AM (wired DHT22) temperature-humidity sensor . DHT11 datasheet (https ://)(in chinese, so see the DHT22 datasheet too!). AM digital temperature and humidity module is a digital output signal containing a calibrated temperature and humidity combined sensor. It uses a. AM Datasheet PDF Download – Digital temperature and humidity sensor, AM data sheet.

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Similarly the Sensirion SHT21 not included here also has a near identical specification and interface. Below that I had not problems and above they were intermittent but fine most of the time.

The DHT11 is clearly a different class of sensor with substantially lower dayasheet and has been dropped from further investigation.

The difference is so stark that it leads me to believe the sensing element is in some way fundamentally different from the other devices. All the other sensors were multiplexed onto the I2C bus. My current supposition is zm2302 it uses a resistive film rather than a capactive film.

The difference is small 0. All agree within about 0. If you are trying to interface DHT22 with Arduino Uno then there are ready made libraries for datashheet which will give you a quick start. I do not distinguish between the case of the sensor having a very slow response many hours but eventually asymptotically approaching the ‘true’ value and the case of a sensor that is permanently biased by its history and would never reach the same ‘true’ value when approaching from above or below.

For the other sensors, where the slope of my data matches the slope of the reference datashest e.

(PDF) AM2302 Datasheet download

The devices on the lower row are all shown mounted on third party break-out boards that make it easy to interface the surface mount device to 2. For details of how the experiment works, datsheet refer to the previous wm2302. This is a good thing because it allows some head room for small errors in the calibration. It was zm2302 by reading the internal serial numbers I was able to ascertain that.

Blue data are from Greenspancyan data from O’Briengreen from Rockland and yellow, Wexler If you are trying to interface it with some other MCU then the datasheet given below will come in handy. The DHT22 Sensor is factory calibrated and outputs serial data and hence it is highly easy to set it up. In the right hand panel the lag has been arbitrarily removed and the values normalised in order to compare the intrinsic response speed of the sensor elements.


Throughout the following plots you will notice the data for sensor G are a little more darasheet than the others. Blue shows low readings and red are high.

Most of the others seem comparable to each other except the Si which is the one major outlier. A small adjustment to the internal calibration parameters could possibly bring this device to very nearly match the BME Either way wm2302 performance of the sensor is same. The AM and SHT71 devices have proprietary one-wire serial interfaces and were addressed independently, each using a separate GPIO pin as in the previous experiments.

It is a feature of all the AM23xx devices that they return a cached value from memory meaning they will always appear to respond to datashset change one reading 6 seconds later than the others.

It is also the only model for which every device I own performs within specification. Notes on particular sensors: As far as I have been able to acertain, all the other devices are polymer capacitance hygrometers.

The data scatter is small and the calibration error is linear in both the humidity and temperature directions. In normal use they are interchangeable both in terms of specification and communications protocols and even have the same I2C address so are drop-in replacements for each other. datasheeet

Surfaces showing deviation of each sensor from the true relative humidity as a function of temperature and humidity. The plots and numerical analysis were generated in FlotOctaveD3 and Plotly javascript. Finally, if a sensor is to be used to measure humidity under a range of varying temperatures a full bivariate calibration is required.

Cyan data from O’Brien and yellow from Wexler It worked again immediately once the humidity dropped. A separate document covers absolute temperature calibration of the BME and also demonstrates that though the results here are strictly only relative, within a couple of tenths of a degree they are also good representations of the absolute accuracy.


It has been moved out into a separate document since rendering nine surfaces simultaneously proved an excessive load for some web browsers. It has a very rapid response, good if you need it, but will likely need filtering and smoothing if you are more interested in meteorological humidity.

The devices now included are: I am experimenting the WebGL 3D surface renders on this page and have had problems with very slow page loads in some browsers. For all other data on this page the filter was enabled.

AM2302 Datasheet PDF

The hysteresis curve traces a tight envelope and was highly repeatable on the two cycles performed. Plots showing deviation of each device’s own temperature from the average of all nine, plotted as a function of datsheet.

Pin Identification and Configuration No: The sampling rate is controlled by setting the 0xF5 memory register and the various speed options are defined in the datasheet. Absolute accuracy seems comparable to the other sensors apart from the BME Currently I am attributing it to bad luck in my zm2302 a couple of faulty devices rather than a systematic fault with this model.

I made no attempt here to establish an absolute temperature calibration and simply compare each sensor to the ensemble average of all nine sensors. If the device caps output at 0— it makes it difficult to apply your own re-calibration near the limits. To show those differences in more detail I present plots for a single chemical as the temperature is systematically varied.

DHT22 Sensor Pinout, Specs, Equivalents, Circuit & Datasheet

Repeatability at a fixed datashert is very good. I have seen the same third party generic break-out boards being sold with any one of these devices attached. Hystersis was almost undetectable. Here I use the term hysteresis only to refer to the lagging of the sensor behind the current conditions.