product name： | Digital temperature and humidity module |
Model： | MHTCI |
version： | V1.0 |
Creator： | He Genwen |
reviewed by： | Yuan Chao |
1、DESCRIPTION：
This product is a temperature and humidity integrated sensor with calibrated digital signal output. It uses imported sensing components and digital signal output, which has the characteristics of long-term stability, high reliability, high accuracy, low power consumption, and is not affected by power noise and voltage fluctuations. It is widely used in HVAC automatic control, temperature controllers/thermostats, computer room monitoring, white goods, indoor weather stations, and automotive climate control, Medical and other fields;
2、performance index：
■ | Supply Voltage | DC 5V |
■ | measurement accuracy | temperature：±0.4℃ humidity：± 3%RH |
■ | measuring range | humidity 0%— 100%RH temperature --40℃ －85℃ |
■ | power consumption | work： <1mA Standby： 150uA(3V) |
■ | data interface | standard I2C |
■ | resolution ratio | temperature 0.1℃ humidity :0.1%RH |
3、 I2C Interface Definition
3.1 Sensor Pin Allocation Table 1: Pin Allocation
Pin | name | describe |
1 | GND | grounds |
2 | VCC | Power supply DC5V |
3 | SCL | clock signal |
4 | SDA | Serial data, bidirectional port |
3.2 Power pin (VCC GND)
The power supply voltage of this product is DC5V
3.3 Serial Clock (SCL)
Figure 1: Pin allocation
SCL is used for communication synchronization between microprocessors and sensors。
3.4 Serial Data (SDA)
The SDA pin is a three state structure used for reading and writing sensor data. When sending commands to sensors, SDA is effective on the rising edge of SCL and must remain stable at high SCL levels. SDA changes after the falling edge of SCL. When reading data from sensors, SDA becomes effective after SCL decreases and maintains until the falling edge of the next SCL
Figure 2 Host Write Command 
Sensor output data
Table 2 I/O Signal Characteristics Table
4、Sensor Communication Description 4.1 I2C Signal Description
1) 7-bit addressing address
Start timing S
Stop timing P
I2C bus interface timing diagram
Each transmission sequence starts with the Start state. When SCL is at high level, SDA converts from high level to low level
Each transmission sequence ends with a Stop state. When SCL is at a high level, SDA converts from a low level to a high level
4.2 Timing Description
The parameters used are as follows
I2C Command Address Byte
I2C Command Table
Ask the register to describe the following program
Humidity calculation
temperature calculation
5、Basic Connection Diagram
Due to the addition of a 10K pull-up resistor inside the sensor, it can be directly connected and used when the communication distance is not very far. If the communication distance is too far, an external pull-up resistor must be added to ensure normal and reliable communication.
6、Specifications and dimensions
7、Application Information
7.1 Working and storage conditions
The relative humidity of the environment is greatly affected by temperature. When installing, the sensor should be kept as far away as possible from electronic components with high working temperature rise, while maintaining good ventilation.
7.2 Exposure to chemicals
This product is similar to a capacitive humidity sensor and is more sensitive to chemical vapors. The diffusion of chemicals in the sensing layer can lead to inaccurate measurement data and decreased reaction sensitivity.
