Measurement Computing LogBook Series - Manual (Page 220)

xii Glossary 887199 LogBook User’s Manual
Digital
A digital signal is one of discrete value, in contrast to a varying signal. Digital data is represented by combinations
of binary digits (0s and 1s).
Digital-to-Analog Converter (DAC)
A circuit or device that converts digital values (binary bits), into analog signals.
Differential mode
The differential mode measures a voltage between 2 signal lines for a single channel. (Also see single-ended
mode).
Differential mode voltage
Differential mode voltage refers to a voltage difference between two signals that are referenced to a common point.
Example: Signal 1 is +5 VDC referenced to common. Signal 2 is: +6 VDC referenced to common.
If the +5 VDC signal is used as the reference, the differential mode voltage is:
+1 VDC (+ 6 VDC - +5 VDC = +1VDC).
If the +6 VDC signal is used as the reference, the differential mode voltage is:
-1 VDC (+ 5 VDC - +6 VDC = -1 VDC).
DIP Switch
A group of miniature switches in a small Dual In-line Package (DIP). In systems where configuration can not be
made through software alone, DIP switch settings or jumpers are often used to configure the hardware. In many
cases a software setting that matches the hardware setting must be made. DIP switches are often used for
addressing.
ESD
Electrostatic discharge (ESD) is the transfer of an electrostatic charge between bodies having different electrostatic
potentials. This transfer occurs during direct contact of the bodies, or when induced by an electrostatic field. ESD
energy can damage an integrated circuit (IC).
Excitation
Some transducers [e.g. strain gages, thermistors, and resistance temperature detectors (RTDs)] require a known
voltage or current input in order for the sensor to operate. This known input is called the Excitation.
Gain
The degree to which a signal is amplified (or attenuated) to allow greater accuracy and resolution; can be
expressed as ×n or ±dB.
Isolation
The arrangement or operation of a circuit so that signals from another circuit or device do not affect the isolated
circuit. Isolation usually refers to a separation of the direct link between the signal source and the analog-to-digital
converter (ADC). Isolation is necessary when measuring high common-mode voltage.
Linearization
Some transducers produce a voltage in linear proportion to the condition measured. Other transducers (e.g.,
thermocouples) have a nonlinear response. To convert nonlinear signals into accurate readings requires software
to calibrate several points in the range used and then interpolate values between these points.
Multiplexer (MUX)
A device that selects a signal from among several signals and outputs it on a single channel.
Sample (reading)
The value of a signal observed on a channel at an instant in time. When triggered, the ADC reads the channel and
converts the sampled value into a digital representation.
Scan
A series of measurements across a pre-selected sequence of channels.