Installation Guide - Position Transducers
The selection of the resistance value is solely dependent upon the requirement of your data acquisition or control
circuitry. Accuracy and resolution are independent of the actual resistance value. Firstmark Controls has standardized
on a 5K ohm value although other resistance values are available upon request. Note that price and delivery may
be affected by selecting non-standard potentiometer resistances.
Do you have additional calibration data beyond the 3-point data table provided with the position transducers?
Firstmark Controls can provide an extra-cost acceptance test data sheet (ATDS) that contains tested electrical
and mechanical data for the position transducer including cable tension, outputs, and linearity. Please contact us if
you would like more information or if you have unique calibration requirements. For more information on linearity
and calibration, visit
.
What type of output do I get with the analog-output position transducers? How is the linearity determined?
The output and linearity for these position transducers is defined per VRCI-P-100A (published by the Variable
Resistive Components Institute). This publication defines independent linearity as the maximum deviation of the
actual function characteristics from a straight reference line with its slope and position chosen to minimize the
maximum deviations. It is expressed as a percentage of the Total Applied Voltage and is measured over the
Theoretical Electrical Travel. The slope of the reference line, if limited, must be separately specified. An Index Point on
the actual output is required. Unless otherwise specified, the Index Point will be at Õ = Õt /2. See Figure 14.
Mathematically, e/E = P(Õ/Õt) + Q±C where P is unspecified slope, Q is unspecified intercept at Õ = 0 and both P and
Q are chosen to minimize C but are limited by the End Voltage requirements.
Figure 14
What methods are available for reading the electrical outputs from the digital-output position transducers?
Quadrature (digital) outputs can be read from a variety of devices including:
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digital meters
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RS-232 and USB interfaces
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PLCs
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data acquisition boards with digital inputs
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custom-made interfaces using counter and frequency components
For sources of these items, please contact us or visit
.
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