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Glossary C
Calibration: The process of adjusting an instrument or compiling a deviation chart so that its reading can be correlated to the actual value being measured.

Capacitance: Letter C. Units: Farad F,microfarad uF, nanofarad nF, picofarad pF.  It is the property that allows a component to store electric charge when a potential difference exists between its terminals.

Capacitor: An electronic component that stores electrical charge.

Cascade: A method of connecting circuits in series so that the output of one is the imput of the next.

Cathode: identified by the letter k - the banded end of a diode.

Celsius (centrigrade): A temperature scale defined by 0°C at the ice point and 100°C at boiling point of water at sea level.

Cell: A single source of voltage.

Ceramic capacitor: Generally a single layer capacitor that is flat and has a brown coating, Also have the name monoblock or monolithic in which the capacitor is made even smaller by creating multy-layers and coated in orange or blue paint.

Character: A letter, digit or other symbol that is used as the representation of data. A connected sequence of characters is called a character string.

Chip: Another name for Integrated Circuit or the piece of silicon on which semiconductors are created.

Choke: An inductor designed to present a high impedance to alternating current.

Chop Mode: A display mode of operation in oscilloscope in which small parts of each channel are traced so that more than one waveform can appear on the screen simultaneously.

Circuit Loading: The unintentional interaction of the probe and oscilloscope with the circuit being tested, distorting the signal.

Clipping: The term applied to the phenomenon which occurs when an output signal is limited in some way by the full range of an amplifier, ADC or other device. When this occurs, the signal is flattened at the peak values, the signal approaches the shape of a square wave, and high frequency components are introduced. Clipping may be hard, as is the case when the signal is strictly limited at some level; or it may be soft, in which case the clipping signal continues to follow the input at some reduced gain.

Clock: The device that generates periodic signals for synchronization.

CMR (Common-Mode Rejection): The ability of a panel meter to eliminate the effect of AC or DC noise between signal and ground. Normally expressed in dB at dc to 60 Hz. One type of CMR is specified between SIG LO and PWR GND. In differential meters, a second type of CMR is specified between SIG LO and ANA GND (METER GND).

CMV (Common-Mode Voltage): The AC or DC voltage which is tolerable between signal and ground. One type of CMV is specified between SIG LO and PWR GND. In differential meters, a second type of CMV is specified between SIG HI or LO and ANA GND (METER GND).

CMOS: Complimentary Metal-Oxide-Semiconductor, Family of logic devices that uses p-type and n-type channel devices on the same IC. It has the advantage of offering medium speed and very low power requirements.

Coax: Coaxial cable. A round cable with a central conductor and screening around with a insulating medium between.

Coherence Function: A frequency domain function computed to show the degree of a linear, noise-free relationship between a system's input and output. The value of the coherence function ranges between zero and one, where a value of zero indicates there is no causal relationship between the input and the output. A value of one indicates the existence of linear noise-free frequency response between the input and the output.

Coil: A conductor wound in a series of turns.

Collector: One terminal of a transistor.

Color Code: The ANSI established color code for thermocouple wires in the negative lead is always red. Color Code for base metal thermocouples is yellow for Type K, black for Type J, purple for Type E and blue for Type T.

Common Base Connection: Same as ground base connection. A mode of operation in which the base is common to both the imput and output circuits and is usually earthed. The emitter is used as the input terminal and the collector as the output terminal. (Grounded= grounded to AC signals).

Common Collector Connection: Grounded collector connection. Also called the emitter-follower. A mode of operation in which the collector is common to both the imput and the output circuits and is usually connected to one of the power rails.

Common Emitter Connection: Same as ground emitter connection. A mode of operation for a transistor in which the emitter is common to the imput and output circuits. The base is the imput terminal and the collector is the output terminal.

Common Mode Rejection Ratio: The ability of an instrument to reject interference from a common voltage at its input terminals with relation to ground. Usually expressed in db (decibels).

Communication: Transmission and reception of data among data processing equipment and related peripherals.

Compensated Connector: A connector made of thermocouple alloys used to connect thermocouple probes and wires.

Compensating Alloys: Alloys used to connect thermocouples to instrumentation. These alloys are selected to have similar thermal electric properties as the thermocouple alloys (however, only over a very limited temperature range).

Compensating Loop: Lead wire resistance compensation for RTD elements where an extra length of wire is run from the instrument to the RTD and back to the instrument, with no connection to the RTD.

Compensation: 1) An addition of specific materials or devices to counteract a known error. 2) A probe adjustment for 10X probes that balances the capacitance of the probe with the capacitance of the oscilloscope.

Complementary transistor: A PNP and NPN pair used in a push-pull circuit.

Complex Function: Any mathematically defined relationship given by the following expression:

             y(x) = a(x) + ib(x)
         x= the real variable
         a(x) = the real part of y(x)
         b(x) = the imaginary part of y(x)
Complex functions are usually expressed in terms of both their amplitude and phase.

Complex Wave: The resultant form of a number of sinusoidal waves that are summed together forming a periodic wave. Such waves may be analyzed in the frequency domain to readily determine their component parts.

Compiler: A program that translates a high-level language, such as Basic, into machine language.

Condenser: Obsolete term for capacitor.

Conventional current flow: During the beginning of invention of electric circuits it was thought that current flowed from positive to negative. See Electron flow for the opposite direction of flow.

Conductance: The measure of the ability of a solution to carry an electrical current. (See Equivalent Conductance)

Conduction: The conveying of electrical energy or heat through or by means of a conductor.

Confidence Level: The range (with a specified value of uncertainty, usually expressed in percent) within which the true value of a measured quantity exists.

Conformity Error: For thermocouples and RTDs, the difference between the actual reading and the temperature shown in published tables for a specific voltage input.

Continuous Spectrum: A frequency spectrum that is characterized by non-periodic data The spectrum is continuous in the frequency domain and is characterized by an infinite number of frequency components.

Control Character: A character whose occurrence in a particular context starts, modifies or stops an operation that effects the recording, processing, transmission or interpretation of data.

Counts: The number of time intervals counted by the dual-slope A/D converter and displayed as the reading of the panel meter, before addition of the decimal point.

Coupling: The method of connecting two circuits together. Circuits connected with a wire are directly coupled; circuits connected through a capacitor or a transformer are indirectly (or AC) coupled.

CPS: Cycles per second; the rate or number of periodic events in one second, expressed in Hertz (Hz).

CPU: Central processing unit. The part of the computer that contains the circuits that control and perform the execution of computer instructions.

Critical Damping: Critical damping is the smallest amount of damping at which a given system is able to respond to a step function without overshoot.

CRT(Cathode-Ray Tube): An electron-beam tube in which the beam can be focused on a luminescent screen and varied in both position and intensity to produce a visible pattern. A television picture tube is a CRT.

Current: The rate of flow of electricity. Current is measured in amps (milliamps and microamps). The unit of the ampere (A) defined as 1 ampere = 1 coulomb per second. Conventional current flows from positive to negative. Electrons flow from negative to positive - called "electron flow".

Cursor: An on-screen marker that you can align with a waveform to take accurate measurements.

Curve Fitting: Curve fitting is the process of computing the coefficients of a function to approximate the values of a given data set within that function. The approximation is called a "fit". A mathematical function, such as a least squares regression, is used to judge the accuracy of the fit.

Cut-off Frequency: The frequency at which the gain or amplification is unity.

Cycle Time: The time usually expressed in seconds for a controller to complete one on/off cycle.