4-20ma Input Calibration

Note: These features can only be accessed by Client Admin users. Your Wildeye devices may be managed by a third party as a service.

Accessing

The Input Calibration page can be accessed from the Input Settings page by clicking on the calibration link in any Input row.

Data recorded from a 4-20mA analogue input

Data recorded from a 4-20mA analogue input can be calibrated using a linear or piecewise calibration by entering the relevant calibration data for the input.

Stabilization Time

Whenever the Wildeye device logs a value from a 4-20mA Input, the 12 Volt switched power output is activated to power the sensor. The stabilization time parameter is a time period to keep the power switched on before reading the sensor. Different sensors require different time periods to settle their power draw before providing an accurate reading. Take note of whether the stabilization time is measured in seconds or milliseconds.

Linear

This calculation method follows the simple linear relation between calibrated measurement value and input measurement value.

Data required:

A 0mA or 4mA low point and its corresponding value
A 20mA high point and its corresponding value
Stabilization time - time required by sensor attached to input to power up before it can provide an accurate measurement
Unit of Measure. All Inputs require a Unit of Measure.

The linear calculation is stored according to the generic linear function:

f(x) = mx + c

where m and c are constants.

The input is therefore calculated where:

f(x) = calibrated measurement value
x = input measurement value
m = reciprocal of difference between raw values
c = difference of calibrated values

Piecewise

This calculation method is defined by multiple sub functions where each sub function is applied to certain defined intervals of the main function's domain.

The piecewise calculation is stored according to piecewise functions. For example:

where specified calibrated values have to be defined within the sub functions.

Piecewise calculations are entered as per below syntax:

<raw value 1>,<calibrated value 1>;<raw value 2>,<calibrated value 2>,...