4 Channel Input Buffer Board Product Manual

SDAIBB3599 Manual A-1
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
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
−+
+ ININ
. 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
−+
−
ININ
.
Gain
()
G
:
The amount by which the input is multiplied before it is output.
−+
−
=
ININ
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≤−
−+
ININ
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.