In the blogs "How to Use a Gas Sensor (Analog Output Part ①)" and "How to Use a Gas Sensor (Analog Output Part ②)" we explained how to log the output of FIGARO's semiconductor-type gas sensors in a typical office environment using an evaluation module (EM26).

In this article, we will explain how to acquire analog output from gas sensors in gases after injecting a gas into the evaluation chamber using three types of FIGARO's semiconductor-type gas sensors and an evaluation module.

How to Acquire Data in a Gas Environment

Required Equipment

This section explains how to acquire analog output data during the exposure to gases for evaluation of gas sensors. For this evaluation, the following equipment will be used:

Features of the Evaluation Chamber (EC01)

The evaluation chamber (EC01) is a compact and user-friendly evaluation device designed for performance evaluation and characteristic verification of gas sensors. Gas sensors exhibit different response characteristics depending on the type and concentration of gas.

Therefore, to properly verify sensor characteristics, a stable evaluation environment under controlled conditions is required. EC01 is widely used as a tool that enables proper sensor evaluations in a simplified manner.

By using this chamber, it is possible to easily control test conditions with a specific gas concentration and measure the sensor's response and gas sensitivity. Since multiple sensors can be evaluated under the same conditions, EC01 plays an important role in the development of gas sensor application products, sensor selection, and quality control.

Names of the Parts of the Evaluation Chamber (EC01)

1. Test chamber body
2. Control box
3.  AC power supply
4. Power switch
5. Stirring fan switch
6. Stirring fan
7.  Power supply cable
8. Flat cable for sensor output
9. Chamber lid (Photo shows a lid with gas inlet and outlet ports)
10. Gas injection port

Mounting Gas Sensors and Cable Connections

This time, we will use the following three types of semiconductor-type gas sensors from FIGARO Engineering:

• TGS2600 (gas sensor for detecting air contamination)
• TGS2602 (gas sensor for detecting air contamination and odors)
• TGS2603 (gas sensor for detecting air contamination and offensive odors)

Now, let's briefly outline the steps for mounting gas sensors and connecting cables.

(1) Mount the gas sensor onto the evaluation module (EM26).

(2) Attach the evaluation module (EM26) with the gas sensor mounted in Step (1) to the module measurement board included with the evaluation chamber (EC01).

(3) Connect the 50-core flat cable extending from the evaluation chamber (EC01) to the data logger.

Wiring is now complete. For more details on mounting the gas sensors and connecting cables, please refer to "How to Use a Gas Sensor (Analog Output Part ②) - Acquiring Data Using an Evaluation Chamber -."

Data Acquisition

To acquire data during exposure to gas, prepare the "5 ml syringe" included with the evaluation chamber (EC01) along with the test gas. Also, to ensure proper gas exhaust, place the evaluation chamber inside a local exhaust system or fume hood.

Now, let's briefly outline the steps for data acquisition.

(1) Plug the AC power cable of the evaluation chamber (EC01) into an outlet.

(2) Turn on the main power switch of EC01.

(3) Turn on the data logger and set the sampling conditions.

(4) Close the chamber lid.

(5) Start logging with the data logger.

(6) The analog output from the gas sensors will be recorded in the data logger.

(7) Prepare the test gas. To inject the gas as accurately as possible, purge the syringe before taking gas (*1).

*1: Purging means taking the test gas 2-3 times beforehand to expel the small amount of air remained in the syringe and replace the inside with the test gas.

(8) Taking the test gas. Draw the gas of the calculated volume into the syringe to achieve the target test gas concentration. (*2).
Gaseous sample (e.g., hydrogen (H2)) or liquid sample (e.g., ethanol) to be evaporated can be used as a test gas.

*2: For details on how to calculate the gas sample volume, refer to the EC01 Instruction Manual.

(9) Insert the syringe needle through the rubber gas injection port on the chamber lid and inject the gas (left image). Immediately after that, turn on the built-in stirring fan (right image). The stirring fan helps quickly homogenize the gas concentration.

Inject the gas through the mending tape that prevents the rubber injection port from popping out.

(10) Once the necessary data has been acquired, exhaust the gas from inside the chamber. Ensure safe gas exhaust outdoors using a fume hood or a local exhaust system.

(11) When logging is stopped, the data is saved.

*For information on how to use the data logger, please refer to "How to Use a Gas Sensor (Analog Output Part ①)" and "How to Use a Gas Sensor (Analog Output Part ②)."

Graphic Display of Analog Output Dat

The graph below shows the CSV data acquired, plotted using Microsoft Excel. The responses of the three types of semiconductor-type gas sensors in a hydrogen gas can be clearly observed.

If you wish to monitor extremely small gas leaks or ambient gas concentrations, we recommend using gas detectors such as the XP-3000 II series or the fixed-type PS-8 series (both made by New Cosmos Electric).

Let's Make Use of the Gas Sensor

There are several ways to acquire analog output data from gas sensors, and the suitable method varies depending on the type of sensor and its intended application (e.g., evaluation, IoT integration, or control).

On FIGARO Engineering's official website, you can find easy-to-understand animations that explain the detection principles and usage of gas sensors--please make use of these resources.

Learn About Gas Sensors Through Videos