IOtech DaqBoard/3000USB Series, Руководство пользователя

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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.
Range
For the purposes of calculating accuracy, range is equal to the full dynamic input voltage. For example, the
full-scale range is 20V for the -10 to +10V range.
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.