Accuracy; Facts To Consider Regarding Accuracy - SKF Multilog On-Line System IMx-M User Manual

Protection

Accuracy

Accuracy

Facts to Consider Regarding Accuracy


Protection modules (PRM) and condition monitoring modules (CMM) can show
different values due to the following reasons.
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
API 670 specifies ±1% and ±0,5 dB filters in passband which leads to ±6% in total.

Calibration of reference instruments does not mean it is exact. It only means that it
is within the specification.

Note that most reference instruments are not accurate for low frequencies below
50 Hz.

The following diagram shows an example of same or different readings for PRM
and CMM depending on the input signal frequency in conjunction with filters.
2 - 2
They are two separate individual measurement devices.
They have two different purposes. PRM is to optimize the quick response time
as defined in API 670 whereas CMM is to optimize the early fault detection.
They use two different measurement algorithms.
They have two different filter setups.
Figure 2 - 1.
Comparison of PRM and CMM Readings.
SKF Multilog On-Line System IMx-M
User Manual