TRAKKER, Inc. manufactures four vibration sensors;
1500Hz
This sensor is designed to track Vibration (noise) levels that are generated by devices that generally have a low signature, i.e. hydraulic pumps, hydraulic motors, gear boxes, presses, forming equipment, piston pumps, extrusion pumps and screws, wind generation equipment, blade distortion in air movement devices, motor coupling, and alignment issues between motors, gears, and pumps.
This device tracks the movement in two planes and generates an output signal that is the average of the X and Y movement of the device. This average is produced in the following manner - every 200 ns and the Smart Board, Hound, or OWL records the "average*" of 16 samples, stores that data and begins to generate another 16 sample "average*", and replaces the previous "average*" that is in storage with the current "averaged*" number and the process repeats itself as long as the system is operating.
The computer then requests the most current stored "average" from the Smart Board, Hound, or OWL every 200 mgRMS and logs the incoming data as determined by the particular operator (every min, every 5 min, every 10, etc) and the TRAKKER operating system then:
- A) does nothing with the data,
- B) compares the data to historic data that is in storage in a TRAKKER reference file,
- C) compares that data to a baseline number that was generated when the device was first put in service,
- D) uses that data to complete some algorithm and stores the product of the algorithm at intervals as determined (every min, every 5 min, every 10, etc).
An example of an algorithm is as follows: there is a gang saw on the third level (floor) of a saw mill that is hard fastened to a common steel platform that has mechanical devices on each of the three floors and generates the following:
- When the gang saw is operating it outputs a vibration signal of .472 mgRMS to .568 mgRMS.
- This vibration generates a signal down through the steel platform of .250 mgRMS to .285 mgRMS in what is referred to as "platform noise".
- Is a planner mill on the second floor 250 feet away on the second level of the steel platform that generates a vibration signal of .355 mgRMS to .395 mgRMS, and
- when the planner is running it produces a signal in the steel platform of .185 mgRMS to .210 mgRMS ("platform noise").
- If both the gang saw and the planner mill are operating then the net floor vibration approximates .435 mgRMS (.250 + .185) and .495 mgRMS (.285 + .210), and the
- Gang saw vibration moves up to .657 mgRMS to .778 mgRMS and the planner mill vibration signal moves up to .540 mgRMS up to .605 mgRMS.
- Therefore the algorithm is set to produce the following result:
- subtract the historic average of the platform noise when the gang saw is running (.250 + .285)/2 = .2675 from the current platform sample and then subtract that noise from the current gang saw vibration number and log that number
- If the gang saw is running and the planner is not, then essentially 0 is subtracted from the gang saw vibration signal, and conversely
- If the planner is running and the gang saw is not then the algorithm will essentially subtract 0 from the planner vibration number, however,
- If both are running then there are two concurrent algorithms that zero out the platform noise generated by each device from the vibration signal of the other device.
The TRAKKER system will log both the raw analog data and the product of any of the algorithm for future reference.
The data is transmitted in analog form from the sensor and is communicated to the PC from the Smart Board, Hound, or OWL in 485 form (ones and zeros).
10 to 1000Hz
This sensor is designed to track a more complicated device or apparatus that produces a variety of signals over a range that is between 10 Hz and 1000 Hz. This device tracks the movement in three planes and generates an output signal for all three axis, i.e. X, Y, and Z.
This sensor transmits the data in analog form to an on-board processor (chip) that converts the vibration data from analog to digital in the form of a 485 signal. The signal is divided into 1024 packets that are each approximately .878Hz in range and the processor on the Hound or OWL forwards that information to the PC in 485 form. The PC then logs the packet data, as determined (every min, every 5 min, every 10, etc). the TRAKKER system then examines the data in groups of 100 packets (100 packets of .878 Hz each = 87Hz ea) for anomalies or variations by comparison to either historic data stored in the TRAKKER operating system or manufacture's data, startup data, or as determined by the customer.
The on-board processor also completes a series of algorithms for each of the three axis:
| Reading | Formula |
|---|---|
| Acceleration Peak since last reading X, Y, Z, & A (A = average) | where A =  |
| RMS acceleration (pos values only {PVS}) X, Y, Z, & A | where A = |
| RMS acceleration peak since last reading (PVS) X, Y, Z, & A | where A = |
| RMS velocity (PVS) X, Y, Z, & A | where A = |
| RMS velocity peak Since last reading (PVS) X, Y, Z, & A | where A = |
10 to 10,000Hz
This sensor is designed to track a more complicated device or apparatus that produces a variety of signals over a range that is between 10 Hz and 10,000 Hz. This device tracks the movement in three planes and generates an output signal for all three axis, i.e. X, Y, and Z. This device is most effectively used in a circumstance that involves a device that is generating a low noise (slow movement) that is hard coupled to a device (gearbox) that translates the slow movement to a device that is operating at high speeds and generates a much higher frequency. Generally a low speed (steel) bearing to a high speed (ceramic) bearing circumstance that is coupled so closely that the low noise cannot be segregated or isolated from the high frequency noise.
This sensor transmits the data in analog form to an on-board processor (chip) that converts the vibration data from analog to digital in the form of a 485 signal. The signal is divided into 1024 packets that are each approximately 9.75Hz in range and the processor on the Hound or OWL forwards that information to the PC in 485 form. The PC then logs the packet data, as determined (every min, every 5 min, every 10, etc). The TRAKKER system then examines the data (in groups of 20 packets or as determined) for anomalies or variations by comparison to either historic data stored in the TRAKKER operating system or manufacture's data, startup data, or as determined by the customer.
