Question

Provide links to websites for the most accurate and cheapest sensors to be able to be placed under a table to sense if something is under a table.

(eg. IR (TCRT5000L):

https://www.aliexpress.com/item/10-Pcs-TCRT5000L-TCRT5000-Reflective-Optical-Sensor-Infrared-IR-Photoelectric-Switch/32841460175.html?src=google&albslr=221466033&isdl=y&aff_short_key=UneMJZVf&source=%7Bifdyn:dyn%7D%7Bifpla:pla%7D%7Bifdbm:DBM&albch=DID%7D&src=google&albch=shopping&acnt=708-803-3821&isdl=y&albcp=653153647&albag=34728528644&slnk=&trgt=61865531738&plac=&crea=en32841460175&netw=g&device=c&mtctp=&gclid=EAIaIQobChMI6KTozJHn2AIVmMBkCh25ywtLEAkYAiABEgKhUfD_BwE or

sonar:

https://www.ebay.com/p/5x-Ultrasonic-Module-Hc-sr04-Distance-Transducer-Sensor-for-Robot/27005447895?iid=122599717234)

This is for a project to stop a table from lowering and crushing an object if it is under the table top.

Answer 1

https://www.amazon.in/Triple-Axis-Accelerometer-ADXL335-Robokart/dp/B011KPYAUE?tag=googinhydr18418-21&tag=googinkenshoo-21&ascsubtag=3c3b24fb-0448-4e2e-9d4e-0f0cb7128443

you can purchase accelerometer based sensor which works in all the three coordinates such that if any small vibration occurs then also it responds (i.e. it is very accurate and precise). lots of variety are available in Amazon where u can select your suitable product. i have already used accelerometer based sensor in my project which sense pulse beats from outside.