Ideal Behavior of a Sensor/Transducer.

Ideal Behavior of a Sensor/Transducer.

Mechatronics design engineer must be knowing the capabilities and shortcomings of a transducer or measurements system to properly assess it's performance. There are a number of performance-related parameters of a transducer or measurement system. Sensor specifications inform the engineer and the user about the deviation from the ideal behaviour of the sensor.

The following terms are used to define the performance of the transducer and often measurement System as a whole. The design process begins with a need form, perhaps a customer or clients. This may be identified by market research Being used to establish the need for potential customers.

Range

The range of a transducer define the limits between which the input can vary. The span is the maximum value of the input minus the minimum value.

Error

The error is the difference between the results of the measurements and the true value of the quantity being measured. For example, if the measurements system gives a temperature reading of 45^0 C when the actual temperature is 42^0 C then the error is +3^0C.

Accuracy

Accuracy is the extent to which the value indicated by a measurements system might be wrong. It is thus the summation of all the possible error that is likely to occur as well as the accuracy to which the transducer has been calibrated.

Sensitivity

The sensitivity is the relationship indicating how much output here is per unit input. There can be the sensitivity of the transducer to temperature changes in the environment or perhaps fluctuations in the main voltage supply.

Hysteresis

The transducer can give different output from the same value of the quantity being measured according to whether that value has been reached by the continuous increasing change or a continuously decreasing change.

Stability

The stability of the transducer is its ability to give the same output when when used to measure a constant input over a period of time. The term drift is often used to describe the change in output that occurs over time. Zero drift is used for the change that occurs in output when there is zero input.

Dead band/Time

The dead band or dead space of a transducer is the range of input values for which there is no output. The dead time is the length of time from the application of an input until the output begins to respond and change.

Resolution

When the input varies continuously over the range, the output signal for some sensor may change in small steps. Example potentiometer. The resolution is the smallest change in the input values that will produce a considerable change in the output.

Non-linearity error

For many transducers, the linearity relationship between the input and output is assumed over the working range. in some transducer, however, have a truly linear relationship and thus the error occurs as a result of the assumption of linearity. This error is defined as the maximum difference from the straight line. various methods are used for the numerical expression of the non-linearity error. The difference occurs in determining the straight line relationship against which the error is specified.

Repeatability

The term repeatability of the transducer is used to describe it's ability to give the same output for repeated application of the describe the same input values. The error resulting from the same output not being given with repeated applications is usually expressed as a % of the full range output.