EasySMU (DC2591A) is a programmable-voltage/programmable-current
source from Linear Technology with accurate voltage/current measurement capability. Its primary purpose is to demonstrate a I2C address translator. However, it actually implements a 4 quadrant power supply using LT1970A Power Op Amp, DAC (LTC2655 16 bit) and ADCs (24 bit LTC2485) and some additional circuitry. It even contains a 24LC025 I2C serial EEPROM to store calibration information.

Therefore it is a perfect learning/reference/starting platform for me, even though it is limited to +/-12V and +/-40mA.  I can use it as a preliminary hardware platform while developing parts of the “poor man’s smu” software and display.


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Testing Ian Johnston’s Handheld Precision Digital Voltage Source – PDVS2

I’ve just purchased a PDVS2 from ianjohnston.com. It’s a battery driven precision voltage source based on LM399 (6.95V 0.5 ppm/degC shunt reference) and a 18 bit DAC9881. According to Ian, each shipped unit is: “…assembled & tested in-house, aged/burned-in for 120hrs and calibrated with a HP3458a 8.5 digit multimeter (Keysight Cal. 21/03/18) at constant ambient temp“. It arrived in a solid package that include a power plug (with wire ends) and a calibration card. Note that batteries (2x9V) are not included. As stated on the webpage: “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… These will give you 12-14hrs continuous use between charges.“.

C7D21209I had a hard time finding such batteries in Norway. I did find some, but with only 2-300mAH. I ended up using standard 9V batteries (even if not recommended) for my initial test. Have performed a quick test using Keithley DMM6500 to measure the output. The Keithley had varmed up for 2 hours. The PVDS2 was just turned on (note that warmup period is recommended). The statistics show on the Keithley for each measurement are based on a few seconds data collection (>1000 samples).

Looks to be well within specs ! Note that V2 has improvements over V1. One of the most visible improvements is the added knob.


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