The ADX-24 is an USB-powered 8-channel high resolution analog to digital converter.
It is designed for laboratory applications where high measurement resolution is demanded. A noise free resolution of 20 Bit is possible. This equals 1 million steps.

The board also offers 8 digital inputs and 8 digital outputs for lab automation purposes.

The board is USB-powered. The USB section of the circuit-board is completely isolated from the rest of the board to ensure that overvoltage on the inputs (up to 500 Volts) cannot harm the USB-Port of the computer. Ground loops are also eliminated this way.

All connectors on the board are short-circuit-proof. The digital inputs and outputs are overvoltage-proof to ± 30 Volts. The analog inputs of the A/D-Converter can temporarily withstand ± 20 Volts.

You can order the ADX-24 module here.

Technical Specification

Size: 80 x 50 x 15mm, Weight: 25 grams

USB Connector: USB 2.0 Full Speed

Power supplied over USB

Analog to Digital Converter:

  • 24 Bit Resolution
  • 8 Channels
  • Input Ranges:
    • +/- 0.5 Volt
      +/- 1 Volt
      +/- 2 Volt (standard)
      +/- 10 Volt
  • Input Resistance: 1 GΩ    (200 KΩ in 10V range)
  • Input Bandwidth: 1500 Hz    (70 Hz in 10V range)

  • Sampling Rate: Up to 500 Samples/Second
  • Selectable Rates: 0.1 , 1 , 2 , 5 , 10 , 62.5 , 125 , 250 , 500 Samples/Second
    If more than 1 channel is active, the maximum sampling rate over all 8 channels together (sum) is still 500 Samples/Second.
    An alternative firmware version for 4000 Samples/Second is available upon request and free of charge.

  • Resolution:
  • (in the 2 volt range and with 1 active channel)
    At 1 Samples/s: ±3μV = 20 Bit Peak to Peak = 23 Bit effective (RMS)
    At 500 Samples/s: ±10μV = 18 Bit Peak to Peak = 21 Bit effective (RMS)

    (click for larger view)

  • Accuracy:
  • Accuracy without calibration: ±0.1%     (±0.2% in 10V range)
    Accuracy with calibration: ±0.01%     (±0.05% in 10V range)

  • Architecture: Sigma-Delta-ADC (Analog Devices AD7739 with external ADR421 Reference)

Digital Inputs:

  • Perfect for switches, push-buttons and opto-couplers
  • Maximum input voltage: ± 30 V

Digital Outputs:

  • Perfect for relays and opto-couplers
  • Max. current: 400 mA per channel or 800 mA altogether
  • External power supply 5 V to 30 V necessary
  • Short-circuit-proof and over-temperature-protected


Each of the eight analog inputs can make use of a resistive divider to map a +/-10V input signal to the +/-2V range of the AD7739. The divider is made of precision resistors with 0.1% tolerance and only 25ppm/°K temperature drift.

The pins for the digital IOs are positioned on a 2.54mm grid for standard header rows. Thus the module can be easily mounted on custom circuit boards.

A screw terminal row for the analog inputs is part of the package, but not soldered in as default.