Spectrum Controls 1746sc-NI8u - Manual (Page 7)

Preface iii
CJC - (Cold Junction Compensation) The means by which the module
compensates for the offset voltage error introduced by the temperature at
the junction between the thermocouple lead wire and the input terminal
block (the cold junction).
Common mode rejection ratio (CMRR) - The ratio of a device’s
differential voltage gain to common mode voltage gain. Expressed in dB,
CMRR is a comparative measure of a device’s ability to reject
interference caused by a voltage common to its terminal relative to
ground.
Common mode voltage – The voltage difference between the negative
terminal and analog common during normal differential operation.
Configuration word – Contains the channel configuration information
needed by the module to configure and operate each channel. Information
is written to the configuration word through the logic supplied in your
ladder program.
Cut-off frequency - The frequency at which the input signal is attenuated
3 dB by the digital filter. Frequency components of the input signal that
are below the cut-off frequency are passed with under 3 dB of attenuation
for low-pass filters.
dB (decibel) – A logarithmic measure of the ratio of two signal levels.
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.
Digital filter - A low-pass filter of the A/D converter. The digital filter
provides high-frequency noise rejection.
Effective resolution – The number of bits in the channel data word that
do not vary due to noise.
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 values.
Gain drift – The change in full-scale transition voltage measured over the
operating temperature range of the module.
Input data scaling - Depends on the data format that you select for the
channel data work. You can select from scaled-for-PID or Engineering
Units for millivolt, milliamp, thermocouple, RTD, or CJC inputs, which you
must compute to fit your application’s temperature or voltage resolution.