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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AM Datasheet PDF –
The one-wire serial of the AM is retained making this a simple drop-in replacement. Cyan data from O’Brien and yellow from Wexler datwsheet As expected, all sensors do show the tendency to read systematically high when the humidity is decreasing and read low when humidity is rising. Hystersis was almost undetectable. They have remained fairly consistent over the six months between the two experiements.
The sensor is also factory calibrated and hence easy to interface with xm2302 microcontrollers. The data scatter is small and the calibration error is linear in both the humidity and temperature directions.
AM2302 Datasheet PDF
The left panel shows the actual results you would get when using the device and the right panel more directly compares the intrinsic physical response of the sensor elements. Each humidity level was held for twelve hours and the measured value logged every half hour. For example, with the highly responsive HTU21D, I often see spikes and wobbles in the readings as I move around the room, stiring the air.
Currently I am attributing it to am22302 luck in my getting a couple of faulty devices rather than a systematic fault with this model. When running at the default full speed my device returned temperatures datasjeet. Time response of the devices when exposed to a sudden upwards change in humidity. Over two years, three of the original six devices have failed.
Here I use the term hysteresis only to refer to the lagging of the sensor behind the current conditions. Within the data obtained here, the BME is the undisputed winner. The intent had been to include an identical pair of sensors with and without the cover, however when my devices arrived I found the retailer had sent me HTU21s without the cover and Sis with the cover.
These two particular BMEs consistently read a higher temperature than all the other devices, though datasehet I have tested subsequently in my investigation of absolute thermometer accuracy have not all followed that pattern. The devices are powered continuously, but the I2C IO lines are briefly connected to each device in turn.
For all other datasehet on this page the filter was enabled. In contrast, the AM device G shows little error as a function of humidity Figure 12 but has the largest error as a function of temperature Figure 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 a a2m302 one reading 6 seconds later than the others.
To show those differences in more detail I present plots for a single chemical as the temperature is systematically varied. In summary, they appeared similar to the DHT22 most of the time, but I had so many different intermittent problems I do not intend to use these devices in future experiments.
Each of these three sensors showed advantages in one paramter or another, but given that I am only testing one example of each I cannot say if those are features of the device type or just my particular specimen.
I do not distinguish datasheeet 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 datashwet would never reach the same ‘true’ value when approaching from above or below.
Blue data are from Greenspancyan data from O’Briengreen from Rockland and yellow, Wexler The other six are new and this is their first test.
(PDF) AM2302 Datasheet download
That is not to say they will all perform identically. First, unlike all the other devices tested it includes a barometer. At one sample per second values agreed with the polled operating mode where the device was put to sleep between readings.
In its default configuration, rather than taking a reading on demand, the device continuously reads values as fast as it can, returning the latest available value on request. Readings were taken once every six seconds. Similarly the Sensirion SHT21 not included here also has a near identical specification and interface.
In any case, they fulfill the manufacturer’s specified 1. Plotted for comparison are values taken from the published literature. I never got to the bottom of whether this was something wrong in my set-up or an intrinsic sensor fault. The BME shows outstanding calibration throughout.