Measurement Computing ZonicBook 618E rev.3.4 - Manual (Page 120)

G-2 Glossary 987995 Data Acquisition
Differential mode A 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 = +1 VDC).
If the +6 VDC signal is used as the reference, the differential mode voltage is -1 VDC
(+ 5 VDC - +6 VDC = -1 VDC).
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);
thus safe handling is required.
Excitation A voltage or current supplied to a transducer. Some transducers [e.g. strain gages, thermistors,
and resistance temperature detectors (RTDs)] require a specific voltage or current. Typically,
the variation of this signal through the transducer corresponds to the condition measured.
Gain The degree to which an input 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, such that signals from another circuit or device do not
affect the isolated circuit.
In reference to data acquisition, 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 collects signals from several inputs and outputs them on a single channel.
Sample (reading) The value of a signal on a channel at an instant in time. When triggered, the ADC reads the
channel and converts the sampled value into a 12- or 16-bit value.
Scan The term “scan” typically refers to an acquisition that consists of one sample for each configured
channel (see scan list). Note that all samples in a scan are acquired using the same clock
stimuli.
Scan List A list of channels that have been selected for sampling. A list of enabled (active) channels.
Sequencer A programmable device that manages channels and channel-specific settings.
Simultaneous
Sample-and-Hold
An operation that gathers samples from multiple channels at the same instant and holds these
values until all are sequentially converted to digital values.
Single-ended mode The single-ended mode measures a voltage between a signal line and a common reference that
may be shared with other channels. (Also see differential mode).