Terminal Straight Line (TSL)

Terminal Straight Line (TSL) is a straight line drawn between the measurement output at zero and at full scale.

The TSL is used as a reference for stating the accuracy of a measurement device in a more practical way to help the user determine the reading accuracy. In most applications the device will be calibrated at zero and full scale.

Since the errors may be weighted to one side of the TSL, it is possible to improve on the accuracy by using the BSL as a reference, but calibration is not as straightforward as the TSL method.
Terminal Based Linearity (TBL) or end point linearity is determined by drawing a straight line that coincides with the calibration curve at the full span point and at the zero point (IEC 61298-2, p.13). One of the major benefits of TBL is that it includes zero offset error and span setting error. This is because Terminal Based Linearity is fixed to the sensor’s full span point and zero point.

Terminal Based Linearity (TBL) or end point linearity is a method of defining linearity. It is determined by drawing a straight line (L1) between the end data points on the output curve. The data point is chosen to achieve the maximum length of the perpendicular line. The maximum deviation of any data point on a transducer output curve from a straight line drawn between the end data points on that output curve. TBL is approximately twice the magnitude of Best-Fit Straight Line (BFSL).

A benefit of sensors tested this way is that they can be easily interchanged with other units in the field because their accuracy comes from the factory and includes errors associated with setting the zero and span points.