B&B Electronics 4 Channel Input Buffer Board SDAIBB - Manual (Page 19)

SDAIBB3599 Manual A-1
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
Appendix A: Glossary
Common Mode Voltage
( )
CM
V : The voltage about which a differential
voltage swings. When this is measured on the SDAIBB it is calculated
with all voltage readings taken in reference to GND of the SDAIBB as
( )
2
− +
+
IN IN
. Note that when one of the inputs is connected to GND of
the SDAIBB the common mode voltage changes as the differential voltage
changes.
Differential Voltage
( )
DIFF
V : The difference in voltage across two points
such as the two leads on a thermocouple. When this is measured on the
SDAIBB it is calculated with all voltage readings taken in reference to
GND of the SDAIBB as
− +
−
IN IN .
Gain
( )
G : The amount by which the input is multiplied before it is output.
− +
−
=
IN IN
V
Gain out
Impedance Mismatch: When the output impedance of sensor is different
enough from the input impedance of the data acquisition device to cause
improper sensor readings.
Negative Input Differential: When the voltage and IN- is higher than the
voltage at IN-.
0
≤ −
− +
IN IN
Negative Rail: The lowest possible voltage that can be output. For the
SDAIBB there is a negative rail internal to the buffer and a negative rail on
the output of the buffer.
Positive Rail: The highest possible voltage that can be output. For the
SDAIBB there is a positive rail internal to the buffer and a positive rail on
the output of the buffer.