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Rosemount Models 244EH and 244ER PC-Programmable Temperature Transmitters
3-6
Case Examples Case 1: Open Sensor
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).
Case 2: Temperature Change Greater than the
Threshold Value(2% of Output Range)
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.
0 500 1000 1500 2000 2500 3000 3500 4000
Step Changes Greater than Threshold Value
Input
Time (in Microseconds)
Output without Algorithm
Output with Algorithm (Default)
0 500 1000 1500 2000 25003000 3500 4000
Changes Greater than Threshold Value
Input
Time (in 500 ms increments)
Output without Algorithm
Output with
Algorithm (Default)