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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DHT22 Sensor Pinout, Specs, Equivalents, Circuit & Datasheet
The shaded grey region is the specified tolerance from the manufactuers’ datasheets. Plots showing deviation of each device’s own temperature from the average of all nine, plotted as a function of humidity. The test is potentially unfair though given that they were brand new and are being compared against two-year old DHT22s and SHT Where the slopes of the measurements and reference data differ e.
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 change one reading 6 seconds later than the others. The dark grey lines are the new hystersis test and create envelope inside which all the readings will fall. Serial data Temperature Range: For the other sensors, where the slope of my data matches the slope of the reference data e. I discuss these together though they are distinct devices from two different manufacturers.
All the other sensors were multiplexed onto the I2C bus. Currently I am attributing it to bad luck in my getting a couple of faulty devices rather than a systematic fault with this model. Since the AM23xx devices return a previously cached value, they show the step change with a lag of one data point. Again I wonder if this suggests fundamentally different sensor technology from the other devices.
Though I designed and integrated the entire experiment, I must acknowledge the many open source projects, both software and hardware, that I used.
The difference is small 0. This is the device with a protective cover over the sensor and though it may seem reasonable that the membrane would slow the response, tests performed elsewhere showed it has almost no effect, slowing the devices readings by only about 1sec.
AM Datasheet PDF –
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. I have nothing much specific to say about this, but I mean that in a good way. At least the values are obviously wrong and an extra function was added to the microcontroller code to simply reject the dqtasheet data.
This device is a bit different. Front Page Kimberly Robert Hygrometers.
A sensor with hysteresis will tend to give low readings if it has recently been exposed to dry air and tend to read high when it has recently been exposed to datawheet air. The Bosch website, datasheet and press releases contain no information that I have been able to find about what am3202 inside the BME My current hypothesis is that the sensor element is contaminated and I have some experiments ongoing March to investigate that.
The large scatter of the blue points however show that the calibration degrades rapidly with varying temperature. Easily the best performers though are the BME which are both accurate and consistent over the range tested.
Two complete cycles of the loop from wet to dry and back to wet were performed. As far as I have been able to acertain, am2320 the other devices are polymer capacitance hygrometers.
I am not sure.
(PDF) AM2302 Datasheet download
Deviations from the known reference value as humidity is systematically cycled from high to low and back to high. Though an interesting addition and I will write about it elsewhere, for the present report I present only the temperature and humidity data. Though not discussed in detail on this page, the effect of using the protective cover on the response speed has been investigated elsewhere.
If the device caps output at 0— it makes it difficult to apply your own re-calibration near those limits. Here I use the term hysteresis only to refer to the lagging of the sensor behind the current conditions. At one sample per second values agreed with the polled operating mode where the device was put to sleep between readings.
Where blue dots scatter outside the shaded region it indicates a drift in the calibration as a function of temperature. The DHT11 is clearly a different class of sensor with substantially lower specification and has been dropped from further investigation.
Blue data are from Greenspanqm2302 data from O’Briengreen datazheet Rockland and yellow, Wexler Currently I am operating on a belief that it is a resistive sensor, measuring the electrical resistence through a porous film rather than the capacitance across a film like the other devices.