y our specialist in innovating humidity & temperature sensors - 1 - digital relative humidity & temperature sensor RHT02 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 2. description: RHT02 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 RHT02 to be suited in all kinds of harsh application occasions. 3. technical specification: model RHT02 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 +-3%rh (max +-5%rh); temperature +-0.5celsius resolution or sensitivity humid ity 0.1%rh; temperature 0.1celsius repeatability humidity +-1%rh; temperature +-0.3celsius
y our specialist in innovating humidity & temperature sensors - 2 - humidity hysteresis +-0.5%rh long-term stability +-0.5%rh/year interchangeability fully interchangeable 4. dimensions of RHT02's pcb board(unit----mm) and wiring diagram: pin function 1 vdd----power supply , red wire 2 data--signal, yellow wire 3 gnd, black wire 4 null 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 RHT02. ( m axdetect 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.)
y our specialist in innovating humidity & temperature sensors - 3 - 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 RHT02 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, RHT02 change from standby- status to running-status . when mcu finishs sending the start signal, RHT02 will send response signal of 40-bit da ta that reflect the relative humidity and temperature to mcu. without start signal from mc u, RHT02 will not give response signal to mcu. one start signal for one response data from RHT02 that refl ect the relative humidity and temperat ure. RHT02 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.
y our specialist in innovating humidity & temperature sensors - 4 - ------------------ ------------------ ----------------- --------------- --------------- --------------- --------------- -------------- ----- 1) step 1: mcu send out start signal to RHT02 and RHT02 send response signal to mcu data-bus's free status is high voltage level. when communication between mcu and RHT02 begins, mcu will pull low data-bus and this process must beyond at le ast 1~10ms to ensure RHT02 could detect mcu's signal, then mcu will pulls up and wait 20-40us for RHT02's response. when RHT02 detect the start signal, RHT02 will pull lo w the bus 80us as response signal, then RHT02 pulls up 80us for preparation to se nd data. see below figure: ------------------ ------------------ ----------------- --------------- --------------- --------------- --------------- -------------- ----- 2). step 2: RHT02 send data to mcu when RHT02 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:
y our specialist in innovating humidity & temperature sensors - 5 - attention: if signal from RHT02 is always high-voltage-level , it means RHT02 is not wo rking 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 1.2 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 this specif ication. the RHT02 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 rht0 2's sensitive-elements and debase RHT02's sensitivity. (3) disposal when (1) & (2) happens step one: keep the RHT02 sensor at condition of temper ature 50~60celsius, humidity <10%rh for 2 hours; step two: after step one, keep the RHT02 sens or at condition of temper ature 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 mu ch better to keep the sensor at same temperature when
y our specialist in innovating humidity & temperature sensors - 6 - sensing. RHT02 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 RHT02's performance. (6) attentions to connection wires the connection wires' quality will effect communicati on'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 stop devices or any other occasion that failure of RHT02 may cause personal injury.
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