Instruction manual
AMPDIO DRIVERS
Page 241
Common Mode Voltage: In a differential measurement system, the common mode voltage usually represents an
interfering signal. The common mode voltage is the average of the voltages on the two input signal lines with
respect to ground level of the measuring system.
Comparator: An electronic circuit used to compare two values and set an indicator that identifies which value is
greater.
Compiler: High level language used to pre-process a program in order to convert it to a form that a processor can
execute directly.
Contact Closure: The closing of a switch, often controlled by an electromagnetic or solid state relay.
Conversion Time: The time required, in an analog/digital input/output system, from the instant that a channel is
interrogated (such as with a read instruction) to the moment that accurate an accurate representation of the data is
available. This could include switching time, settling time, acquisition time , converter processing time etc.
Counter: In software, a memory location used by a program for the purpose of counting certain occurrences. In
hardware, a circuit that can count pulses.
Counter/Timer Device: Converts time-dependent digital signals to a form that can be further processed by the host
PC. Typical functions include pulse counting, frequency and pulse width measurement. This can relate to time,
number of events, speed etc.
Crosstalk: A phenomenon in which a signal in one or more channels interferes with a signal or signals in other
channels.
Current Loop: (a) Data communications method using presence or absence of current to signal logic ones
and zeros.
(b) A method of analog signal transmission where the measured value is represented by a current.
The common current loop signal is in the range 4 to 20 mA, but other standards include 1 to 5 mA
or 10 to 50 mA.
DAC (D/A): Digital to Analog Converter. q.v.
Data Acquisition or Data Collection: Gathering information from sources such as sensors and transducers in an
accurate, timely and organised manner.
Debouncing: Either a hardware circuit or software delay to prevent false inputs from a bouncing relay or switch
contact.
Decibel (dB): A logarithmic representation of the ratio between two signal levels.
Digital-Analog Multiplier: Same as Multiplying DAC. q.v.
Digital Signal: A discrete or discontinuous signal; one whose various states are identified with discrete levels or
values.
Digital to Analog Converter: A device for converting a parallel digital word to an analog voltage, where the
magnitude of the output signal represents the value of the digital input.
DIP Switch: A set of switches contained in a dual in line package.
Drift: Small variations in a measured parameter over a period of time.
Drivers: Part of the software that is used to control a specific hardware device.
Expansion Slots: The spaces provided in a computer for expansion boards that enhance the basic operations of
the computer.
FIFO: First In First Out. A buffer memory that outputs data in the same order that they are input.
Form A, Form B, Form C Contacts: Relay contact sets which are normally open, normally closed and changeover
respectively.
Four Quadrant Operation: In a multiplying DAC, four quadrant operation means that both the reference signal and
the number represented by the digital input may both be either positive or negative polarity. The output obeys the
rules of multiplication for algebraic sign.
GAL (Generic Array Logic): Programmable logic device where the architecture and functionality of each output is
defined by the system designer.
Handshaking: Exchange of predetermined codes and signals between two data devices to establish and control a
connection.
Hardware: The visible parts of a computer system such as the circuit boards, chassis, peripherals, cables etc. It
does not include data or computer programs.
Hexadecimal (Hex): A numbering system to the base 16.
Input/Output (I/O): The process of transferring data from or to a computer system including communication
channels, operator interface devices or data acquisition and control channels.
Interface: A shared boundary defined by common physical interconnection characteristics, signal characteristics
and meanings of interchanged signals.
Interrupt: A computer signal indicating that the CPU should suspend its current task to service a designated
activity.