Overview

All sensors output a voltage that represents a particular measurement; for example a linear potentiometer has a measurement range of 0-100mm and over this range its output is 0-5 volts. The logger cannot store these voltages directly, so it converts them into digital information, a process know as analog to digital conversion (ADC). The logger looks at the voltage from the sensor at regular intervals, known as the logging rate, and converts the voltage into a binary number or counts.

When data is downloaded from the logger it creates a file known as a dataset. The dataset contains all of the samples for every channel that was logged. To be of any use the data from the sensors should be in recognized units; for example, inches, deg C or psi. This is where a channel calibration is required.

Calibrations

A calibration is a mathematical description that can be applied to a sensors data to convert it into engineering units. When you calibrate a sensor you define a set of points by specifying the x and y coordinates. A minimum of two points are required to create a calibration curve. Ideally the calibration should include points close to the maximum and minimum raw values.

The x coordinate is the binary representation of the sensor output voltage and is fixed by the resolution of the ADC. 12 bit systems have a maximum of 4096 counts. The y coordinate is the measurement of the sensor in engineering units at each of the corresponding x coordinates. The calibration tools of Power to Win let you:

enter a known calibration curve for an analog sensor
apply gain and offset calibration functions, and
choose mathematical equations that describe the behaviour of the sensor

When you choose to graph a channel using the Analysis program the calibration is attached to the raw sensor data and converts it to engineering units. Calibration information is also stored in the logger so that channel data appears in engineering units on the dash display and is also used by the onboard math engine that uses floating point engineering units for its calculations.

Calibration Types

Power to Win supports five calibration types that can be fitted to your points to define the response of the sensor over the entire measurement range. The calibration types supported are:

Interpolation
Linear
Quadratic
Table with Hold
Scale & Offset

Channel Types

Each channel is defined by a set of parameters that the logger uses to allocate memory space in the logging table. A hardware index is used to refer to the physical connection between each sensor and the logger. Each analog or digital channel connects to the logger through its main connectors or via junction boxes.

There are four types of channels defined:

physical analog sensor channels
internal system channels
digital channels, and
data stream channels

Data stream channels such as those received by a communication link to an ECU or a Tire Monitoring System (TMS) connect to the logger via a communications port. These channels do not have physical location but have a hardware index which is defined by the database generated for each manufacturers ECU.

Notes

Interpolation calibrations take longer to calculate and graph than the other defined types.
Calibrating using direct sensor readings requires USB comms to be open and online with the LCU. The Manual ADC Count must also be unchecked.

Winning Edge Electronics