Campbell Manufacturing CR10 7&9, 6 or, 6 or, 6 or, 6 or, 6,8,9, Offset, Instr.#, 7 or 9 Rf, Multiplier;, Instr. Result, SECTION 13. CR10 MEASUREMENTS

SECTION 13. CR10 MEASUREMENTS

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

multiplier and stores the result in the original location. Instruction 42 computes the reciprocal of a value in an input location. Table 13.5-2 lists the instructions used to compute the resistance of any single resistor shown in the diagrams in Figure 13.5-1, provided the values of the other resistors in the bridge circuit are known.

TABLE 13.5-2. Calculating Resistance Values from Bridge Measurement

Instr. Result

4X = Vx(Rs/(Rs+Rf))

X/Vx

Rs = Rf ________

1-X/Vx

1

Rf = ____________________

((X/Vx)/(1-X/Vx))/Rs

5X = Rs/(Rs+Rf)

X

Rs = Rf _____

1-X

1

Rf = _____________

(X/(1-X))/Rs

6,8,9* X = 1000 [R3/(R3+R4)-R2/(R1+R2)]

1

R1 = _______________

(X1/(1-X1))/R2

where X1 = -X/1000 + R3/(R3+R4)

Instr.#	Multiplier;	Offset
4	1/Vx	0
59	Rf
4	1/Vx	0
59	1/Rs
42
5	1	0
59	Rf
5	1	0
59	1/Rs	0
42
*used for full bridge
6 or 9	-0.001;
8	1/Vx	R3/(R3+R4)
6,8, or 9	1/R2
59
42

R2	= R1(X2/(1-X2))	6 or 9	-0.001	R3/(R3+R4)
where X2 = X1		59	R1
R3	= R4(X3/(1-X3))	6 or 9	0.001	R2/(R1+R2)
where X3 = X/1000 + R2/(R1+R2)		59	R4
	1	6 or 9	0.001	R2/(R1+R2)
R4	= _______________		1/R3
	(X4/(1-X4))/R3	59
		42

where X4 = X3
7&9* X = Rs/Rf	* used as half bridge
Rs = RfX	7 or 9 Rf	0
13-20