y our specialist in innovating humidity & temperature sensors - 1 - 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-signa l-collecting-technique and humidity sensing technology, assuring its reliability and stability. its sensing elements is connected with 8-bit single-chip computer. every sensor of this model is temperature compensate d and calibrated in accurate calibration chamber and the calibration-coefficient is save d in type of programme in otp memory, wh en the sensor is de tecting, it will cite coefficient from memory. small size & low consumption & long tran smission distance(100m) enable RHT03 to be suited in all kinds of harsh application occasions. single-row packaged with four pins, making the connection very convenient. 3. technical specification: model RHT03 power supply 3.3-6v dc output signal digital signa l via maxdetect 1-wire bus sensing element polymer humidity capacitor operating range humidity 0-100%rh; temperature -40~80celsius accuracy humidity +-2%rh (max +-5%rh); temperature +-0.5celsius resolution or sensitivity humid ity 0.1%rh; temperature 0.1celsius repeatability humidity +-1%rh; temperature +-0.2celsius humidity hysteresis +-0.3%rh long-term stability +-0.5%rh/year interchangeability fully interchangeable 4. dimensions: (unit----mm)
y our specialist in innovating humidity & temperature sensors - 2 - 5. electrical connection diagram: 6. operating specifications: (1) power and pins power's voltage should be 3.3-6v dc. when power is supp lied to sensor, don't send any instruction to the sensor within one second to pass unstable status. one capac itor valued 100nf can be added between vdd and gnd for wave filtering. (2) communication and signal maxdetect 1-wire bus is used for communication between mcu and RHT03. ( maxdetect 1- wire bus is specially designed by maxdetect technology co., ltd. , it's different from maxim/dallas 1-wire bus, so it's incompatible with dallas 1-wire bus.) illustration of maxdetect 1-wire bus: data=16 bits rh data+16 bits temperature data+8 bits check-sum example: mcu has received 40 bits data from RHT03 as 0000 0010 1000 1100 0000 0001 0101 1111 1110 1110 16 bits rh data 16 bits t data check sum here we convert 16 bits rh da ta from binary system to decimal system, 0000 0010 1000 1100 652 binary system decimal system rh=652/10=65.2%rh here we convert 16 bits t da ta from binary system to decimal system, 0000 0001 0101 1111 351 binary system decimal system t=351/10=35.1 when highest bit of temperature is 1, it mean s the temperature is below 0 degree celsius. example: 1 000 0000 0110 0101 , t= minus 10.1 16 bits t data sum=0000 0010+1000 1100+0000 0001+0101 1111=1110 1110 check-sum =the last 8 bits of sum=1110 1110 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- b it data that reflect the relative humidity and temperature
y our specialist in innovating humidity & temperature sensors - 3 - 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. ------------------ ------------------ ----------------- --------------- --------------- --------------- --------------- -------------- ----- 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 be tween 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 pulls up 80us for preparation to send data. see below figure: ------------------ ------------------ ----------------- --------------- --------------- --------------- --------------- -------------- -----
y our specialist in innovating humidity & temperature sensors - 4 - 2). step 2: RHT03 send data to mcu when RHT03 is sending data to mcu, every bit's tran smission begin with low-voltage -level that last 50us, the following high-voltage-level signal's length decide the bit is "1" or "0". see below figures: attention: if signal from RHT03 is always high-voltage-level, it means RHT03 is not working properly, please check the electrical connection status. 7. electrical characteristics: items condition min typical max unit power supply dc 3.3 5 6 v measuring 1 1.5 ma current supply stand-by 40 null 50 ua collecting period second 2 second 8. attentions of application: (1) operating and storage conditions we don't recommend the applying rh-range beyond the ra nge stated in th is specification. the RHT03 sensor
y our specialist in innovating humidity & temperature sensors - 5 - 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 rht0 3's sensitive-elements and debase RHT03's sensitivity. (3) disposal when (1) & (2) happens step one: keep the RHT03 sensor at condition of temper ature 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. (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 when sensing. RHT03 should be mounted at the pl ace as far as possible from parts that may cause change to temperature. (5) attentions to light long time exposure to strong light and ul traviolet 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 is recommended. (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 st op devices or any other occasi on that failure of RHT03 may cause personal injury.
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