TM 5-3895-374-24-2
955-257
10) Using the oscillation time measured in Step 7, calculate the value for RESET in repeats per minutes as follows:
RESET = 8 X 1 ; Where To = Oscillation Time in Minutes.
5
To
Or use Nomogram II below:
NOMOGRAM II
Enter this value for RESET 1.
11) Again using the oscillation time measured in Step 7, calculate the value for RATE in minutes as follows:
To
RATE = To : Where To-Oscillation Time in Minutes
10
Or use Nomogram III below and enter this value for RATE 1.
TEMPERATURE CYCLE TIME IN MINUTES
NOMOGRAM III
12) If overshoot occurred, it can be eliminated by decreasing the RESET time. When changes are made in the RESET
value, a corresponding change should also be made in the RATE adjustment so that the RATE value is equal to:
RATE =
1
i.e., If reset = 2 R/M then
6 X Reset Value
Rate equals 0.08 Min.
13) Several setpoint changes and consequent RESET and RATE time adjustments may be required to obtain the proper
balance between "RESPONSE TIME" to a system upset and "SETTLING TIME". In general, fast response is
accompanied by larger overshoot and consequently shorter time for the process to "SETTLE OUT". Conversely, it the
response is slower, the process tends to slide into the final value with little or no overshoot. The requirements of the
system dictate which action is desired.
14) When satisfactory tuning has been achieved, the cycle time should be increased to save contactor life (applies to units
with time proportioning outputs only TPR). Increase the cycle time as much as possible without causing oscillations in
the measurement due to load cycling.
ECLIPSE INSTRUMENTATION DIVISION
page 3-1101
