CN0357

Overview

The CN0357 plugin for Scopy provides an interface for the CN0357 Electrochemical Gas Concentration Sensor circuit. It enables real-time monitoring of gas concentration by reading the AD7790 16-bit ADC and computing parts-per-million (ppm) values based on configurable sensor parameters and feedback resistance.

CN0357

Features

  • Gas Concentration Measurement: Real-time ppm calculation from ADC readings.

  • Configurable ADC Sampling: Adjustable update rate from 16 Hz to 120 Hz.

  • Dual Feedback Modes: Supports both a digital potentiometer (rheostat) and a fixed resistor for transimpedance feedback.

  • Sensor Calibration: Adjustable sensor sensitivity and computed conversion coefficients.

Supported Devices

  • CN0357 (Electrochemical Gas Concentration Sensor using AD7790 ADC and AD5270 Digital Potentiometer)

Getting Started

Prerequisites

  • A CN0357 evaluation board connected to a supported FPGA carrier

  • Scopy version 2.3.0 or later

Using the Plugin

Connect the CN0357 board to the host system and add the device in Scopy. The plugin automatically discovers the AD7790 ADC and, if present, the AD5270 digital potentiometer. Once connected, the System section begins polling the ADC and displaying live measurements.

Description

The CN0357 view is divided in three sections:

  • ADC Settings

  • Feedback Settings

  • System

ADC Settings

  • Update Rate (Hz): Selects the ADC sampling frequency. Available options are 120, 100, 60, 50, 25 and 16 Hz.

Feedback Settings

  • Feedback Type: Selects the feedback configuration for the transimpedance amplifier. In Rheostat mode the AD5270 digital potentiometer sets the feedback resistance. In Fixed Resistor mode a user-specified constant value is used instead.

  • RDAC Value: Sets the digital potentiometer code (0 to 1023). Only active in Rheostat mode. The corresponding resistance is computed and displayed in the System section.

  • Program Rheostat: Writes the current RDAC value to the AD5270 digital potentiometer hardware.

  • Fixed Resistor: Sets a constant feedback resistance value in ohms. Only visible when Fixed Resistor mode is selected.

System

The System section displays real-time measurements and derived calibration data in a two-column layout.

Measurements

  • Concentration (ppm): Computed gas concentration based on the sensor voltage, feedback resistance and sensor sensitivity.

  • Conversion (mV): ADC voltage reading from the electrochemical sensor, converted from raw counts to millivolts.

  • Supply Voltage (V): ADC supply voltage reading, converted from raw counts to volts.

Data

  • Sensor Sensitivity (nA/ppm): Calibration parameter for the electrochemical sensor. Adjustable from 1 to 100, with a default of 65.

  • Feedback Resistance: Computed feedback resistance in ohms, derived from the selected feedback mode and its parameters.

  • ppm/mV: Computed conversion coefficient representing parts-per-million per millivolt.

  • mV/ppm: Computed conversion coefficient representing millivolts per part-per-million.