Datasheet SHT1x

www.sensirion.com

Version 5 – December 2011

4/12

following conditions: Temperature shall be in the range of

10°C – 50°C (0 – 125°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

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.

For more detailed information please consult the

document “Handling Instructions” or contact Sensirion.

1.4

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:

1.5

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.

If the SHT1x 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.

Measures to reduce heat transfer can be ventilation,

reduction of copper layers between the SHT1x and the

rest of the PCB or milling a slit into the PCB around the

sensor (see Figure 8).

Figure 8: Top view of example of mounted SHT1x with slits

milled into PCB to minimize heat transfer.

100 – 105°C correspond to 212 – 221°F, 20 – 30°C correspond to 68 – 86°F

Furthermore, there are self-heating effects in case the

measurement frequency is too high. Please refer to

Section 3.3 for detailed information.

1.6

Light

The SHT1x is not light sensitive. Prolonged direct

exposure to sunshine or strong UV radiation may age the

housing.

1.7

Membranes

SHT1x does not contain a membrane at the sensor

opening. However, a membrane may be added to prevent

dirt and droplets from entering the housing and to protect

the sensor. It will also reduce peak concentrations of

chemical vapors. For optimal response times the air

volume behind the membrane must be kept minimal.

Sensirion recommends and supplies the SF1 filter cap for

optimal IP54 protection (for higher protection – i.e. IP67 -

SF1 must be sealed to the PCB with epoxy). Please

compare Figure 9.

Figure 9:Side view of SF1 filter cap mounted between PCB and

housing wall. Volume below membrane is kept minimal.

1.8

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 SHT1x (see Section 1.3). 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.

1.9

Wiring Considerations and Signal Integrity

Carrying the SCK and DATA signal parallel and in close

proximity (e.g. in wires) for more than 10cm may result in

cross talk and loss of communication. This may be

A5Z

11

housing

PCB

o-ring

Melted plastic pin

SHT1x

membrane