Basement This unit is on the floor of the basement office, on a short leash to the server running ham radio software. The sensor is mounted in the mini prototyping socket first used to test 1-wire devices. This sensor is the reference to which we compare new sensors when we add them to our sensor network. New sensors are placed in the socket next to this sensor and observed for several hours, long enough to notice first-order differences.
Upstairs bias: -0.27 This sensor is mouned on the side of my bedroom nightstand. It is close to an outside wall.
Backyard This unit is placed outside the basement window at the end of a steel tube that holds the sensor several feet away from the house.
Main This unit is mounted on the first step of the stairs behind my favorite chair. bias: 0.05
Daylight Here we have a CdS photocell measuring the light level in the basement. Rather than use the one-wire mechanism, here we use a dedicated Arduino at the sensor and communicate back to the data recording through http protocol.
See also day to day Twilight Drift as days get longer or shorter.