IOtech DaqBoard/500, Справочник по аппаратуре

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Glossary
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).
Excitation Some transducers [e.g. strain gages, thermistors, and resistance temperature detectors
(RTDs)] require a known 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 so that signals from another circuit or device do not
affect the isolated circuit.
In reference to Daq devices, 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 A series of measurements across a pre-selected sequence of 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).
Trigger An event to start a scan or mark an instant during an acquisition. The event can be defined in
various ways; e.g., a TTL signal, a specified voltage level in a monitored channel, a button
manually or mechanically engaged, a software command, etc. Some applications may use
pre- and post-triggers to gather data around an instant or based on signal counts.
TTL Transistor-Transistor Logic (TTL) is a circuit in which a multiple-emitter transistor has replaced
the multiple diode cluster (of the diode-transistor logic circuit); typically used to communicate
logic signals at 5 V.
Unipolar A range of analog signals that is always zero or positive (e.g., 0 to 10 V). Evaluating a signal in
the right range (unipolar or bipolar) allows greater resolution by using the full-range of the
corresponding digital value. See bipolar.