Your specialist in innovating humidity & temperature sensors

Digital relative humidity & temperature sensor RHT03
1. Feature & Application:*High precision*Capacitive type
*Full range temperature compensated*Relative humidity and temperature measurement*Calibrated digital signal*Outstanding long-term stability*Extra components not needed*Long transmission distance, up to 100 meters*Low power consumption*4 pins packaged and fully interchangeable

2. Description:
RHT03 output calibrated digital signal. It applys exclusive digital-signal-collecting-technique and humidity
sensing technology, assuring its reliability and stability. Its sensing elements is connected with 8-bit single-chipcomputer.
Every sensor of this model is temperature compensated and calibrated in accurate calibration chamber and thecalibration-coefficient is saved in type of programme in OTP memory, when the sensor is detecting, it will cite
coefficient from memory.
Small size & low consumption & long transmission distance(100m) enable RHT03 to be suited in all kinds ofharsh application occasions. Single-row packaged with four pins, making the connection very convenient.

3. Technical Specification:ModelPower supply
Output signal
Sensing element
Operating range
Accuracy

RHT03
3.3-6V DC
digital signal via MaxDetect 1-wire bus
Polymer humidity capacitor
humidity 0-100%RH;
temperature -40~80Celsius
humidity +-2%RH(Max +-5%RH); temperature +-0.5Celsius

Resolution or sensitivity
Repeatability

humidity 0.1%RH;
humidity +-1%RH;

temperature 0.1Celsius
temperature +-0.2Celsius-1-MaxDetect Technology Co., Ltd.
----------------------------------------Thomas Liu (Sales Manager)
Email: thomasliu198518@yahoo.com.cn , sales@humiditycn.com

http://www.humiditycn.com

Your specialist in innovating humidity & temperature sensors
Humidity hysteresis
Long-term Stability
Interchangeability+-0.3%RH+-0.5%RH/year
fully interchangeable

4. Dimensions: (unit----mm)

5. Electrical connection diagram:
6. Operating specifications:(1) Power and Pins
Power's voltage should be 3.3-6V DC. When power is supplied to sensor, don't send any instruction to the sensor
within one second to pass unstable status. One capacitor valued 100nF can be added between VDD and GND forwave filtering.
(2) Communication and signal
MaxDetect 1-wire bus is used for communication between MCU and RHT03. ( MaxDetect 1-wire bus isspecially designed by MaxDetect Technology Co., Ltd. , it's different from Maxim/Dallas 1-wire bus, so it'sincompatible with Dallas 1-wire bus.)
Illustration of MaxDetect 1-wire bus:
Data is comprised of integral and decimal part, the following is the formula for data.
DATA=8 bit integral RH data+8 bit decimal RH data+8 bit integral T data+8 bit decimal T data+8 bit check-sum-2-MaxDetect Technology Co., Ltd.
----------------------------------------Thomas Liu (Sales Manager)
Email: thomasliu198518@yahoo.com.cn , sales@humiditycn.com

http://www.humiditycn.com

Your specialist in innovating humidity & temperature sensors
If the data transmission is right, check-sum should be:
Check sum=8 bit integral RH data+8 bit decimal RH data+8 bit integral T data+8 bit decimal T data
Example: MCU has received 40 bits data from RHT03 as0000 0010 1000 1100 0000 0001 0101 1111 1110 1110
16 bits RH data
16 bits T data
check sumCheck sum=0000 0010+1000 1100+0000 0001+0101 1111=1110 1110
RH= (0000 0010 1000 1100)/10=65.2%RH
T=(0000 0001 0101 1111)/10=35.1
When highest bit of temperature is 1, it means the temperature is below 0 degree Celsius.
Example: 1000 0000 0110 0101, T= minus 10.1
16 bits T data
When MCU send start signal, RHT03 change from standby-status to running-status. When MCU finishs sending
the start signal, RHT03 will send response signal of 40-bit data that reflect the relative humidity and temperature
to MCU. Without start signal from MCU, RHT03 will not give response signal to MCU. One start signal for one
response data from RHT03 that reflect the relative humidity and temperature. RHT03 will change to standby
status when data collecting finished if it don't receive start signal from MCU again.
See below figure for overall communication process, the interval of whole process must beyond 2 seconds.

