Machine Health Monitoring (MHM) / 機器健康監測
Machine Health Monitoring provides efficient methods by reducing downtime and
preserving assets. Vibration monitoring will enable preventive maintenance on
almost any type of machine. It could be done by recurrent control or real time
analysis. Condition monitoring involves fixing sensors to mechanical parts of
the machines in order to track failures and malfunctions.
Imbalance, external vibrations, oil-whirl
Hz – 100 Hz
Imbalance, hunting mesh, misalignment, looseness
Hz – 1’000 Hz
faults, gear pitting, shocks
– 100’000 Hz
Low frequency monitoring (from DC 0 Hz to 1000 Hz) includes:
• Hunting tooth detection
• Low speed fan monitoring in cooling towers
• Low speed agitators in industries
• Geophysical measurement equipment
Explanation of the System
MHM will be set up according to the type of faults to analyze, by measuring
frequency ranges. In general, spectrum analysis is used to identify the
different vibration frequencies.
MHM requires reliable sensors, resistant to possibly high temperature and
repetitive shocks. The system must be able to operate in wet and corrosive
environments (e.g. in a cooling tower). Furthermore, the sensors must last as
long as the component analyzed.
Monitoring at low frequencies implies two major requirements. First of all, the
noise produced by the sensor must be as low as possible: the least amount of
electronic noise generated, the quicker a fault is detected. As an example,
specific CNC machines require sensors with a noise level between 75 and 90 dB,
operating at a low frequency (DC 0 Hz – 1’000 Hz). Secondly, a high voltage
output is key to set a sufficient threshold.
The vibration sensors are
accommodated for this application, particularly the VS1000
series. The good ranges of measurement would be ±2g, ±5g and ±10g. The
VS1002 sensor’s property is its very low noise level of 7 µg/√Hz – equivalent to
class C at 90 dB. The VS1000 sensors have a non-linearity of 0.1% (typ. full
scale), a linear frequency response from DC 0 Hz to 2500 Hz at ±5% FS, up to
7000 Hz at -3 dB. A maximum shock resistance of 6000g ensure a strong
survivability of the sensors.