Glossary Updated

October 1st, 2006

Windmill Software has updated their data acquisition glossary. They have added the following terms:

Absolute accuracy: How closely the measured value approaches the real value.

Relative accuracy: How accurately a change in signal is measured.

Analogue Input: An infinitely variable signal connected to a data acquisition system. This is generally a voltage signal. Thermocouples, strain gauge bridge circuits and gas concentration probes, for example, all produce an analogue voltage. Alternatively, the signal may be a milliamp current. In this case, the data acquisition hardware will convert the current to a voltage before accepting it.

Analogue Output: A waveform or control signal generated by the data acquisition and control equipment.

Digital Input: A digital signal going into a data acquisition device. A digital signal has only 2 states.

Digital Output: A digital signal generated by the data acquisition and control equipment. Software controls each digital output by just one bit - setting the digital line high or low.

Calibration: The process where a data acquisition device’s performance is compared to an accuracy standard, and the performance adjusted as necessary.

Current sink: The maximum current that data acquisition output channels can dissipate.

Current source: The maximum current that can be supplied by the data acquisition device for output signals.

Decibel: A logrithmic measure of the ratio between two quantities. Symbol dB.

Dynamic range: The ratio of the largest to the smallest signal that can be measured at one time. Normally expressed in Decibels (dB). The maximum signal is generally the analogue-to-digital converter’s full scale signal. The dynamic range of a DAQ device is important when both large and small signals are to be measured. Dynamic Range = 20 x log (Max Voltage / Min Voltage)

RTU: Remote Terminal Unit. A data acquisition device at a remote location which transmits data back to, and accepts commands from, a central PC (or other controller).

TCP/IP: Transmission Control Protocol/Internet Protocol. Communications protocols used to connect hosts on the Internet.

Text format: Information in the ASCII character set that is unformatted. Each byte in the file contains one character that conforms to the standard ASCII code.

The full glossary is on the Windmill website.

Entry Filed under: Data Acquisition