Fisher Weather Radio 244ER User Manual

3-6

If the algorithm detects an open sensor, the transmitter immediately 
goes into alarm (high or low, depending on the position of the failure 
mode switch).

If the algorithm detects a process temperature change (

∆

T) greater 

than the threshold value (2 % of the output range), but which is not a 
true open sensor condition, the transmitter will go into a hold period. 
During the hold period, the transmitter determines whether or not this 
temperature measurement is valid by using the three additional 
measurement points. In the meantime, the output remains unchanged 
at the initial reading (Time = 0 ms).

A) If these next three readings are within the new threshold value 
(at Time = 500 ms), this measurement is validated. The output 
changes to reflect this and the transmitter is no longer in a hold 
period. In this case, the output delay is 1.75 to 2.00 seconds.

B) If the reading drops back within the original threshold value (at 
Time = 0 ms) during the hold period, the transmitter interprets the 
reading(s) outside the threshold value as a spike, and the output 
changes to reflect the latest reading. The transmitter is no longer in 
a hold period, and the spike is not seen at the output.

C) If any of the next three measurements is outside the new 
threshold value (at Time = 500 ms), the output remains unchanged 
at the initial reading (Time = 0 ms). the transmitter remains in a 
hold period until four consecutive measurements are within the 
threshold value of the first in the series.