Datasheet SHT20 (Sensirion) - 5

link to page 5 Datasheet SHT20
2.2 Storage Conditions and Handling Instructions
second at 12bit accuracy shall be made. Moisture Sensitivity Level (MSL) is 1, according to IPC/JEDEC J-STD-020. At the same time, it is recommended to further process the sensors within 1 year after date of delivery. It is of great importance to understand that a humidity sensor is not a normal electronic component and needs to be handled with care. Chemical vapors at high
Figure 10
Top view of example of mounted SHT2x with slits concentration in combination with long exposure times milled into PCB to minimize heat transfer. may offset the sensor reading. For this reason, it is recommended to store the sensors in
2.4 Light
original packaging including the sealed ESD bag at The SHT2x is not light sensitive. Prolonged direct following conditions: Temperature shall be in the range of exposure to sunshine or strong UV radiation may age the 10°C – 50°C and humidity at 20 – 60 %RH (sensors that sensor. are not stored in ESD bags). For sensors that have been removed from the original packaging we recommend
2.5 Materials Used for Sealing / Mounting
storing them in ESD bags made of metal-in PE-HD12. Many materials absorb humidity and will act as a buffer In manufacturing and transport the sensors shall be increasing response times and hysteresis. Materials in the prevented of high concentration of chemical solvents and vicinity of the sensor must therefore be carefully chosen. long exposure times. Out-gassing of glues, adhesive tapes Recommended materials are: Any metals, LCP, POM and stickers or out-gassing packaging material such as (Delrin), PTFE (Teflon), PEEK, PP, PB, PPS, PSU, PVDF, bubble foils, foams, etc. shall be avoided. Manufacturing PVF. area shall be well ventilated. For sealing and gluing (use sparingly): Use high filled For more detailed information please consult the epoxy for electronic packaging (e.g. glob top, underfill), document “Handling Instructions” [1] or contact Sensirion. and Silicone. Out-gassing of these materials may also contaminate the sensor (see Section 2.2). Therefore, try to
2.3 Temperature Effects
add the sensor as a last manufacturing step to the Relative humidity reading strongly depends on assembly, store the assembly well ventilated after temperature. Therefore, it is essential to keep humidity manufacturing or bake at >50°C for 24 h to outgas sensors at the same temperature as the air of which the contaminants before packing. relative humidity is to be measured. In case of testing or qualification the reference sensor and test sensor must
2.6 Wiring Considerations and Signal Integrity
show equal temperature to allow for comparing humidity Carrying the SCL and SDA signal parallel and in close readings. proximity (e.g. in wires) for more than 10 cm may result in cross talk and loss of communication. This may be If the sensor shares a PCB with electronic components resolved by routing VDD and/or VSS between the two that produce heat it should be mounted in a way that SDA signals and/or using shielded cables. Furthermore, prevents heat transfer or keeps it as low as possible. slowing down SCL frequency will possibly improve signal Measures to reduce heat transfer can be ventilation, integrity. Power supply pins (VDD, VSS) must be reduction of copper layers between the sensor and the decoupled with a 100 nF capacitor – see next Section. rest of the PCB or milling a slit into the PCB around the sensor – see Figure 10. Furthermore, there are self-heating effects in case the measurement frequency is too high. To keep self-heating below 0.1°C, SHT2x should not be active for more than 10% of the time – e.g. maximum two measurements per 12 For example, 3M antistatic bag, product “1910” with zipper. www.sensirion.com Version 5 – October 2022 5/14