Campbell Scientific CR9000X Measurement and Control System - Manual (Page 237)

Section 7. Measurement Instructions
7-13
7.3.4 Full Bridges
BrFull (Dest, Reps, Range, ASlot, DiffChan, ExSlot, ExChan, MesPEx,
ExmV, RevEx, RevDiff, SettlingTime, Integ, Mult, Offset)
X = result w/mult = 1, offset = 0
(Ratio-metric measurement)
⎟⎟
⎠
⎞
+
−
⎜⎜
⎝
⎛
+
= =
2 1
2
4 3
3 1 1000 1000
R R
R
R R
R
V
V
X
X
Equations below are based on
X.
( )
A
A R
R
−
=
1
2
1
A
A R
R
−
=
1
1
2
B
BR
R
−
=
1
4
3
( )
B
B R
R
−
=
1
3
4
This Instruction applies an excitation voltage to a full bridge and makes a
differential voltage measurement of the bridge output. The resulting value
(multiplier = 1, offset = 0) is the measured voltage in millivolts divided by the
excitation voltage in volts (i.e., millivolts per volt).
See Section 3.1.5 Bridge Resistance Measurements.
BrFull6W (Dest, Reps, Range1, Range2, ASlot, DiffChan, ExSlot, ExChan,
MesPEx, ExmV, RevEx, RevDiff, SettlingTime, Integ, Mult, Offset)
X = result w/mult = 1, offset = 0
(Ratio-metric measurement)
X
V
V
R
R R
R
R R
= =
+
⎛
⎝
⎜ −
+
⎞
⎠
⎟ 1000 1000
2
1
3
3 4
2
1 2
Equations below are based on X
( )
A
A R
R
−
=
1
2
1
A
A R
R
−
=
1
1
2
B
BR
R
−
=
1
4
3
( )
B
B R
R
−
=
1
3
4
This Instruction applies an excitation voltage and makes two differential voltage
measurements. The measurements are made on sequential channels. The result is
the voltage measured on the second channel (V2) divided by the voltage measured
on the first (V1). The result is 1000 times V2 / V1 or millivolts output per volt of
excitation. The connections are made so that V1 is the measurement of the voltage
drop across the full bridge, and V2 is the measurement of the bridge output.