Rockwell Automation 1769-IF16V Compact High Density Analog Input Modules - Manual (Page 76)

76 Publication 1769-UM018A-EN-P - October 2008
Glossary
data word – A 16-bit integer that represents the value of the analog
input channel. The channel data word is valid only when the channel
is enabled and there are no channel errors. When the channel is
disabled the channel data word is cleared (0).
digital filter – A low-pass filter incorporated into the A/D converter.
The digital filter provides very steep roll-off above it’s cut-off
frequency, which provides high frequency noise rejection.
filter – A device that passes a signal or range of signals and eliminates
all others.
filter frequency – (-3 dB frequency) The user-selectable frequency.
full scale – The magnitude of voltage or current over which normal
operation is permitted.
full scale error – (gain error) The difference in slope between the
actual and ideal analog transfer functions.
full scale range – (FSR) The difference between the maximum and
minimum specified analog input values.
input image – The input from the module to the controller. The input
image contains the module data words and status bits.
LSB – (Least Significant Bit) The bit that represents the smallest value
within a string of bits. For analog modules, 16-bit, two’s complement
binary codes are used in the I/O image in the card.
For analog inputs, the LSB is defined as the rightmost bit, bit 0, of the
16-bit field. For analog outputs, the three rightmost bits are not
significant, and the LSB is defined as the third bit from the right, bit 2,
of the 16-bit field.
linearity error – An analog input or output is composed of a series
of voltage or current values corresponding to digital codes. For an
ideal analog input or output, the values lie in a straight line spaced by
a voltage or current corresponding to 1 LSB. Any deviation of the
converted input or actual output from this line is the linearity error of
the input or output. The linearity is expressed in percent of full scale