QA350 Microvolt DC Volt Meter [Retired]

QA350 Microvolt DC Volt Meter [Retired]

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This product was first introduced in 2016, and has since been retired and is no longer for sale. The QA350 has been replaced by the QA351

Every lab needs a high-resolution logging DVM. The QA350's fully isolated design allows low-noise DC measurements in a variety of settings, including chemistry, semiconductor development, battery development and high-accuracy sensor verification. 

The QA350 relies on a built-in reference to calibrate the ratio between the hi and low ranges. If you have a preferred lab reference, you may use that it to improve the QA350 accuracy beyond the indicated +/- 400 PPM. For example, various vendors on eBay can provide calibrated +/-30 PPM 5 or 10V voltage references that can be used to set the ultimate accuracy of the QA350 to under 50 PPM at room temperature.  

The core of the QA350 is a TI ADS1256 24-bit ADC, capable of delivering 23-bits of noise-free resolution. The ADS1256 reference is provided by a very high quality MAX6126A 2.048V reference rated at +/- 200 PPM.

Important note: The QA350 is NOT for use on high-energy circuits or circuits directly connected to the mains. It is rated as CAT I, which is the "weakest" safety category rating. DO NOT USE THE QA350 ON CIRCUITS THAT ARE POTENTIALLY HAZARDOUS OR LETHAL. It is meant for measuring ultra precision transducers, DACs, opamps and any other circuit where you need precision.


  • Isolated and fully differential (max offset from PC ground is +/- 100V. Tested to >10G ohm at 1000V input ground to chassis ground)
  • 1M ohm input impedance. Input resistance drops 1-3% at higher sample rates.
  • Up to +/-50V peak input
  • Low Range: +/- 5V (~1uV resolution)
  • Hi Range: +/-50V (~10uV resolution)


  • Accuracy @ Calibration Temp: +/- 400 PPM = +/- 0.04%
  • System Tempco: +/-50 PPM (+/-3 degrees C from calibration temp)
  • 2.5 measurements per second (slow)/1000 measurements per second (fast)
  • Rejection of 50Hz/60Hz through digital filtering at slow sample rate
  • Logging to file (1000 measurements per second)
  • True RMS measurements added in release  1.70  (F3db = 4.8 KHz)


  • MAX6126A 4.096V reference (+/-200 PPM, 3 PPM/C tempco) for ADC reference
  • Additional MAX6126A 2.5V reference (+/- 200 PPM, 3 PPM/C tempco) output on front panel for DVM check, high/low gain range calibration, etc


  • Supports automation via DotNet Remoting. It's very easy to write a VB or C# app to programmatically gather readings from the QA350. 
  • Open source, both firmware and PC software. See the sources for both on GitHub

The QuickStart guide is located here.

Using the QA350 to characterize LDOs is here.

Blog post on True RMS addtion is here