y our specialist in innovating humidity & temperature sensors - 1 - digital relative humidity & temperature sensor RHT01 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: RHT01 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 RHT01 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 RHT01 power supply 3.3-6v dc output signal digital signa l via maxdetect 1-wire bus sensing element polymer humidity resistor operating range humidity 20-90%rh; temperature 0~50celsius accuracy humidity +-5%rh ; temperature +-2celsius resolution or sensitivity humidity 1%rh; temperature 1celsius repeatability humidity +-2%rh; temperature +-1celsius humidity hysteresis +-1%rh long-term stability +-1%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 RHT01. ( 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 RHT01 as 0010 0001 0000 0000 0001 1010 0000 0000 0011 1011 16 bits rh data 16 bits t data check sum here we convert 16 bits rh da ta from binary system to decimal system, 0010 0001 0000 0000 33 binary system decimal system rh=33.0%rh here we convert 16 bits t da ta from binary system to decimal system, 0001 1010 0000 0000 26 binary system decimal system t=26.0 when highest bit of temperature is 1, it mean s the temperature is below 0 degree celsius. example: 1 000 1010 0000 0000 , t= minus 10 16 bits t data sum=0010 0001+0000 0000+0001 1010+0000 0000=0011 1011 check-sum =the last 8 bits of sum=0011 1011 when mcu send start signal, RHT01 change from standby-status to running-status. when mcu finishs sending the start signal, RHT01 will send response signal of 40-bit data that reflect the relative humidity and temperature to mcu.
y our specialist in innovating humidity & temperature sensors - 3 - without start signal from mcu, RHT01 w ill not give response signal to mcu. one start signal for one response data from RHT01 that reflect the relative humi dity and temperature. RHT01 will change to standby status when data collecting fi nished 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 RHT01 and RHT01 send response signal to mcu data-bus's free status is high voltage level. when communication be tween mcu and RHT01 begins, mcu will pull low data-bus and this process must beyond at least 1~ 10ms to ensure RHT01 could detect mcu's signal, then mcu will pulls up and wait 20-40us for RHT01's response. when RHT01 detect the start signal, RHT01 will pull low the bus 80us as response signal, then RHT01 pulls up 80us for preparation to send data. see below figure:
y our specialist in innovating humidity & temperature sensors - 4 - ------------------ ------------------ ----------------- --------------- --------------- --------------- --------------- -------------- ----- 2). step 2: RHT01 send data to mcu when RHT01 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 RHT01 is always high-voltage-level, it means RHT01 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
y our specialist in innovating humidity & temperature sensors - 5 - 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 RHT01 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 1's sensitive-elements and debase RHT01's sensitivity. (3) disposal when (1) & (2) happens step one: keep the RHT01 sensor at condition of temper ature 50~60celsius, humidity <10%rh for 2 hours; step two: after step one, keep the RHT01 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. RHT01 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 RHT01'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 RHT01 may cause personal injury.
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