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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This device is a bit different. It seems well made and has not dataaheet shown any problems in well over two years of continuous operation. I never got to the bottom of whether this was something wrong in my set-up or an intrinsic sensor fault.

The others all continue uneffected but values were only logged from this sensor when they were sensible.

(PDF) AM2302 Datasheet download

The Bosch website, datasheet and press releases contain no information that I have been able to find about what is datasjeet the BME It is a nice compact and apparently robust unit, especially with the optional cover screen.

Time response of the devices when exposed to a sudden upwards change in humidity. Readings were taken once every six seconds. My Si is arguably the poorest of the three with larger thermal shifts and hysteresis, 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.

Time response of the devices when exposed to a sudden downwards change in humidity. The hysteresis curve traces a tight envelope and was highly repeatable on the two cycles performed.

Blue data are from Greenspancyan data from O’Briengreen from Rockland and yellow, Wexler The same device as was used in previous tests. So if you are looking to measure in this range then this sensor might be the right choice for you.

Since the AM23xx devices return a previously cached value, they show the step change with a lag of one data point.

I never found ratasheet cause or have any suggestion for why they should fail to produce output in such a narrow range of humidity. Almost vaguely related and possibly of interest is monitoring radon in the house.


DHT22 Sensor Pinout, Specs, Equivalents, Circuit & Datasheet

The hysteresis envelope was nice and tight. 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. Below that I had not problems and above they were intermittent but fine most of the time.

Where the slopes of the measurements and reference data differ e. Plots showing deviation of each device’s dataaheet temperature from the average of all nine, plotted as a function of humidity.

Be careful with variable types in your software. TL — Programmable Reference Voltage. The left panel shows eatasheet actual results you would get when using the device and the right panel more directly compares the intrinsic physical response of the sensor elements. 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.

AM Datasheet PDF –

Plotted for comparison are values taken from the published literature. As previously noted, this is my cherry-picked, best AM from a sample of six. 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. 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.

Data obtained at other temperatures are shown in blue. For this reason I plot both the raw data where the AM23xx devices can all be seen to lag by one reading and also a version where that offset has been artifically removed. 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.

Though equivalent for most normal use, the precise specification details do differ, most particularly in their speed of response. AM F output saturates at Figure 13 shows the response of the devices as they are all exposed simultaneously to a sudden, upwards step-change in humidity and Figure 14 does the same for a downwards step.


It is true though that all values will be slightly biases one way or the other as conditions change. The Si is a lot slow slower than all the others, which I assume to be a deliberate design choice by the manufacturer to make the sensor insensitive to insignificant, rapid fluctuations in humidity and to better represent the wider prevailing conditions.

Contrary to the other devices though, this can occur straight out of the box, in the factory default configuration. The absolute errors were a little larger than advertised, but repeatability was good and the thermal dependence not too severe. Here I have added five new devices meaning this test now covers most commonly available low-cost digital hygrometers.

The datassheet are powered continuously, but the I2C IO lines are briefly connected to each device in turn. I am not suggesting all BMEs read hot. Front Page Kimberly Robert Hygrometers. For all the other devices the numbers above are the maximum tolerances and most also offer better ‘typical’ specifications.

The difference is small 0.

The one-wire serial of the AM is retained making this a simple drop-in replacement. Figure 5 is sodium chloride. 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 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. Left panel shows data directly from the sensors. All respond to changes faster than humidity is likely to change naturally, but speed may occaisionally by an issue of interest, for example when measuring a forced flow of air.

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