The board has 2 functions, 1.-Provides the momentary switch to activate the calibration function (looks like the sensor "remembers" this setting), and 2.-Has some filter capacitors in all lines (+5, pulse out, calibration)
Can you provide a link to the product you bought? Taobao seems to be a chinesse page but maybe by the product name I can find your product on another provider that's closer to me
The container I will be using is plastic
Thanks!