Reference Design: Low Noise, Single-Supply, Toxic Gas Detector, Using an Electrochemical Sensor with Programmable Gain TIA for Rapid Prototyping

The EVAL-CN0357-PMDZ is a Pmod interface board with a single-supply, low noise, portable gas detector, using an electrochemical sensor.  Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of many toxic gases. Most sensors are gas specific and have usable resolutions under one part per million (ppm) of gas concentration. This board uses the ADA4528-2, dual auto zero amplifier, which has a maximum offset voltage of 2.5 μV at room temperature and an industry leading 5.6 μV/√Hz of voltage noise density. In addition, the AD5270-20 programmable rheostat is used rather than a fixed transimpedance resistor, allowing for rapid prototyping of different gas sensor systems, without changing the bill of materials.

Block Diagram:

Features:

• Complete electrochemical sensor

• Low power

• Single Supply

Applications:

• Precision instrumentation

• Medical instrumentation

• Handheld test equipment

• Monitoring

Functional Setup

The following equipment is needed for evaluating the CN-0357 circuit:

• PC with USB port and Windows® XP, or Windows Vista (32-bit), or Windows 7 (32-bit)

• EVAL-CN0357-PMDZ evaluation board

• PMD-SDP-IB1Z interposer Board

• EVAL-SDP-CB1Z controller board

• CN-0357 Evaluation Software

• Calibration gas (less than 250 ppm)

• EVAL-CFTL-6V-PWRZ or equivalent 6 VDC power supply

Compatible Boards:

• Intel boards with the Pmod connector 

• EVAL-SDP-CB1Z: Blackfin® (SDP-B) controller board

• SDP-PMD-IB1Z: Pmod to SDP Adaptor Board

Related ADI parts:

• ADA4528-2: Precision, Ultralow Noise, RRIO, Zero-Drift Dual Op Amp

• AD5270: 1024-Position, 1% Resistor Tolerance Error, SPI Interface and 50-TP Memory Digital Rheostat

• ADR3412: Micro-Power, High-Accuracy 1.2V Voltage Reference

• AD8500: Micropower Precision CMOS Operational Amplifier

• AD7790: 16-Bit, Single-Channel, Ultra Low Power, Sigma Delta A/D Converter

Reference Documentation:

• ADI Pmod Daughter Cards