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G-2 959395 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 di

fferential

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 electro

static potentials. This transfer occurs duri

ng 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

TDs)] requir

e 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 si

gnals from another circui

t or device do not

affect the isolated circuit.

In reference to Daq devices, iso

lation usual

ly 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

nto accurate readin

gs 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. W

hen triggered, the ADC reads the

channel and conver

ts 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-specif

ic settings.

Simult

aneous

Sample-and-Hold

An o

peration 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 wi

th other channels. (Al

so see differential mode).

Trigger An event to start a scan or mark an instant during an acquisition. The event can be defined in

ari

ous 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

Unipolar A range of analog signals that is always zero or positive (e.g., 0 to 10 V). Evaluating a signal in

the ri

ght range (unipolar or bipolar) allows greater resolution by using the full-range of the

corresponding digital value. See bipolar.

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