Model 755R

Instruction Manual

748213-S April 2002

will cause the dumbbell and mirror to be positioned correctly in the test body.

As the charge on C1 increases, the cathode of CR2 becomes more positive. When it exceeds that on the anode, CR2 ceases to conduct and isolates the +15 VDC and -15 VDC power supply from the input circuit.

The front panel zero potentiometer R13 and detector coarse zero potentiometer add or subtract current to the input of U2 to offset any currents that may occur because of any

imbalance in the detector and the photocells BT1 and BT2.

The output current that U2 must provide to restore the dumbbell is a measure of the displacing force and thus is a function of both (a) the % oxygen concentration of the sample and (b) the sample pressure.

The output from the U1 and U2 loop is further amplified by U4 to provide a 0 to 10 VDC output that constitutes signal V.

 

 

 

 

 

 

 

 

 

 

R23

 

 

 

 

 

 

 

 

TP8

TP20

R21

150K

TP10

 

DETECTOR

 

CONTROL

 

 

 

 

 

 

 

 

 

 

 

 

 

49.9K

-

 

 

HOUSING

 

BOARD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E21 E22

 

R22

+U4

SIG. Vx 0 -+ 10V

 

 

 

 

 

 

 

R20

 

49.9K

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20K

 

 

+15V

 

 

 

 

 

 

 

 

 

 

R12

 

 

 

 

R1

 

 

 

 

 

 

FRONT

 

 

 

 

 

 

 

 

200K

R13

 

 

 

10

 

 

 

 

 

 

20K

PANEL

 

 

 

+15V

 

 

 

 

 

 

 

ZERO

 

 

 

R2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-15V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

249K

 

 

C4

 

 

R10

+15V

 

 

 

 

 

 

 

 

 

DETECTOR

 

R1

 

-15V

 

 

.01uF

 

 

3.01K

R9

 

1K

 

 

 

 

 

 

 

20K COARSE

 

 

C1

 

 

 

 

 

 

 

 

R2

 

 

 

 

 

C8

 

ZERO

 

- U2

3.3uF

CR2

 

 

 

 

 

 

 

 

 

 

-15V

 

BT1

1K

TP6

 

 

 

R7

 

 

 

 

 

 

 

.0022uF

 

 

 

+

 

R3

 

 

-U1

1.77K

 

 

 

 

 

 

 

 

 

-

 

 

 

 

 

110

 

 

 

 

 

 

BT2

R3

 

TP7

 

 

+

C7

 

+U2

 

 

 

1K

 

C3

R4

R5

.47uF

 

 

 

 

 

-

R2

C2

2M

 

 

 

 

 

 

1000pf

.47uF 1.13K

 

 

 

 

 

 

 

1K

 

 

 

 

 

 

 

+U1

 

 

R6

 

 

 

 

 

 

 

DS1

 

 

 

118K

 

 

R8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.77K

 

 

 

CURRENT

 

 

 

 

 

 

 

 

 

 

 

FEEDBACK

 

 

 

 

 

 

 

 

 

 

 

LOOP

 

 

 

 

 

 

 

 

 

 

 

Figure 5-6. Detector with First Stage Amplifier

Rosemount Analytical Inc. A Division of Emerson Process Management

Circuit Analysis

5-9