ZMOD4410 Datasheet

© 2021 Renesas Electronics Corporation

13

December 17, 2021

8.2 Odor (Relative Measurement)

Operation Mode 4 can be used to control an external device, such as a fan or ventilation system, based on changes in Air Quality.

Renesas provides firmware and algorithms, which allow the ZMOD4410 to learn its environment. The gas sensor module will only respond to

changes in the ambient conditions by detecting changes in the relative ambient TVOC concentration. The sensor module outputs are raw

resistance measurements and an algorithmic calculation of the air quality change, which indicates a total air quality change over time. It is

defined as the following:



Air Quality Change < 1: Improvement of air quality, overall gas concentration is falling



Air Quality Change = 1: No change in air quality



Air Quality Change > 1: Deterioration of air quality, overall gas concentration is rising

In addition, a control state is given, which shows the status of a user-defined threshold. When a user-defined threshold is exceeded, an I/O

control signal (trigger) based on the algorithm output may control an external device. Recommendation: Activate the external device for at least

a few minutes (stop delay time) to ensure air quality improvement and avoid an on-off activation at the threshold limit (hysteresis). Depending

on the application, you may adjust the threshold trigger and stop delay time.

Table 9.

Control Parameters for Odor Operation

Parameter

Conditions

Typical Value

Unit

Learning Time Environment

Typical value valid for sample rate of 2 seconds

60

min

Sensor Module Response Time

Sample rate dependent, typically 1 to 3 samples

5

s

Threshold Trigger

Change of raw sensor module signal; recommended difference: 30%

1.3

–

Stop Delay

Stop delay for external device; defines minimum activation time

2

min

When using the ZMOD4410 Evaluation Kit, the AD5 pin (GPIO) on connector K3 on the ZMOD4410 HiCom Communication Board is the trigger

control signal output that is set to HIGH/LOW for Operation Mode 4. For more information, see the ZMOD4410 Evaluation Kit User Manual.

8.3 Sulfur-based Odor Discrimination

Operation Mode 5 can be used to identify if a sulfur-smelling odor is present. When the target gas families have been defined through analysis,

a sweeping method allows for chemical discrimination. A machine learning embedded artificial intelligence (AI) algorithm makes use of a MOx

surface temperature array to get to a selectivity approach.

This operation mode classifies the odors in “sulfur” (sulfur-based) and “acceptable” (organic based) and shows an intensity level of the smell.

Acceptable odors are, for example, coming from air refreshers, soaps, perfumes etc., while bad smelling sulfur-based odors come from personal

odors in bathrooms. Because impression of smell is very unique, there might be overlaps with how people perceive odors. To bring this in an

A range of organic sulfur compounds are considered from the low ppb to the ppm range. The typical sample rate is 3 seconds, but the algorithm

may need a few samples for the correct classification.

This sulfur-based odor discrimination firmware was developed based on known commercially available products that represent both bad and

acceptable odors. Other places with unknown chemical signatures can lead to incorrect algorithm results. Training the sensor module and

developing the discrimination for other gases and applications may be considered for future releases.

8.4 Conditioning and Stability

The ZMOD4410 will respond to TVOC immediately upon start-up; however, a conditioning period of 48 hours followed by a sensor module

restart in an ambient environment is recommended to improve stability and obtain maximum performance. This restart can be done either by a

full sensor restart or by reinitializing the sensor algorithms. After a full sensor restart (power down or RES_N pin) the sensor must be

reconfigured.