Reference design for a fully isolated, low‑power pH sensor signal conditioner and digitizer with automatic temperature compensation.
The CN‑0326 reference circuit provides a completely isolated, low‑power pH sensor signal conditioner and digitizer. It uses the AD7793 24‑bit Σ‑Δ ADC, AD8603 precision CMOS op‑amp, and ADuM5401 digital isolator to achieve high‑precision measurements with automatic temperature compensation.
The design includes an evaluation board (EVAL‑CN0326‑PMDZ), a system demonstration platform (EVAL‑SDP‑CB1Z) and a PMOD adapter. Detailed calibration procedures, noise analysis, and software support are described, allowing users to integrate the circuit into industrial applications such as water treatment and chemical processing.
| Measurement range | pH 0 to 14 |
|---|---|
| Zero‑point pH | pH 7.00 ± 0.25 |
| Accuracy | ±0.05 pH |
| Resolution | 0.01 pH (0.1 mV) |
| Temperature range for accuracy | 20 °C to 25 °C |
| Maximum operating temperature | 80 °C |
| Response time | ≤ 1 s to reach 95 % of final value |
| ADC noise‑free resolution | greater than 14 bits |
It can measure pH values from 0 to 14.
The circuit achieves an accuracy of ±0.05 pH.
The AD7793 ADC provides more than 14 bits of noise‑free resolution.
Accurate measurement is supported between 20 °C and 25 °C.