The on-board processor also completes a series of algorithms for each of the three axis:
| Reading | Formula |
|---|---|
| Acceleration Peak since last reading X, Y, Z, & A (A = average) | where A = |
| RMS acceleration (pos values only {PVS}) X, Y, Z, & A | where A = |
| RMS acceleration peak since last reading (PVS) X, Y, Z, & A | where A = |
| RMS velocity (PVS) X, Y, Z, & A | where A = |
| RMS velocity peak Since last reading (PVS) X, Y, Z, & A | where A = |
10 to 20,000Hz
This sensor is designed to track a more complicated device or apparatus that produces a variety of signals over a range that is between 10 Hz and 10,000 Hz. This device tracks the movement in three planes and generates an output signal for all three axis, i.e. X, Y, and Z. This device is most effectively used in a circumstance that involves a device that is generating a low noise (slow movement) that is hard coupled to a device (gearbox) that translates the slow movement to a device that is operating at high speeds and generates a much higher frequency. Generally a low speed (steel) bearing to a high speed (ceramic) bearing circumstance that is coupled so closely that the low noise cannot be segregated or isolated from the high frequency noise.
This sensor transmits the data in analog form to an on-board processor (chip) that converts the vibration data from analog to digital in the form of a 485 signal. The signal is divided into 1024 packets that are each approximately 19.5Hz in range and the processor on the Hound or OWL forwards that information to the PC in 485 form. The PC then logs the packet data, as determined (every min, every 5 min, every 10, etc). The TRAKKER system then examines the data (in groups of 10 packets or as determined ) for anomalies or variations by comparison to either historic data stored in the TRAKKER operating system or manufacture's data, startup data, or as determined by the customer.
The on-board processor also completes a series of algorithms for each of the three axis:
| Reading | Formula |
|---|---|
| Acceleration Peak since last reading X, Y, Z, & A (A = average) | where A = |
| RMS acceleration (pos values only {PVS}) X, Y, Z, & A | where A = |
| RMS acceleration peak since last reading (PVS) X, Y, Z, & A | where A = |
| RMS velocity (PVS) X, Y, Z, & A | where A = |
| RMS velocity peak Since last reading (PVS) X, Y, Z, & A | where A = |
* The measurement that is given as the result of the vibration analysis of a particular device or component is the movement of that object relative to some time frame, i.e. meters/second2 = m/s2. However, the standard output for most vibration sensors is measured in "g" or "mg" and would generally be on the order of 0g to 500g when 1 g is assumed to be 9.81 m/s2.
Definition:
The meter per second squared is the SI derived unit of acceleration. It is a measure of magnitude and can be a scalar measure or, when associated with a direction, a vector. The unit is written in symbols as m/s2, m•s−2, or m s−2. It may be better understood when phrased as "metre per second per second"; in other words, the increase in speed (in metres per second) that is achieved each second. To further clarify this, one meter per second squared means that, if an object is accelerating at 1 m/s2 from rest, it will after 5 seconds have a speed of 5 m/s speed (etc.) accordingly.
The actual output of the acceleration of an object may be measured in a number of other terms, many of which are not familiar to most of folks. Example the TRAKKER 1500Hz has an accelerometer range of .005g to 1.7g. When I grew up g = gram, or g= gravitational pull or force as in the pilot was subjected to __g in that particular maneuver.
The symbol g in the vibration analysis world is not to be confused with either grams or gravity, and has the following meaning:
The g-force on something is its acceleration relative to free-fall. This acceleration experienced by an object is due to the unopposed non-gravitational force acting per unit of the object's mass. It is termed a "force" because such proper accelerations cannot be produced by gravity itself, but instead must result from other types of forces which cause stresses and strains on objects which can make these sorts of forces significant. Because of these strains, sufficiently large g-forces may be highly destructive to objects and organisms.
Vibration for the TRAKKER vibration sensors is actually an output signal that provides the following information: the actual power that is acting on an object at a given sample point and the unit of measure is "mg" and is derived in the following fashion:
The metric of Grms is typically used to specify and compare the energy in repetitive shock vibration systems. However, the method of arriving at the Grms measurement (input signal filtering, cutoff frequency of the measurement) can have a dramatic effect on the value. It is important to understand how the measurement is made, and to understand its limitations, in order to use it effectively. This paper will describe the metric of Grms, how it is calculated in both the frequency and time domains and what factors can cause variations in Grms calculations.
What is Grms? Repetitive shock (RS) vibration systems produce a continuously varying pseudorandom broad spectrum vibration. A typical real time signal from an accelerometer mounted on an RS table is shown in figure 1. The root mean square (rms) value of this signal can be calculated by squaring the magnitude of the signal at every point, finding the average (mean) value of the squared magnitude, then taking the square root of the average value. The resulting number is the Grms metric. (Note: Since this paper addresses Grms calculations specifically, all of the discussion here assumes a signal source that is representative of g's (acceleration). However, the discussion would apply equally well to any measured signal.) "Neill Doertenbach of QualMark Corp."
In the final analysis, the meaning of a vibration number produced by a particular object is a subjective product. The mgRMS of .285 that may be produced by a 2 Hp fan motor is certainly not the same product as the mgRMS signal produced by a 250 ton press. Therefore, when analyzing the output data and/or logged data from the TRAKKER vibration sensors, it is important to compare like devices, when possible, or to use baseline manufacturer's data as the reference point. The vibration signal that is derived from a 2 Hp to 15 Hp motor and associated coupling/gearbox will certainly not be relevant to the analysis of a 400 Hp motor and associated coupling or associated gearbox.
Consider: a particular bearing, motor, gearbox, etc may have a vibration signal when the manufacture is testing the device before shipment of .125 mgRMS. However, since bearings, motors, gearboxes, etc are always attached in some manner or fashion to other devices, the standalone number is of very little value in determining the life expectancy at any particular time or in any give industrial or commercial deployment