Definitions & Glossary Terms
The accuracy of the sensor is the maximum difference that will exist between the actual value (which must be measured by a primary or good secondary standard) and the indicated value at the output of the sensor. The accuracy can be expressed as a percentage of full scale or in absolute terms.
Analog to digital conversion (ADC)
Analog-to-digital conversion is an electronic process in which a continuously variable (analog) signal is changed, without altering its essential content, into a multi-level (digital) signal.
A characteristic of materials, sensors and sometimes instruments to make their behavior dependent on the immediate history to which they have been subjected. Typically the final settling point is different when approached from above to when it is approached from below.
Sensors do not demonstrate a perfectly linear relationship between input and ouput. This non-linearity is the maximum deviation of output from the “best fit line”, the straight line defined by sensitivity, expressed in percentage of Full-Scale Output (FSO).
Number of readings per second (speed)
Sensor measurement is often important in many test situations. When specified, measurement speed is usually stated as a specific number of readings per second for given sensor operating conditions. Certain factors such as integration period and the amount of filtering may affect overall sensor measurement speed. However, changing these operating modes may also alter resolution and accuracy, so there is often a tradeoff between sensor speed and accuracy.
Repeatability is the sensor’s ability to give the same output or reading under repeated identical conditions.
The smallest change in load that can be measured. This is usually much smaller than accuracy.
Response time (time lag)
Sensors do not change output state immediately when an input parameter change occurs. Rather, it will change to the new state over a period of time, called the response time. The response time can be defined as the time required for a sensor output to change from its previous state to a final settled value within a tolerance band of the correct new value.
Sample rate, or sampling frequency defines the number of samples per unit of time (usually seconds) taken from a continuous signal to make a discrete signal. For time-domain signals, the unit for sampling rate is in Hertz (inverse seconds, 1/s, s−1), sometimes noted as Sa/s (samples per second). The inverse of the sampling frequency is the sampling period or sampling interval, which is the time between samples.
A Secure Digital (SD) card is a tiny memory card used to make storage portable among various devices, such as car navigation systems, cellular phones, eBooks, PDAs, smart phones, digital cameras, music players, camcorders, and personal computers. An SD card features are high data transfer rate and low battery consumption; both are primary considerations for portable devices. It uses flash memory to provide nonvolatile storage, which means that a power source is not required to retain stored data.
Part of the reason the cards are called “Secure Digital” cards is because the cards have a copyright protection feature built in. The security feature, called “key revocation” means protected data on the card can only be read by specific devices. The cards can have both secured and unsecured areas on them for copyrighted and non-copyrighted data.
A device that measures a physical quantity and then converts it into signals that can be read by the user or by any other instrument.
A physical device that converts either one type of energy into another or a physical attribute into another for purposes of measurement or transfer of information. Transducers are often found in sensors. Transducers are parts of more complex devices and are used to convert energy from one form to another. Sensors are used to measure and to indicate levels of measurement.