We are designing an STHS34PF80 into an occupancy sensor and the plan is to have an HDPE window to protect it. To test the response in the actual product we purchased 1/16" (1.5mm) HDPE sheet and put it over the sensor. The fresnel lens with the dev kit was removed. Surprisingly the Tpresence triggers when the sheet is over the sensor, and so the device doesn't seem to be seeing through the HDPE sheet.
My first thought is that the HDPE is doped or just wrong somehow but I thought I'd ask if anybody else has seen something like this.
Thank you.
