Measurement Computing WaveBook rev.5.3 - Manual (Page 153)

Data Acquisition 969597 Glossary G-3
Mapped Channel In relation to the WBK17, a mapped channel is one of 16 signals that can get multiplexed into a
channel’s counter module. The mapped channel can participate with the channel’s input signal
by gating the counter, clearing the counter, etc. The 16 possible choices for the mapped
channel are the 8 input signals (post debounce) and the 8 detection signals.
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 channels that are selected for sampling.
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).
Start of Scan In relation to the WBK17, “start of scan” is a signal that is internal to the WBK17. It signals the
start of a scan group and therefore pulses once every scan period. It can be used to clear the
counters and latch the counter value into the acquisition stream.
Terminal Count In relation to theWBK17, this signal is generated by the counter value. There are only two
possible values for the terminal count: 65,535 (for a 16-bit counter) and 4,294,967,295 (for a
32-bit counter.) The terminal count can be used to stop the counter from rolling over to zero.
Ticksize In relation to theWBK17, the ticksize is a fundamental unit of time and has four possible
settings: 20ns, 200ns, 2000ns, 20000ns. For measurements that require a timebase reference
like period or pulsewidth, the ticksize is the basic unit of time. The count value returned in the
scan is the number of ticks that make up the time measurement.
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.