Page printing



Self-excited journal whirling caused by the properties of the oil film on a fully lubricated journal bearing.
Open Collector (Contact)
Transistor contact without collector load resistance on the contact activation signal.
Output Bias
Bias added to the output signal.
Output Contact Capacity
Maximum current which can be supplied to the load while maintaining the specified performance of the voltage output equipment.
Output Current Capacity
On equipment with current output, the maximum amount of current that can be supplied to a load within a range that a certain level of performance can be maintained.
Output Impedance
Impedance included in the internal circuit of equipment when viewed from the output terminal side.
Output Resistance
Resistance component included in the internal circuit of the equipment when viewed from the output terminal side.
Outside Contact Capacity
Outside contact capacity when equipment with a built-in power supply supplies power to an outside contact and the equipment is operated by that outside contact.

Back to INDEX


Peak-to-Peak Value
The maximum algebraic difference between extreme values of vibrating quantity in the given section.
Peak Value
Maximal value in the given section.
Note: Generally, the peak value of a vibrating quantity is defined as the maximum variation from the mean value in the given section. The positive maximum variation is called the positive peak value, and the negative maximum variation is called the negative peak value.
Inverse number of frequency.
Phase Angle/Phase
Lead angle of sinusoidal quantity measured from an independent variable set as a reference.
Phase Difference
Difference between phase angles existing in two periods of equal frequency.
For a sinusoidal quantity, the difference between phase angles measured from the same reference.
Phase Marker
Rotor-shaft phase reference signal used for comparing the vibration phase of rotating machinery.
Pulse Interval
Time interval from one pulse to the next pulse.
Pulse Voltage
(1) Broadly: pulse voltage defined by the specified method.
(2) Detailed: Voltage obtained by subtracting the pulse base voltage
      (voltage below the base line) from the pulse top voltage defined by the common
Pulse Width
Duration of pulse. Unless otherwise specified, the time from the pulse rise mesial point to the pulse fall mesial point.

Back to INDEX


Degree of sharpness of resonance in a vibration system. It is defined as 2 times the ratio of energy/cycle externally applied in order to maintain a constant amplitude to energy (in a mechanical oscillating system, the sum of kinetic energy and potential energy) in the vibration system at the resonance frequency.

Back to INDEX


Random Failure
Failure accidentally occurring before the wear-out failure period following the period of initial failures.
Range between the maximum and minimum values of input or output variables.
Capability for displaying a required function of the equipment in the specified period and condition.
The maximum output difference obtained when the same input is repeatedly measured by approaching it from both directions under the same operating conditions after a fixed time.
Resistance Against Vibration
Strength against externally-applied vibration.
Note: Since the strength varies with the vibration frequency and amplitude, resistance against vibration should be expressed together with the allowable limits of frequency and amplitude or acceleration.
Resistance Load
Load consisting only of electrical resistance components.
Minimum interval between two mutually distinguishable, adjacent values.
Status or phenomenon occurring in a forced vibration system when the response lessens by slight changes in the excitation frequency in any directions.
Resonance Frequency
Frequency at which resonance occurs.
Response Time
Time required until the output signal arrives at the specified value of the final value by applying a step input signal.
Generally, the time to arrive at 90%, 95% or the final value is used, but the time to arrive at 63.2% of the final value (time constant) is used unless otherwise specified.
Note: When response time only is used, this means step response time.
Rigid Rotor
Rotor whose unbalance does not exceed the allowable error (with respect to the shaft center line) by rotor deformation, even when rotated at a speed of less than the maximum speed under the support condition close to the operating condition while balanced between two freely selected planes.
RMS Value
Root Mean Square Value.
Note: Also called effective value.
Run Out
When an eddy-current non-contact displacement sensor detects vibration and eccentricity of rotating machinery this is a measurement error caused by the rotor surface status. It is classified into mechanical runout and electrical runout.
Their causes are as follows:
For mechanical runout;
Rotor bending, uneven surface
For electrical runout;
Residual magnetic field, non-uniform material, etc.

