The sensor specification should include the maximum pet weight that will be ignored by the sensor. Indoor sensors have much less electronics in comparison with outdoor sensors that contain more than one sensor and a processor to analyse the sensor data (hence the difference in price between indoor and outdoor sensors)
a.)These sensors are usually meant for pets on the ground, a cat jumping on furniture “might” trigger the sensor.
b.) An insect or pet walking over the sensor lens “might” trigger the sensor, something that near to a sensor lens will look massive to the sensor.
c.) Two dogs for example each with a weigh of 20kg (as an example) that stand or walk very close to each other might be picked up by the sensor as one 40kg dog and be triggered.
d.) Incorrect installation will influence the pet immunity. If the manufacturer specify that the sensor should not show downwards it is because it will influence the pet immunity.