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6.7
Differential speed detection
6.7.1
Differential speed detection (P040)
Differential Speed Detection (DSD) function, provides a relay output based on differential
comparison between probes A and C, B and D. Enable for DSD use, disable for standard speed
monitoring. The DSD can be enabled from this display. Pressing the F2 or Esc Key & ▲ cursor
key together will enable or disable this feature set.
Note
Standard operating setpoints must be programmed between 1 to 10% only. A setpoint of 0%
(which can be set by user interface) will result in an alarm condition, Q3 or Q4 set to failsafe
(Lo level)
DSD Calibration
The DSD must be calibrated so that each input has a full scale reading that is proportional to
the maximum operating speed of the machinery. The maximum input frequency for each
input is 5000 Hz. In DSD mode, the two calibrated inputs are compared to each other and if
the differential is greater than the set point, it will go into alarm.
For example:
1 Hz on a 1000 Hz full scale is equal to 0.1% speed change.
1 Hz on a 100 Hz full scale is equal to 1% speed change.
1 Hz on a 10 Hz full scale is equal to a 10% speed change.
Note
The input resolution is 1 Hz. Depending on the Input frequency calibration, this 1 Hz value
will represent a different percentage of speed change.
• P040: Enabled or Disabled
SITRANS WM300 MFA
Operating Instructions, 11/2021, A5E45090709-AC
Parameter assignment
6.7 Differential speed detection
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