MEMS Acetone Sensor

Introduction

Acetone sensor is MEMS-technology based gas sensor with semiconductor nanomaterial as sensing material, which can detect acetone of different concentrations in exhaled breath.

Characteristic

The sensor has the characteristics of small size, low power consumption, high sensitivity, low cost, fast response, high stability, long lifetime, etc.

Main application

S1015 sensor can detect acetone of different concentrations in human exhaled breath, which can provide respiratory related medical diagnosis, health tracking and big data services.

Technical Parameters

Pin Assignment & Reference Circuit

Characteristic figures

Figure4: The sensitivity curve of sensors

Figure5: The response curve of the sensor

Figure6: The sensitivity of the sensor versus temperature

Figure7: Stability test of sensors

M1015 Acetone sensor module

MMD1015 acetone gas sensor module is a module developed using MEMS micro gas sensor, which can be used to detect the acetone content in breath.

High sensitivity, high resolution, low power consumption, and long service life  Provide  UART,  analog  voltage  signal,  PWM  waveform  and  other  output methods with high stability and excellent linear output.

Application: 

Breath detector.

Technical Parameters

Module Size:

UART communication setting parameters

1.  General settings: Use UART communication interface, the settings are as follows, Table 1:

Communication is active upload method, the module sends data in every 3 seconds. The data format show as following:

2.   Communication command: Communication is divided into active upload type, and data is sent once every 3S.The format of data transmission is as follows,

The data length reported by the serial port of the module is fixed at 24 bytes, and the current valid bits are:

Frame header (0xAA) + temperature (4 bytes) + humidity (4 bytes) + voltage 1 + voltage 2 (reserved) (voltage is 4 bytes) + gas type (1 byte) + gas concentration (4 bytes) + alarm / level (1 byte) + 24th byte is fixed as cumulative check code

When 4 bytes of data such as temperature, voltage, concentration,   etc. are parsed into hexadecimal in hexadecimal, the high bit of the original data is in the back, and the low bit is in the front. After rearrangement, it is converted into a decimal integer, and then     divided by 1000 to get the decimal float Points.

Examples:

AA A8 61 00 00 50 C3 00 00 DC 02 00 00 00 00 00 00 0B 20 4E 00 00 01 1D

Frame header AA

Address 00

Temperature A8 61 00 00-> 61 A8 (hexadecimal)-> 25000 (decimal)-> 25.000 (divide by 1000)

Humidity 50 C3 00 00-> C3 50-> 50000-> 50.000

Voltage 1 DC 02 00 00-> 02 DC-> 732-> 0.732

Voltage 2 (reserved) 00 00 00 00-> 0

Gas type 0B-> 11

Gas concentration 20 4E 00 00-> 4E 20-> 20000-> 20.000

Alarm level 01

Inspection code (cumulative) 1E

The parsing procedure of accumulated check code (including frame header) is as follows:

uint8_t CheckSum (uint8_t * p, uint8_t len)

{

uint8_ti;

uint32_t sum = 0;

for (i = 0; i <len; i ++)

{

sum + = p [i];

}

sum = sum & (0xFF);

return sum;

}

Serial commands:

The module can send commands through the serial port to achieve some functions, as follows:

(1) AA 00 FA

Switch the module to question and answer mode or active upload, the  module initializes the default active upload mode, and you can switch between the two modes through this command.

2) AA 00 F9

In Q & A mode, the module data is fetched through this command, and the data return format is the same as the active upload format.

(3) AA 00 FE BB Algorithm reset

(4) AA 00 FB

Toggle decimal floating point output

The decimal output format is as follows:

Table 2:

Note: The data is sent as a string, with spaces between the data.

Notes:

1.   Conditions that must be avoided

1.1 Exposure to volatile silicon compound vapors

The module should be protected from silicon adhesive, hair gel, silicone rubber, putty or other places where volatile silicon compounds are present. Otherwise it will cause the sensitivity of the module is reduced and it will not even respond.

1.2 Highly corrosive environment

The module is exposed to high concentrations of corrosive gases (such as H2S, SOX, Cl2, HCl, etc.), which will cause the sensors in the module to heat the material And sensor lead corrosion or damage, and will  cause  irreversible deterioration of the performance of sensitive materials, which will affect the performance and accuracy of the module.

1.3 Contact with water

If the sensor in the module is splashed or immersed in water, it will cause the sensor's sensitivity characteristics to decrease and affect the measurement accuracy of the module.

1.4 Icing

The icing on the surface of the sensor's sensitive material of the module will cause the sensitive layer to crack and lose its sensitive characteristics.

2 Conditions to avoid as much as possible

2.1 Condensate

Under indoor use conditions, slight condensation of water will have a slight impact on the sensor performance in the module. But if water condenses on the surface of the sensitive layer And hold it for a period of time, the sensor characteristics in the module will decrease, and the measurement error of the module will increase.

2.2 in high concentration gas

Regardless  of whether the  module  is  powered  on,  long-term  placement  in  high- concentration gas will affect the sensor characteristics  in the  module.  If spraying directly with lighter gas to the sensor in the module, it will cause great damage to the sensor in the module, and will cause the sensitivity of the module to decrease.

2.3 Long-term storage

When the module is stored for a long time without power, the resistance of its sensor will produce a reversible drift, which is related to the storage environment. mold

The group should be stored in a sealed bag containing no volatile silicon compounds. Modules that have been stored for a long time require more time to power up before use.  To stable. The storage time and the corresponding aging time are recommended as follows:

2.4 Long-term exposure to extreme environments

Regardless of whether the module is energized or not, if it is exposed to extreme conditions for a long time, such as extreme conditions such as high humidity, high temperature or high pollution, the module performance will be seriously affected.