LoadCellShield

Dual INA125 Instrumentation Amplifier Shield

This is a 2-channel Instrumentation Amplifier shield based on the Burr-Brown INA125: http://www.ti.com/product/INA125

The purpose of creating it was to monitor 2 load cells at higher speed than possible with the usual sensors, however it can be used to monitor any bridge-based sensor.

Profile

Usage

The board was designed for flexibility: It can power the Arduino, the Arduino (or compatible) can power it.

U1 offers adequate space for a linear regulator, a DC-DC converter, or a simple jumper in case regulation is not necessary.

Test Points 1..4 and 5..8 are the Vref selection for the two channels.

TP 9..10 and 11..12 allow for either testing the value of RV1 and RV2 gain potentiometers, or for adding a resistor to set a fixed gain, leaving RV1 and RV2 either unpopulated or swapped for trimming.

Digital I/O 2 and 4 control Channel 0 and Channel 1 amplifier enable, allowing power-down modes

Analog output is presented to Arduino A0 and A1.

Operating Advisory

The INA125 can operate at high voltages, and can likewise output high voltages. This design does not currently provide any protection for the Arduino input.

Operating requirements:

• Vin must be higher than the desired Vref.
  • If Vin is higher than the Arduino-compatible can handle, then a regulator or a dual supply must be used.
  • Higher Vref will result in higher output to the Analog Input of the microcontroller
• Maximum possible output from the amplifier must be within the specification for the Arduino Input.

  • Values vary per board, be certain to check.

  • Reference product page linked above for output characteristics

    Tested Configurations (Gain set according to datasheet to be less than max input for boards)

Arduino Uno R3:

• 12V Vin
• Vref 5V
• 3mV/V load cell

Adafruit Metro M4 Express:

• 5V Vin
• Vref 2.5V
• 3mV/V load cell