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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 isolatedcircuit. In reference to data acquisition, isolationusually 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).
Data Acquisition987995Glossary G-3 Start of Scan In relation to ZonicBook/618E, “start of scan” is a signal that is internal to the unit. 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.