Circuit Note CN-0216 is a precision weigh scale design using the AD7791 24-bit Sigma-Delta ADC with external ADA4528-1 zero-drift amplifiers. The design features low power consumption, low noise, and high accuracy.
This document presents a precision weigh scale signal conditioning system designed using the AD7791 24-bit Sigma-Delta ADC and external ADA4528-1 zero-drift amplifiers. The circuit is engineered to provide high DC gain with a single supply, utilizing ultralow noise amplifiers at the front end to handle low-level signals from load cells. It achieves 15.3 bit noise-free code resolution for a load cell with a full-scale output of 10 mV. The design allows for flexibility in optimizing the overall transfer function of the sensor-amplifier-converter circuit.
| Noise-Free Code Resolution (System) | 15.3 bit |
|---|---|
| ADC Noise-Free Code Resolution (Device) | 19.5 bit |
| Input Amplifier Noise Density | 5.9 nV/√Hz |
| Output Data Rate Range | 9.5 Hz to 120 Hz |
The design uses the AD7791 24-bit Sigma-Delta ADC along with two external ADA4528-1 zero-drift amplifiers.
The total system achieves a noise-free code resolution of 15.3 bits.
It uses a ratiometric configuration where sense pins are connected to the AD7791 reference inputs to eliminate errors from wire resistance.