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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Currently I am attributing it to bad luck in my getting a couple of faulty devices rather than a systematic fault with this model. Plots showing datasheef deviation of humidity values from the known reference value. It has been datasheef out into a separate document since rendering nine surfaces simultaneously proved an excessive load for some web browsers. 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.
Most of the others seem comparable to each other except the Si which is the dataseet major outlier. However, investigating in more detail, the Bosch thermometers are very weakly humidity sensitive.
Though I designed and integrated the entire experiment, I must acknowledge the many open source projects, both software and hardware, that I used.
AM Datasheet PDF –
As far as I have been able to acertain, all the other devices are polymer capacitance hygrometers. Pin Identification and Configuration No: It seems well made and has not yet shown any problems in well over two years of continuous operation.
The word is derived from ancient greek for ‘lagging behind’. As previously noted, this is my cherry-picked, best AM from a sample of six. 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.
The absolute errors were a little larger than advertised, but repeatability was good and the thermal dependence not too severe.
DHT22 Sensor Pinout, Specs, Equivalents, Circuit & Datasheet
I am not suggesting all BMEs read hot. This data pin outputs the value of both temperature and humidity as serial data. Either way the performance of the sensor datasheeg same. 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 datashret permanently biased by its history and would never reach the same ‘true’ value when approaching from above or below.
Figure 5 is sodium chloride. Though equivalent for most normal use, the precise specification details do differ, most particularly in their speed of response. In contrast, the AM device G shows little error as a function of humidity Figure 12 a2m302 has the largest error as a function of temperature Figure Submitted by admin on 19 April Blue shows low readings and red are high. As expected, all sensors do show the tendency to read systematically high when the humidity is decreasing and read low when humidity is rising.
Apart from that linear tilt in the temperature: Though an interesting addition and I will write about it elsewhere, for the present report I present only the temperature datashest humidity data. The other six are new and this is their first test.
These same data are presented in more detail in Figure 4. However, for all devices except the Si and AM the effect is small and the satasheet of the envelope is not larger than the scatter of data points already observed. Almost vaguely related and possibly of interest is monitoring radon in the house.
Be careful with variable types in your software. Each of these three sensors showed advantages in one paramter ddatasheet 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. Similarly the Sensirion SHT21 not included here also has a near identical specification and interface.
Surfaces showing deviation of each sensor from the true relative humidity as a function of temperature and humidity. See ‘Update March ‘ above. Also commonly known as DHT 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.
(PDF) AM2302 Datasheet download
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.
Contrary to the other devices though, this can occur straight out of the box, in the factory default configuration. The humidity axis has been set to the same range in all three plots in order to fairly represent the relative gradients of the datawheet.
I never found a cause or have any suggestion for why dztasheet should fail to produce output in such a narrow range of humidity. For most sensors the traces followed on rising and falling humidity are reasonably close together, showing little hysteresis bias. Comparison of the packaging of the various devices. Plots showing deviation of each device’s own temperature from the average of all nine, plotted as a function of datasehet.
My Si is arguably the poorest of am232 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. The difference is so stark that it leads me to believe the sensing element is in some way fundamentally different from the other devices. The Si is a lot slow slower than all the others, which I assume to be datashete 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.
Sensors were allowed to stabilise for a few hours with each solution. Repeatability at a fixed humidity is very dtaasheet.
The same device as was used in previous tests. Plots show temperature returned by each device compared to the average of all nine.
AM2302 Datasheet PDF
This run confirms my datssheet experiments with this device. Though primarily interested in humidity, I present a brief comparison of the temperature measurements. There is some suggestion from the manufacturer’s web site that this might already be discontinued and replaced by AM The AM appears to be the same but in a much smaller physical package and narrower pin pitch. It was only by reading the internal serial numbers I was able to ascertain that.