EM26AQS - Evaluation Module for TGS26 Series
Air Quality Sensors

Instruction ManualTable of Contents
1. Overview
2. Functions and Settings of Each Part2-1) Pin Connections
2-2) Switch setting for Power input2-3) Switch settings for gas sensor models
2-4) Reset function2-5) Air quality level output and LED indication2-6) Load resistance RL setting2-7) Notes about sensor output (VOUT)
3. How to use EM26AQS
3-1) Warm-up period3-2) Normal operation mode3-3) Reset function3-4) Sensor mounting
4. Specifications
5. Extension Function5-1) Setting the TGS2660 mode
5-2) Ventilation Index Output and LED Indication5-3) Operation in TGS2660 mode
6. Dedicated PC Application
6-1) Acquisition of the dedicated application software package
6-2) Installation method for USB drivers
6-3) Launching and operating the dedicated application
6-4) Setting various parameters6-5) Reset function
7. Troubleshooting1. Overview
The EM26AQS is a multifunctional evaluation module with built-in signal processing software for thedynamic benchmark renewal algorithm, which is required when incorporating semiconductor-type airquality gas sensors (TGS2600, 2602, 2603) into air purifiers, among other applications.
The module carries out signal processing on the voltage output of the gas sensor to output the Indoor
Air Quality Level (VAQL) as a voltage with 5 levels. Furthermore, the degree of indoor air pollution canbe monitored visually by 5 LEDs of different colors which correspond to the air quality levels (VAQL).

2. Functions and Settings of Each Part

Power input switching: SW1
Sensor socket:GS1

Load resistance RL setting:
JP1 to JP3
CN1LEDs: D1 to D5

CN3

Reset switch: SW3

Target sensor setting: SW2

Fig 1. Name of each part2-1) Pin Connections: CN1
Pin No. (※1)

NameDescription

1

VIN

Circuit voltage

2

VOUT

3

VAQL/VIO

4

NCSensor output
Indoor air quality level output/ Ventilation
Index Output(※2)
No connection

5

GNDGround※1 Suggested female connectors for mating with the 5-pin connector (JST:MB5P-90S):
JST: XHP-5P or 05JQ-BT※2 For the Ventilation Index Output (VIO), please refer to "5. Extension Functions (TGS2660)".

22-2) Switch setting for Power input: SW1
There are two connectors available for the power input: a 5-pin connector or a USB-Type C connector.
When using the 5-pin connector (CN1), switch SW1 to the "CN1_ON" side. When using the USBType C connector (CN3), switch SW1 to the "CN3_ON" side.
By connecting the USB Type-C connector to a PC with a cable, measurement data can be displayedon a computer monitor in real time. For details, please refer to "6. Dedicated PC Application."2-3) Switch settings for gas sensor models: SW2
Before turning on the power, set the DIP switch according to the gas sensor to be evaluated. Both
SW2-1 and SW2-2 are set to OFF at the factory.
* The DIP switch setting is read in the microcontroller only when the power is turned on. It isnecessary to turn the module on again after making any changes of SW2 settings.
Target sensor

SW2-1 setting

SW2-2 setting

TGS2600

OFFOFFTGS2602

OFFON

TGS2603

ONOFF2-4) Reset function: SW3
The reset switch is functional only in the normal mode. For more details, please refer to "3-3) Resetfunction".
2-5) Air quality level output and LED indication: D1 to D5
The blue LED blinks during the 2-minute warm-up period after the power is turned on, and the module
returns to normal mode once the warm-up is finished. In normal mode, the air quality level is output
using the 5 voltage levels shown in the table below, and the LED with the color corresponding to each
air quality level will come on.
* Air quality level output (VAQL) can be measured from the pin 3 of CN1.
* The assessment of air pollution levels is a subjective one and may vary from person to person.
LevelVAQL*LED color1Approx. 1V

D1: Blue

Clean

2Approx. 2V

D2: Green

Mildly polluted

3Approx. 3V

D3: Yellow-green

4Approx. 4V

D4: OrangeHeavily polluted

5Approx. 5V

D5: RedExtremely polluted

3

Degree of air pollution*

Moderately polluted

Fig 2. Image of LED lighting (when LED D4 is on.)2-6) Load resistance RL setting: JP1-JP3
The proper load resistance (RL) setting is required to measure the sensor output (VOUT) as follows.
The factory setting of the jumper pin JP is 10kΩ as a recommended value. Choose 51kΩ if VOUT
value is too small, or 2kΩ if it is too large for easy measurement of sensor output voltage VOUT.
* If RL is not selected, approx. 5V will be output from the pin 2 of CN1.
* When changing the jumper pin JP setting, turn the power off, change the pin setting, and thenturn the power back on.
Load resistanceSetting

2kΩ

JP110kΩJP251kΩJP3Sensor resistance (Rs) in kΩ is calculated from the sensor output VOUT using the following
formula:Rs = (VIN / VOUT -1) × RL2-7) Notes about sensor output (VOUT)
The sensor output voltage (VOUT) may vary even among the same sensor models due to individual
differences in sensor resistance. Also, VOUT can be varied by changing the load resistance (RL).

