Frequently Asked Questions

A Piezo sensor might show reverse polarity signals in two scenarios: 

1) If it is not tight over the body while pressed under the body, and it was not calibrated for same phase response for tension and compression.  SleepSense Piezo Crystal Sensors produce the same polarity for tension and compression, so this will not happen.

2) If respiration rate is very low, so that the signal decays long before the chest resumes exhale position.  This might happen if the sensor's time constant is too short for accurate replication of slow respiration.  SleepSense Piezo Crystal Sensors have the longest time constant, so this will almost never happen.