Description

This is a new Feather compatible board for reading precision analog sensors like load cells, thermocouples, and strain gauges. It uses the AD7124-4, a 4 channel, 24 bit, differential ADC (Can also be configured as 7 single ended channels). Like the 6 Channel 24 bit Featherwing this board is designed for lower power, monitoring type applications, however it can also be configured for significantly higher sampling rates than the AD7794. The board also includes a low pass anti-aliasing filter on the inputs, a 5th input pin for a shield wire connection, and software enabled excitation voltage without using an additional pin.

Each channel can be configured independently so you can mix sensor types as needed. The library includes an example application with one load cell, two thermocouples, and two potentiometers. The two potentiometers are read as a single ended voltage allowing for 5 sensors total. The NHB AD7124 Analog Sensor FeatherWing can easily read full bridge sensors, thermocouples, and potentiometers with no additional components. 1/4-bridge strain gauges can be read by adding external bridge completion resistors. The maximum input voltage is 3.3V though, so please be careful!

Specifications

• RMS noise down to 23 nV at 9.4 SPS
• Low power operation with 3 conversion power modes
• Power-down current of 5 μA maximum (AD7124 chip)
• Low noise, programmable gain instrumentation amplifier (1 to 128)
• Band gap reference with 10 ppm/°C drift typical
• Simultaneous 50 Hz/60 Hz rejection at 25 SPS
• Update rate: Up to 19200 sps (per datasheet for single channel)
• 4 differential analog inputs, (or 7 single ended)
• Independent configuration of each channel
• Low pass anti-aliasing filter on inputs
• 5 pin connections with excitation, ground, and shield for each channel
• Shield can be tied to chassis or to ground (trace jumper on bottom)
• On board 2.5v LDO controlled in software without needing additional pin
• Software enabled bias voltage on all channels (for reading thermocouples)

The board is available with screw terminals or pin headers for the sensor connections. All terminals and headers are sold unsoldered by default.

Library Installation

The library can be installed from the Arduino library manager, just search for "NHB_AD7124". Alternatively you can manually install by cloning the git repo linked to below.

A MicroPython library is also now available here

And a CircuitPython libray is available here