Calculating Resistance Values From Bridge Measurement - Campbell CR510 Operator's Manual

Calculating the actual resistance of a sensor
which is one of the legs of a resistive bridge
usually requires the use of one or two Processing
Instructions in addition to the bridge
measurement instruction. Instruction 59 takes a
value, X, in a specified input location and
computes the value MX/(1-X), where M is the
TABLE 13.4-2. Calculating Resistance Values from Bridge Measurement
Instr. Result
4 X = V (R /(R
x s
X/V
________
R = R
s f
1-X/V
= ____________________
R
f
((X/V
5 X = R /(R +R
s s
X
_____
R = R
s f
1-X
1
= _____________
R
f
(X/(1-X))/R
6,8,9* X = 1000 [R /(R
3 3
1
= _______________
R
1
(X /(1-X
1
where X = -X/1000 + R
1
R = R (X /(1-X
2 1 2
where X = X
2
R = R (X /(1-X
3 4 3
where X = X/1000 + R
3
1
= _______________
R
4
(X /(1-X
4
where X = X
4
7&9* X = R /R
s f
R = R X
s f
R = R /X
f s
+R ))
s f
x
x
1
)/(1-X/V ))/R
x x s
)
f
s
+R )-R /(R +R )]
4 2 1 2
))/R
1 2
/(R +R )
3 3 4
))
2
1
))
3
/(R +R )
2 1 2
))/R
4 3
3
SECTION 13. CR510 MEASUREMENTS
multiplier and stores the result in the original
location. Instruction 42 computes the reciprocal
of a value in an input location. Table 13.4-2 lists
the instructions used to compute the resistance of
any single resistor shown in the diagrams in
Figure 13.4-1, provided the values of the other
resistors in the bridge circuit are known.
Instr.#
4
59
4
59
42
5
59
5
59
42
*used for full bridge
6 or 9
8
6,8, or 9
59
42
6 or 9
59
6 or 9
59
6 or 9
59
42
* used as half bridge
7 or 9
7 or 9
42
Multiplier; Offset
1/V 0
x
R
f
1/V 0
x
1/R
s
1 0
R
f
1 0
1/R
s
-0.001;
1/V
x
R /(R +R
3 3 4
1/R
2
-0.001 R /(R +R
3 3 4
R
1
0.001 R /(R +R
2 1 2
R
4
0.001 R /(R +R
2 1 2
1/R
3
R 0
f
1/R 0
s
13-15
)
)
)
)