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3. How to use EM26AQS
EM26AQS operates as shown in the follow chart:

Power onWarm-up (for 2 minutes)

Normal mode

Reset function3-1) Warm-up period
For 2 minutes after turning on the power, the AQ Level 1 (clean) indication will be displayed
regardless of the degree of air pollution, and the blue LED will blink at 0.5 second interval.
After the warm-up period, the blue LED will stop blinking and go on. At the same time, theresistance value of the sensor (Rs) in the air pollution level at that time will be recorded in themicrocontroller as the initial reference value under the clean air.

3-2) Normal mode
The module will switch to normal mode once the warm-up is finished.
One of the LEDs with five different colors will illuminate, and a different air quality level output(VAQL) will be produced from the 3 pin of CN1, which corresponds to each level of air pollution.
During the normal mode, the reference value of the sensor resistance in the microcontroller issuccessively updated according to changes in the degree of air pollution, and the microcontroller
will continue to evaluate the degree of air pollution in 5 levels by comparing the current sensor
resistance value to the updated reference value.

3-3) Reset function
When the tactile switch (SW3) is pressed for 4 seconds or more during normal operation mode, thereference value will be forced to update to the sensor resistance value in the ambient air conditions
at that moment. The air quality level around the sensor at that time will be regarded as clean, andthe air quality level output (VAQL) will be reset (*) to 1V (i.e. Clean).

3-4) Sensor mounting
When mounting a gas sensor in its socket, ensure proper sensor orientation.
(Mounting the sensor incorrectly will result in inaccurate output.)54. Specifications
Model No.:

EM26AQS

Product Name:

Evaluation Module for Air Quality Sensors

Compatible gas sensors: TGS2600, TGS2602, TGS2603 (Extension Function: TGS2660 mode)
Input voltage:

5.0 ± 0.2VDC

Sensor output voltage:

Max. 5V (depending on input voltage)

Air quality level output:

Approx.1 to 5V

Operating temperature and humidity conditions:-10°C to 50°C, 0% to 95%RH (no condensation)

Dimensions:

Approx. 45 x 55 x 17 (mm) excluding gas sensor

Weight:Approx. 15g (excluding gas sensor)

5. Extension Function
As an extension function, the EM26AQS has a dedicated TGS2660 mode that facilitates theevaluation of the ventilation index sensor TGS2660.
The TGS2660 mode enables to provide 5 levels of the Ventilation Index Output (VIO) as an indicationof low-concentration indoor air pollution caused by room occupants using TGS2660 sensor.
5-1) Switch settings for TGS2660 Mode: SW2
Before turning on the power, set the Dip switch (SW2) as shown in the table below.
Target Sensor

SW2-1 Setting

SW2-2 Setting

TGS2660ONON

5-2) Ventilation Index Output and LED Indication: D1 to D5
As with the evaluation of TGS2600, 2602, and 2603 sensors, when used with TGS2660, theVentilation Index Output (VIO) is output using the five voltage levels and LED indication with different
colors corresponding to each ventilation index level.
The LED color corresponding to the Ventilation Index Output (VIO) and the state of air pollution are
shown in the table below. The Ventilation Index Output (VIO) can be measured from pin 3 of CN1.

