All trademarks are the property of their respective owners.
Figure 1-1 shows two standard humidity sensor components whose sensing elements are exposed on the top (HDC2080) and on the bottom (HDC2010). These sensors have integrated ADCs and are designed to accurately and reliably measure and output the percentage relative humidity (%RH) and temperature data on an I2C-bus.
The capacitive sensing element is composed of a moisture-sensitive polymer as a dielectric and comb metal structure as the capacitance’s electrodes. A change in humidity correlates with the capacitance change with the entire sensing element structure is integrated on a top layer of a standard CMOS technology process. The capacitance value is converted to analog output voltage that is fed to the ADC and the proprietary linearization engine, and as a result, the percent RH value is computed and output is consistent, predictable, and accurate.
The sensor dielectric’s polymer is generally dust resistant and excellent for any normal environmental sensing application imaginable. As always with an exposed cavity, care must be taken during the assembly process because the polymer can be damaged by chemical or assembly cleaning and the scrubbing process.
Humidity sensors require additional storage and handling guidelines that must be followed. More information is available in our HDC20xx Silicon User's Guide.
A removable protective cover is a thin polyimide tape that covers over the entire surface of the humidity sensing component. It is a shield for temporary protection of the sensing element from contaminants, and should be removed before being used. This cover can protect against pollution during the PCB cleaning and scrubbing process, hence allowing this component to go through a normal PCB wash process without damaging the sensor.
This protective cover also protects the sensor during a conformal coating or potting for such application as a humidity module where other components and PCB solder joints need to be shielded from long term harsh environmental exposure. The protective cover is robust and designed to withstand multiple reflow soldering cycles. It comes with an adhesive-free tab that is easily peeled off at the end of the assembly process, by either using tweezers or another piece of polyimide tape. Figure 1-4 depicts a humidity sensor with a removable protective cover, the HDC2021, which is pin- and software- compatible with the HDC2080.