-3-MaxDetect Technology Co., Ltd.
----------------------------------------Thomas Liu (Sales Manager)
Email: thomasliu198518@yahoo.com.cn , sales@humiditycn.com

http://www.humiditycn.comYour specialist in innovating humidity & temperature sensors-----------------------------------------------------------------------------------------------------------------------------------1) Step 1: MCU send out start signal to RHT03 and RHT03 send response signal to MCU
Data-bus's free status is high voltage level. When communication between MCU and RHT03 begins, MCU
will pull low data-bus and this process must beyond at least 1~10ms to ensure RHT03 could detect MCU's signal,then MCU will pulls up and wait 20-40us for RHT03's response.
When RHT03 detect the start signal, RHT03 will pull low the bus 80us as response signal, then RHT03 pullsup 80us for preparation to send data. See below figure:-----------------------------------------------------------------------------------------------------------------------------------2). Step 2: RHT03 send data to MCU
When RHT03 is sending data to MCU, every bit's transmission begin with low-voltage-level that last 50us, thefollowing high-voltage-level signal's length decide the bit is "1" or "0". See below figures:-4-MaxDetect Technology Co., Ltd.
----------------------------------------Thomas Liu (Sales Manager)
Email: thomasliu198518@yahoo.com.cn , sales@humiditycn.com

http://www.humiditycn.com

Your specialist in innovating humidity & temperature sensors

Attention:
If signal from RHT03 is always high-voltage-level, it means RHT03 is not working properly, please checkthe electrical connection status.

7. Electrical Characteristics:
Items
Power supply
Current supply
Collecting
periodCondition
DCMeasuring
Stand-bySecondMin
3.3
140

Typical
5
Null2

Max
6
1.5
50

Unit
VmAuA
Second8. Attentions of application:(1) Operating and storage conditions
We don't recommend the applying RH-range beyond the range stated in this specification. The RHT03 sensor
can recover after working in abnormal operating condition to calibrated status, but will accelerate sensors' aging.
(2) Attentions to chemical materials
Vapor from chemical materials may interfere RHT03's sensitive-elements and debase RHT03's sensitivity.
(3) Disposal when (1) & (2) happens
Step one: Keep the RHT03 sensor at condition of Temperature 50~60Celsius, humidity <10%RH for 2 hours;
Step two: After step one, keep the RHT03 sensor at condition of Temperature 20~30Celsius, humidity>70%RH for 5 hours.
-5-MaxDetect Technology Co., Ltd.
----------------------------------------Thomas Liu (Sales Manager)
Email: thomasliu198518@yahoo.com.cn , sales@humiditycn.com

http://www.humiditycn.com

Your specialist in innovating humidity & temperature sensors(4) Attention to temperature's affection
Relative humidity strongly depend on temperature, that is why we use temperature compensation technology
to ensure accurate measurement of RH. But it's still be much better to keep the sensor at same temperature whensensing.
RHT03 should be mounted at the place as far as possible from parts that may cause change to temperature.
(5) Attentions to lightLong time exposure to strong light and ultraviolet may debase RHT03's performance.
(6) Attentions to connection wires
The connection wires' quality will effect communication's quality and distance, high quality shielding-wire isrecommended.
(7) Other attentions* Welding temperature should be bellow 260Celsius.
* Avoid using the sensor under dew condition.
* Don't use this product in safety or emergency stop devices or any other occasion that failure of RHT03 may
cause personal injury.

-6-

MaxDetect Technology Co., Ltd.
----------------------------------------Thomas Liu (Sales Manager)
Email: thomasliu198518@yahoo.com.cn , sales@humiditycn.com

http://www.humiditycn.com