ASME PTC 19.22-2007 pdf download
ASME PTC 19.22-2007 pdf download.Data Acquisition Systems.
The following definitions are provided to clarify the terms used in this document: accuracy: the closeness ofagreementbetweena measured value and the true value [1]. analog signal: a nominally continuous electrical signal that varies in some direct correlation with another signal impressed on a transducer [2]. analog-to-digital (A/D) converter: a device that converts an analog signal to a digital signal that represents equiv- alent information [2]. binary word: the maximum number of bits treated as a unit and capable of being stored in one location [3]. bit: a contraction of the words “binary” and “digit” [3]. calibration: the process of comparing the response of an instrument to a reference standard over some measure- ment range. channel: a single path through a transmission media intended to carry the signal of an instrument reading. Typically, it carries the raw electrical signal of the instru- ment, or the output of a multiplexing function. checksum bit (check bit): a bit, such as a parity bit, derived from and appended to a bit string for later use in error detection and possibly error correction [2]. contact resistance: the resistance between the closed con- tacts of a relay in a multiplexer. crosstalk: the undesired signal appearing in one signal path as a result of coupling from another signal path [3]. data acquisition system: any device or collection ofdevices capable of accepting information, converting this infor- mation to corresponding digital information, applying prescribed processes to the information, and supplying the results of the processes [3]. data compression: the method of filtering data, by excep- tion or other means, and storing it only if meeting speci- fied criteria. The primary function of this method is to optimize data storage space by limiting the amount of data being stored. data reduction: the method by which raw test data being collected by the data acquisition system is summarized through simple calculations to produce more meaning- ful information. digital signal: data represented by discrete values or con- ditions [2]. 2 double precision: use of two digital words together to increase the resolution of a digital signal that could not be represented by a single digital word. drift: a change in system output over time independent of the input signal. filtering: electric, electronic, acoustic, optical, or software devices used to reject signals, vibrations, or radiations of certain frequencies while allowing others to pass [2]. full range (FR): the absolute value of the algebraic differ- ence between the minimum and maximum values for which the system is capable of measuring or generating. full scale: an instrument’s maximum reading or output for each of its ranges [4]. May have a higher numeric value than the range setting due to overrange capability. gain error(scale error): error in a signal due to nonlinearity in a device’s response. least significant bit (LSB): right most bit in a binary word whose value contributes the least to the overall value of the binary word and also represents the resolution of the digital word. multiplexer: a device that combines two or more informa- tion channels onto a common transmission medium [2]. noise: a disturbance that affects a signal and that may distort the information carried by the signal [2]. primary variables: those used in calculations of test results. They are further classified as: (a) Class 1: primary variables are those which have a relative sensitivity coefficient of 0.2 or greater (b) Class 2: primary variables are those which have a relative sensitivity coefficient of less than 0.2 [5]. random error: sometimes called precision; the true ran- dom error which characterizes a member of a set of measurements. The random error varies in a random, Gaussian-normal manner, from measurement to mea- surement [1]. range: an area between two limits within which a quan- tity is measured [6]. Instrument setting used in order to measure or supply a set of input or output values [4]. raw data: unreduced data prior to the application of any calculations. reference standard: a traceable instrument or process to which a system is compared during calibration. relative sensitivity coefficient: a nondimensionalized sensi- tivity coefficient.
