Measurement Computing DataShuttle - Manual (Page 125)

DataShuttle and DynaRes 11-12-01 Glossary - 3
Resolution
The smallest increment that can be detected in a quantity. Resolution is often specified in bits (12-bit, 16-
bit, etc.), but is most accurately specified in the same units as that of what is being measured, such as
microvolts when measuring a voltage, or microamperes when measuring current.
RTD
Resistance temperature detector. A sensor that changes resistance with temperature. It is usually made of
metal such as platinum or nickel.
Sensor
A device used to measure a physical parameter. In computer data acquisition, sensors convert the physical
signal into an electrical signal. A sensor may generate the signal such as how a thermocouple generates a
voltage, or the sensor may modify a signal such as how an RTD modifies the current that passes through it.
Sink Current
The current that flows into an output when it is low. Sink current flows into an open collector output when it
is on or conducting.
Software
The programs and data that are stored in memory or on a diskette in a computer. See “Hardware.”
Source Current
The current that flows out of an output when it is high. An open collector output cannot produce source
current unless it is connected with a pull-up resistor.
Thermistor
A sensor that changes resistance with temperature. It is made of a semiconducting material that has a very
large and very nonlinear change in resistance.
Thermocouple
A sensor that produces a voltage proportional to temperature. It consists of two dissimilar metals connected
to form a junction.
Transducer
A sensor. This often refers to a sensor with some signal processing or power regulation built in.
Transmitter
A device that amplifies and transmits an input signal to another device. In a current loop it is the device that
converts a sensor input into a current output.
TTL
A type of digital electrical signal. The low level is between 0 and 0.4 volts. The high level is between 2.4
and 5.0 volts.