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LevelVIO

Color of LED

Indoor Air Pollution Levels

Approximately
corresponding
CO2 concentration
ranges*1

approx.1V

D1：Blue

Clean indoor air level400～800ppm

2

approx.2V

D2：Green

Stale air

800～1500ppm

3

approx.3V

D3：Greenishyellow

4approx.4V

D4：Orange

5

approx.5V

D5：RedLevel associated withcomplaints ofdrowsiness and poor air.
Stagnant, stale, stuffy air,level associatedwith sleepiness
Very strong discomfort

1500～2500ppm
2500～5000ppm
5000ppm or over

* The corresponding CO2 concentration ranges are for reference purposes only. The information
contained in the table shall not be construed as a correlation between ventilation index levels andindoor CO2 concentrations.
5-3) Operation in TGS2660 mode
As with the evaluation of the other TGS260x series air quality sensors, the extension function includes
warm-up, normal mode, and reset functions. Please refer to "3. How to use EM26AQS " for details.
When the tactile switch (SW3) is pressed for 4 seconds or more during normal operation mode, thereference value will be forced to update to the sensor resistance value in the ambient air conditions
at that moment. The air quality level around the sensor at that time is regarded as clean, and theVentilation Index Output (VIO) will be reset (*) to 1V (i.e. clean air).

6. Dedicated PC Applications
By using the dedicated PC application for EM26AQS, air quality sensors can be easily evaluated,and measurement data can be saved in CSV format.
6-1) Acquisition of Dedicated Application Software Package
Please download the EM26AQS dedicated application software package from the following Figaro
website: “EM26AQS Product Details” Page
(Japanese site): https://www.figaro.co.jp/product/entry/em26aqs.html(English site): https://www.figaro.co.jp/en/product/entry/em26aqs.html(Chinese site): https://www.figaro.co.jp/cn/product/entry/em26aqs.html

Save the downloaded folder in the desired location on the PC (e.g., desktop). Open the folder
named "EM26AQSMeasure" saved on your PC and confirm that the executable files,
EM26AQSMeasure.exe and EM26AQSMeasure.exe.config, are present.
Icon of the dedicated application executable file:76-2) Installation Method for USB Drivers
Before starting the dedicated application, perform the following three installations:① USB DriverOpen the [USB Driver] folder in the dedicated application folder that was downloaded in theprevious step and double-click either of the following executable file icons to install the USB driver:For 32-bit Windows OS: "CP210xVCPInstaller_x86.exe"
For 64-bit Windows OS: "CP210xVCPInstaller_x64.exe"② .Net Framework 3.5

Download and install Microsoft .Net Framework 3.5 software from Microsoft website:(Japanese site): https://www.microsoft.com/ja-jp/download/details.aspx?id=22(English site): http://www.microsoft.com/en-us/download/details.aspx?id=22(Chinese site): https://www.microsoft.com/zh-CN/download/details.aspx?id=22③ MS Chart Controls

Download and install Microsoft Chart Controls from Microsoft website.
When downloading, make sure to check all boxes:(Japanese site): http://www.microsoft.com/ja-jp/download/details.aspx?id=14422(English site): http://www.microsoft.com/en-us/download/details.aspx?id=14422(Chinese site): http://www.microsoft.com/zn-CN/download/details.aspx?id=14422

6-3) Launching and Operation of the Dedicated Application① Attach the TGS26xx sensor to EM26AQS.

② Connect EM26AQS to the PC using a USB Type-C cable.
Power is supplied to EM26AQS through the USB cable.

③ Set SW1 (Power Input Switch) on EM26AQS to the CN3_ON position.

④ Double-click the icon of the dedicated application "EM26AQSMeasure.exe" installed on your PC
to display the startup screen as shown in Figure 3.

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Figure 3: Startup screen⑤ [COM No.] Setting COM Port Number

Select the COM port number that is automatically recognized by the PC application from the pulldown menu for "COM No." in the upper right corner of the screen.
⑥ [Save Interval] Setting Recording Interval

Select one of 2 seconds, 4 seconds, 10 seconds, 30 seconds, 60 seconds, 2 minutes, 5 minutes,
10 minutes, 30 minutes, or 60 minutes from the "Save Interval" pull-down menu on the right side of
the screen for the interval for recording measurement data in CSV format. (Note: The measurement
data graph displayed on the screen is updated at a fixed interval of one second.)⑦ [Save Folder] Setting Save Destination

The directory of the default save folder is displayed.
The destination for saving measurement data (CSV format file) can be changed by pressing the[Change] button when measurement data is not being conducted.
⑧ [Save File Name] Setting Save File Name

The measurement data is automatically saved with a file name following the format like
"AQS_20240516-1.csv", where the file name, which is input in [FileName], is followed by the date(20240516) and serial number (-1).
⑨ [Free Word] Inputting Free Words

You can input information or notes about the measurement into the [Free Word] field, which will berecorded in the header section of the CSV file.
⑩ Starting the Measurement

9Press the [Start] button to start the measurement. The graph will display the sensor output(a solid line) and the air pollution level output (a blue dashed line).
The measurement period is every 2 seconds, and the screen displays measurement datafrom approximately 10 minutes ago to the latest measurement data. (Figure 4)
Save the measurement data in CSV format on the PC according to the set recordinginterval.

