0.000000
1V =                 1.00001                             1.000006
2V =                 2.00001                             1.999999
3V =                 3.0000                               3.000003
4V =                 4.0001                               3.999998
5V =                 5.0000                               4.999996
6V =                 6.0000                               5.999996
7V =                 7.0001                               7.000001
8V =                 8.0001                               7.999996
9V =                 9.0002                               9.000003
10V =               10.0002                             9.999999

Great stuff! I'm a very pleased customer and thank you for making this device available with such precision for a humane price. I hope you sell lots of them."


PHOTOS:

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.

Graph1

 
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.

Graph4

 

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.
Notes:
Conditions not ideal, i.e. LED lighting, busy electronics workshop.......but it is typical.
Peaks removed (lights switched on/off).

Graph5b