Omega Vehicle Security Wireless Sensor System zSeries - Manual (Page 87)

Appendix I Sensor Information (continued)
I.3 Storage Conditions and Handling Instructions
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 concentration in combination with long exposure times may offset
the sensor reading. For these reasons it is recommended to store the sensors in original
packaging including the sealed ESD bag at following conditions: Temperature shall be in the
range of 10°C – 50°C (0 – 80°C for limited time) and humidity at 20 – 60%RH (sensors that
are not stored in ESD bags). For sensors that have been removed from the original
packaging we recommend to store them in ESD bags made of PE-HD8.
In manufacturing and transport the sensors shall be prevented of high concentration of
chemical solvents and long exposure times. Out-gassing of glues, adhesive tapes and
stickers or out-gassing packaging material such as bubble foils, foams, etc. shall be avoided.
Manufacturing area shall be well ventilated.
I.4 Reconditioning Procedure
As stated above extreme conditions or exposure to solvent vapors may offset the sensor. The
following reconditioning procedure may bring the sensor back to calibration state:
Baking: 100 – 105°C at < 5%RH for 10h
Re-Hydration: 20 – 30°C at ~ 75%RH for 12h.
(75%RH can conveniently be generated with saturated NaCl solution. 100 – 105°C
correspond to 212 – 221°F, 20 – 30°C correspond to 68 – 86°F)
I.5 Temperature Effects
Relative humidity reading strongly depends on temperature. Therefore, it is essential to keep
humidity sensors at the same temperature as the air of which the relative humidity is to be
measured. In case of testing or qualification the reference sensor and test sensor must show
equal temperature to allow for comparing humidity readings.
The packaging of sensor is designed for minimal heat transfer from the pins to the sensor.
Still, if the sensor shares a PCB with electronic components that produce heat it should be
mounted in a way that prevents heat transfer or keeps it as low as possible. Furthermore,
there are self-heating effects in case the measurement frequency is too high.
I.6 Light
The sensor is not light sensitive. Prolonged direct exposure to sunshine or strong UV
radiation may age the housing.
I.7 Materials Used for Sealing / Mounting
Many materials absorb humidity and will act as a buffer increasing response times and
hysteresis. Materials in the vicinity of the sensor must therefore be carefully chosen.
Recommended materials are: Any metals, LCP, POM (Delrin), PTFE (Teflon), PE, PEEK, PP,
PB, PPS, PSU, PVDF, PVF. For sealing and gluing (use sparingly): Use high filled epoxy for
electronic packaging (e.g. glob top, underfill), and Silicone.
Out-gassing of these materials may also contaminate the sensor (see Section I.3). Therefore
try to add the sensor as a last manufacturing step to the assembly, store the assembly well
ventilated after manufacturing or bake at 50°C for 24h to outgas contaminants before
packing.
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