Characteristics of Sensors

Characteristics of Sensors

It is the minimum step size within the range of measurement of a sensor in a wire-wound potentiometer, it will be equal to resistance of one turn of wire. In digital devices with ‗n‘bits,   resolution   is   ‗Full range/2n

Sensitivity:

 It is defined as the change in output response divided by the change in input response.

  Highly sensitive sensors show larger fluctuations in output as a result of fluctuations in input.

Linearity:

It represents the relationship between input variations and output variations.

 In a sensor with linear output, any change in input at any level within the range will produce the same change in output.

Range:

It is the difference between the smallest and the largest outputs that a sensor can provide, or the difference between the smallest and largest inputs with which it can operate properly.

Response time:

It is the time that a a certainsensor‘spercentage output of total change.

 It is also defined as the time required to observe the change in output as a result of change in input for example, ordinary mercury thermometer response time and digital thermometer response time.

Frequency response:

 The frequency response is the range i to the input remains relatively high.

 The larger the range of frequency response, the better the ability of the system to respond to varying input.

Reliability:

 It is the ratio between the number of times a system operates properly and the number of times it is tried.

 For continuous satisfactory operation, it is necessary to choose reliable sensors that last long while considering the cost as well as other requirements.

Accuracy:

It shows how close the output of the sensor is to the expected value.

For a given input, certain expected output value is related to how close the sensor‘s output value is to this value.

Repeatability:

is poor.

 Also, a specific range is desirable for operational performance as the performance of robots depends on sensors.

Repeatability is a random phenomenon and hence there is no compensation.

Interfacing:

  Direct interfacing of the sensor to the microcontroller/microprocessor is desirable while some add-on circuit may be necessary in certain special sensors.

  The type of the sensor output is equally important. An ADC is required for analogue output sensors for example, potentiometer output to microcontroller.

Size, weight and volume:

Size is a critical consideration for joint displacement sensors.

When robots are used as dynamic machines, weight of the sensor is important.

Volume or spaces also critical to micro robots and mobile robots used for surveillance.

Cost is important especially when quantity involved is large in the end application.