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USER GUIDE
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Revised 2/1/2019
JENE-EG534-V2
Page 19 of 31
Linear
Applies to VoltageInputPoint, ResistiveInputPoint, and VoltageOutputWritable points. Typically, the point’s
output value is set to a unit of measurement other than Device Facets (voltage or resistance). The Linear selection
provides two fields to make the transition:
• Scale: Determines linear response slope.
• Offset: Offset used in output calculation.
For related details, see “Scale and offset calculation (linear)” on page 19.
Note: For a VoltageInputPoint used for a 4-to-20mA sensor (shunt resistor on UI input), another primary
conversion type should be used, if available: 500 Ohm Shunt, with Linear typically selected as the “secondary”
conversion. See more about that other conversion type above.
Reverse Polarity
Useful in a BooleanInputPoint or BooleanOutputWritable to reverse the logic of the hardware binary input or
output.
Note: Be careful in the use of the reverse polarity conversion, as it may lead to later confusion when
troubleshooting logic or communications problems.
Thermistor Type 3
Applies to a ThermistorInputPoint, where this selection provides a “built-in” input resistance-to-temperature value
response curve for Type 3 Thermistor temperature sensors.
Tabular Thermistor
Applies to a ThermistorInputPoint, where this selection provides a control for a popup dialog for a custom
resistance-to-temperature value response curve, including ability to import and export curve response files. For
more details, see “Tabular Thermistor notes” on page 26 and “Curve File Import/Export notes” on page 28.
Scale and offset calculation (linear)
Unless you want a VoltageInputPoint or VoltageOutputWritable to operate with facets (units) of volts, you must set
the point’s facets to the desired units, and set the ProxyExt Conversion property to Linear.
You must then enter your calculated scale and offset values in the Linear fields. Also, you must set the
“Units” in its Linear Calibration Ext to match an input point’s facets—otherwise a fault status occurs.
Note: This also applies to any linearly-responding ResistiveInputPoint using point facets other than ohms.
Use the following formulas to calculate the Linear scale and offset values:
Where: x1 and x2 are the values (e.g. voltage), and y1 and y2 are the corresponding desired units.
• Scale
Scale = (y2 - y1) / (x2 - x1)
• Offset
Offset = y1 - (Scale * x1)
See example 1 and example 2.
Scale and off set calculation… Example 1
You have a 6-to-9Vdc actuator to control with a VoltageOutputWritable, in terms of 0-to-100% input.
Configure this point’s facets to have units: “misc,” “percent” (%).
Set the ProxyExt’s Conversion property to Linear, and enter these calculated scale and offset values:
• Scale
Scale = (y2 - y1) / (x2 - x1)
Scale = (100% - 0%) / (9V - 6V) = 100/3 = 33.3333333
• Offset
Offset = y1 - (Scale * x1)
Offset = 0% - (33.3333333 * 6V) = 0 - 200 = -200
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