Figure 4: Example of measurement data display⑪ Ending the Measurement

Press the [Stop] button to end the measurement. After ending, the measurement data is saved inCSV format.
6-4) Setting Various Parameters
Various parameters regarding sensor responses to indoor air pollution can be set by pressing [ToSetting] (Figure 5). The [To Setting] button is operable only when measurement is not in progress.
Press the [Read setting] button to read the parameter settings recorded in the MCU(Microcontroller) on the EM26AQS.
Press the [Write new setting] button to write the information of the settings displayed on thePC screen to the MCU of the EM26AQS that is connected to the PC.
Press the [Back] button to return to the measurement screen.
Details of parameter settings are as follows:
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① AQL threshold

G1 to G8: Setting values for increasing or decreasing AQL thresholds (Please refer to thefactory preset values shown on the left side of the screen for each sensor model.)T1_bench mark renewal: Time per segment for updating benchmark values
T2_delay timer: Time for the delay processing (*1) timer② Saturation func.threshold

G9 to G10: Threshold levels to control the saturation operation (*2)
T3_saturation timer: Time for saturation operation timer③ TGS2660 setting *Extension Function: Operable only when the TGS2660 mode is set.
T4_bench mark renewal: Time elapsed until starting benchmark value correction
Correction factor b: Correction value of ventilation index*For the factory settings of EM26AQS, G1 to G8 settings are preset suitable for evaluation
with TGS2600 and other settings are preset to the values that are calculated based on ourevaluation tests. Please modify settings according to the expected operating environment
and intended gas sensor application.
(*1) The Delay Processing is to gradually change AQL when the air quality changes rapidly from
polluted to clean state.
(*2) The saturation operation is a process of adjusting the AQL towards a cleaner direction if thesensor response is saturated at the same AQL while the air quality is judged to be polluted (AQL ≥2).
The saturation operation is turned on 2 seconds after AQL changes to AQL ≥ 2. Thesaturation operation timer starts when Rs/R02 ≤ G9. (where: R02 is the sensor resistancevalue 2 seconds before the current Rs).
The saturation timer is reset when Rs/R03 ≤ G10 (where: R03 is the sensor resistancevalue 3 minutes before the current Rs).

11Figure 5: Setting screen of various parameters6-5) Reset Function
The reset function can be also controlled on the dedicated PC application screen.
(Refer to 3-3) for details on the reset function.)
Press the [Reset] button to change the VAQL to 1V, assuming the air at that time is clean.
Figure 6 shows an example of executing the reset function when displaying VAQL = 4V on thegraph.

Figure 6: Example of executing the reset function

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7. Troubleshooting
The following are the possible causes and suggested actions to take when an abnormality occurs:
Fault conditions

None of the LEDs arelit.

The red LED isblinking.

Red LED lights up,then is blinking.
Green or yellow-green
LED hardly changes.

Possible causes

Suggested actions- Low power supply voltage- Power supply voltage is not input.

Please check the power supply.
Please set SW1 to the correct
configuration.

Failure of this module(Due to electrostatic damage toelectronic components, etc.)-Fault determination by themicrocontroller* To reset the fault condition, pleaseturn the power off and then turn itback on.

Sensor failure

Please replace the sensor.

Sensor is not installed, orincorrectly inserted.

Please install the sensor in thecorrect orientation.

VAQL does not change.
Selection error with SW2, or
VAQL changes
Incorrect parameter settings, orminimally orPolluted indoor air
significantly.
PC application doesnot operate.

Driver software is not installed.

Please set SW2 correctly.
Set parameters according to theenvironment.
Ensure sufficient ventilationindoors.
Properly install all the drivers in thePC as described in this document.
Then connect EM26AQS to PC topower on. Restart the PCapplication.

Microcontroller runaway due toexternal noise

Please turn the power off and thenturn it back on.

Other faults

Please contact the manufacturer.

Others* This module is designed for the evaluation of TGS26-series air quality sensors only and not forother purposes or applications.
For any product-related inquiries, please contact us using the information provided below.

Figaro Engineering Inc.
1-5-11 Senba-nishi, Minoh, Osaka 562-8505 JAPAN
Tel: (81) 72-728-2561
e-mail: figaro@figaro.co.jp

URL: www.figaro.co.jp

REV.07.24
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