Back to INDEX


To capture instantaneous input values at a preset time (for example, at fixed intervals).
Sampling Period
Time intervals of observation in a periodic sampling control system.
Sampling Time
Time to sense the input during sampling.
Scale Factor
Output changes per specified length in the static eddy-current displacement sensor characteristic.
Scale Factor Error
Difference between a specified sensitivity (s) and the measured scale factor expressed on percentage.
Scale Factor Error = {(SCF-s)/s} × 100[%]
Secular Change
Characteristic changes occurring in the equipment or its elements with time.
Seismic Pickup
Transducer which consists of a seismic system and generates an output signal as a result of relative motion between two elements in the seismic system.
Seismic System
System having one mass element installed via a base frame and one or more spring elements attached to the frame. Generally, damping elements are also included in this system.
Self-excited Vibration
Vibration occurring after non-vibrating energy is converted to vibration excitation in the system.
Ratio of change in quantity to be indicated to change in quantity to be measured of the equipment.
Sensitivity Error
Difference between a measured value (b) and a specified sensitivity (s) expressed on percentage.
Sensitivity Error = {(b - s)/s} × 100 [%]
SN Ratio (S/N)
(1) Ratio of noise amplitude to signal amplitude.
      Note: For a sinewave signal, the peak value or rms value is used. For a non-sinewave
      signal, the peak value is used.
(2) Ratio of signal power to noise power.
      Note: For impulse noise, the ratio of signal peak value is used.
Difference between high and low range limits.
Span Adjustment
To adjust the span of equipment to the specified value by an electrical or mechanical operation.
Span Setting
To set the span of equipment to the specified value or position by an electrical or mechanical operation.
Description of a certain quantity as a function of frequency or wave-length.
Static Characteristics
Response characteristics of the equipment with respect to the measured variable which do not change with time.
Step Response
Time response occurring when one of the input variables change stepwise.
Sub Harmonic
Sinusoidal quantity having cycles equal to an integer of 2 or more times the basic excitation cycle.
Process in which a controlled variable (generally, frequency) of a vibration generator continuously passes through a certain range.
Sweep Rate
Rate of change of a controlled variable (generally, frequency) of a vibration generator.
Example: Sweep speed = df/dt
Where, f = frequency, t = time

Back to INDEX


Temperature Drift
Drift caused by changes in the ambient temperature.
TIIS Standard
Standard defined by Technology Institution of Industrial Safety (TIIS), Japan.
Time Constant
Time required to arrive at 63.2% of the final output value in a linear 1st-order lag system by applying a step input.
(1) Time constant with time response expressed by A(1-e-t/T).
(2) In a higher-order lag system, each 1st order lag element in a process has a time constant.
      The corner frequency is expressed by ω = 1/T in the Bode diagram.
Time Response
Time changes in the output variable caused by changes in the input variable.
Torsional Vibration
Vibration which occurs as torsional changes of a rigid body.
Transfer Function
Arithmetic relationship between the output and input in a system.
Note: Generally, the transfer function is given as a function of the frequency and is a function of a complex variable.
Transient Response
Time required until an output (signal) returns to steady state when an input (signal) changes to another steady state.
Transmission Distance
Length of an electrical conductor that can transmit signals accurately at a required transmission speed.
Note: Transmission distance is decided based on the conditions including impedances of electrical conductor, device specific input/output characteristics, external noises, property of the measurement system, etc.
Transverse Sensitivity
Sensitivity of excitation in any direction at right angles to the sensing shaft.
Note: This is a function of the excitation direction.
Trigger Voltage
Pulse voltage to trigger rapid changes in status or output of an electronic circuit.

Back to INDEX


Rotor status of producing a vibration forcer or motion on the shaft as a result of centrifugal force.
Note: Sometimes used as a synonym for the size of unbalance or the vector of unbalance.
Unbalance Mass
Mass considered to exist in the specific radius position and whose product with centripetal acceleration becomes equal to the unbalance force.
Unbalance Tolerance
Size of rigid-rotor shaft unbalance defined as the tolerable maximum value within a plane at right angles to the shaft (corrected or measured surface).
Undamped Natural Frequency
Frequency of free vibration generated only by system inertia and elastic force.
Note: Simply called natural frequency, if this does not cause confusion.

Back to INDEX

Terms for measurement:
JIS Z8103
Terms for performance of industrial instruments:
Japan Electrical Measuring Instrument
Industry Association
Vibration Engineering Handbook:
Terms for electronic measuring instrument:
Japan Electrical Measuring Instrument
Industry Association

TEL:81-3-3263-4411 FAX:81-3-3262-2171

  • Contact
  • Estimate

Customer Support

  • CMS Condition Monitoring System
  • SHINKAWA's Strength
  • Tech Column
  • Request for Quotation
  • CMS Video Guides
  • Movie
  • Downloadable Documents
  • Glossary
  • Development

Seminar Information

To page top