Fisher 244ER, 244EH Case Examples, Case 1 Open Sensor, Case 2 Temperature Change Greater than the

Rosemount Models 244EH and 244ER PC-Programmable Temperature Transmitters

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 (ΔT) 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.

Step Changes Greater than Threshold Value

Input

Output without Algorithm

Output with Algorithm (Default)

0 500 1000 1500 2000 2500 3000 3500 4000 Time (in Microseconds)

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.

Changes Greater than Threshold Value

Input

Output without Algorithm

Output with

Algorithm (Default)

0 500 1000 1500 2000 2500 3000 3500 4000 Time (in 500 ms increments)

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.

3-6