Datasheet

DHT20 Data Sheet
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Version:V1.0 —— May 2021
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4.2 Storage Conditions and Operating Instructions
The level of the humidity sensitivity (MSL) is 1, according to the IPC/JEDEC J-STD-020 standard. Therefore, it is
recommended to use it within one year after shipment.
This kind of the sensor is not an ordinary electronic component and needs to be carefully protected. Users must
pay more attention to this key point. Long-term exposure to high concentrations of chemical vapor will cause the
output signal of the sensor drift. Therefore, it is recommended to store the sensor in the original packaging including
a sealed ESD bag, and meet the following conditions: temperature range 10
℃
- 50
℃
(a limited time within 0-
85
℃
); humidity 20-60%RH (the sensor without ESD package). For those sensors which had been removed from
the original packaging, we recommend to store them in an antistatic bag made of PET/AL/CPE containing metal.
During production and transportation, the sensor should be avoided to contact with high concentrations of chemical
solvents and long-term exposure in the air. It is should to avoid to contact with volatile glues, tapes, stickers or
volatile packaging materials, such as foam foils and foam materials, etc. The area of production should be well
ventilated.
4.3 Recovery Processing
As mentioned above, if the sensor had been exposed to extreme working conditions or chemical vapors, the output
signal will drift. It can be restored to the calibration state by the following processing.
Drying: Keep for 6 hours under 60-65℃ and <5%RH humidity conditions;
Rehydration: Keep for 6 hours under 20-30℃ and >75%RH humidity conditions
7
.
4.4 Temperature Effect
The relative humidity of the gas depends to a large extent on the temperature. Therefore, it is necessary to ensure
that all sensors measuring the same humidity operate at the same condition of temperature. It should to make sure
that the tested sensor and the reference sensor are at the same conditions when operate the test, and then
compare the output signals.
In addition, when the measurement is at high frequency, the temperature of the sensor will rise, so it will affect the
accuracy. If you want to ensure the variation of the temperature of the sensor is less than 0.1°C, the activation time
of DHT20 should not exceed 10% of the measurement time. It is recommended to measure the data every 2
seconds.
4.5 Materials for Sealing and Encapsulation
Many materials can absorb moisture and will act as a buffer, which will increase the time of response and lag.
Therefore, the materials around the sensors should be carefully selected. The recommended materials are: metal
materials, LCP, POM(Delrin), PTFE(Teflon), PE, PEEK, PP, PB, PPS, PSU, PVDF, PVF.
Material used for sealing and bonding (conservative recommendation): It is recommended to use epoxy resin or
silicone resin to encapsulate electronic components. The gases released by these materials may also contaminate
DHT20 (see 4.2). Therefore, the sensor should be assembled last, and stored in a well-ventilated place, or dried for
24 hours in an environment of >50
℃
, so as to release the polluted gas before packaging.
4.6 Wiring Rules and Signal Integrity
If the signal lines of SCL and SDA are parallel and very close to each other, it may cause signal crosstalk and
communication failure. The solution is to place VDD and/or GND between the two signal lines, separate the signal
lines, and use shielded cables. In addition, reduce SCL frequency may also improve the integrity of signal
transmission. A 100nF decoupling capacitor must be added between the power supply pins (VDD, GND) for filtering.
This capacitor should be as close as possible to the sensor. See the next chapter.
7.
75%RH can be easily generated from saturated NaCl.