Measurement Definitions

Accuracy
The accuracy of a measurement system is the degree of closeness of measurements of some quantity to its actual (or true) value.  (© Wikipedia®)

Repeatability
The precision of a measurement system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same result.  (
© Wikipedia®)

Absolute Technology      
Our Capacitive Absolute encoder technology (ABS) has been in production since 1997.  Absolute Technology measures the actual sensor position by reading a pattern which is unique at any given location over its length (approximately 17 inches).  This results in a measuring system with a high immunity to loss of position due to motor electrical noise, power transients, or magnetic fields.
There is no position loss when the digital readout is turned off, or when power is interrupted.
ABS technology is still used in many of our products.

Inductive Series II Technology       
Our Inductive Series II Incremental measuring technology began production in June 2013.  This technology, and the systems manufactured using it, are direct (mechanical) replacements for earlier Series I systems.  Series II is more robust technology than Series I.  Its signal is more immune to power transients, magnetic fields, and ESD. Plus, the slew (movement rate) is greatly increased. Series II technology is used in ProScale Models 190, 290, 390 and 590 as well as many of the turn-key measuring systems we manufacture incorporating these models.

Inductive Series I Technology       
Our Inductive Series I Incremental measuring technology has been in production since the 2007.  Inductive measuring technology measures the distance it has traveled relative to a starting point. It is however a much more robust technology than the Capacitive Incremental technology we used previous to 2007.  Its signal is more immune to electrical motor EMI, power transients, magnetic fields, static, so the position information is not lost as easily as the older technology.  Inductive Series I production ended in June 2013.
Products using this technology are no longer manufactured.

Capacitive Incremental Technology     
Our Capacitive Incremental measuring technology has been in use since 1989.  Incremental technology measures the distance it has traveled relative to a starting point. As long as the signal is not reset or interrupted (by removal of batteries, electrical motor EMI, power transients, magnetic fields, static, etc.), the position information is not lost.  Incremental technology was used in all of the measuring systems we manufactured until 1997. We began to phase out this technology in favor or more advanced Inductive Technology in 2007, and production was ended in 2009. Products using this technology are no longer available.

Absolute Measurement:
An absolute measurement is the distance from some fixed position.  On a table saw, this is typically the distance from the right edge of table saw blade.  For the best accuracy, this is the distance from the right edge of the running blade - accounting for any variance of blade flatness, or bearing run-out. The absolute distance can be set to zero, or to any other offset, quickly and easily using the readout keypad.  The absolute distance is retained when the readout is turned off or switched into INCremental measuring mode.

Incremental Measurement:
An incremental measurement is the distance from a current (absolute) position.  On a table saw, this could be the distance between dados or grooves. It could also be the distance from the left edge of the saw blade.  The incremental distance can be set to zero, or to any other offset, quickly and easily using the readout keypad.  Changing between Absolute and Incremental modes is easily done by pressing a single key.  The incremental distance is retained when the readouts power is off.

SPC
Statistical Process Control is a tool that businesses and industries use to achieve quality in their products and/or services.
By monitoring the accuracy, or in-tolerance percentage of manufactured products, and collecting current measurement data from measuring devices, a company can adjust their processes and machines to produce better products, faster
Most of our measuring products may be integrated into a company's SPC program by use of serial connection to a computer or printer.
This serial connection uses the format called Mitutoyo Digimatic
® for the transmission of measured values or positions. Our encoders carry this signal to our digital readouts.  Many of our digital readouts also have a 10-pin output connector which can be used to transmit the currently displayed reading. 
These signals may be gathered using Gageway or ProMux, or transmitted wirelessly using our ProRF products.

RoHS Compliance

The RoHS directive aims to restrict certain dangerous substances used in electronic equipment. Any RoHS compliant component is tested for the presence of Lead (Pb).  There must be no more than 0.1%. And, any RoHS compliant component must have 100 ppm or less of mercury.

Abbé Error
Abbe error is a condition that may not be visible to the human eye, but will affect linear measurements. Be sure to take precautions when installing ProScale in order to eliminate the possibility for Abbe error.

 
Abbe error refers to a linear error caused by the combination of an angular error and a dimensional offset between the sample and the measuring system.  It is important to understand that the information the encoder is providing is only the position of the Encoder on the scale.  To illustrate this, see the figure, which shows a linear measuring device. (The apparent distortion in the measuring device is intentional - for this example - to show the measuring device with a curvature in its mounting.)

Suppose the curvature in the figure is sufficient to produce an angle of 40 arc-seconds.  If the measuring device moves 10 inches, the probe will be found to have moved 10.0039 inches, resulting in an error of +0.0039 inches.  Abbe error could be lessened by moving the measuring system closer to the sample.  This effectively solves one half of the Abbe error problem (offset) and leaves only the angular mounting problem to be solved.  Angular error can best be countered through proper design and placement of the linear scale.  Sources of angular error include:

1.    Mounting the linear scale to an imperfectly flat surface.
2.
    Mounting the linear scale to an imperfectly straight surface.
3.
    Curvature of ways (or linear bearings) used to measure the sample.
4.
    Contaminants between the probe and item being measured.
5.
    Friction in any part(s) of the measuring device.

 

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