Rosemount 755, Instruction Manual

Page: 42 / 94

M
ODEL
755 O
XYGEN
A
NALYZER
3-2
748183-H Rosemount Analytical
November 1997
%RANGE switch
R2 R1
R3
R4
R5
R6
R8
R9
CR2
U6
I G O
U3
U2
1
2
3
4
I
G
O
C5
C4
C2
U4
U5
I G O
C3 CR1 C1
U1
J1
14
13
12
10
11
5
4
3
9
8
7
1
2
17
16
15
Current Output Board
Meter
ZERO potentiometer
SPAN potentiometer
R38
R33
R45
R92
R89
R90
R20
R2
R1
R67
R68
R78
R73
R64
R63
performed on the range of highest sensitivity, i.e., most narrow span. Preferably
upscale calibration should be performed on the range that will be used during sample
analysis. In some applications however, it may be desirable to perform upscale
calibration on a range of higher sensitivity, i.e., more narrow span, and then move the
% RANGE Switch to the desired operating range. For example, if the operating range
is to be 0 to 50% oxygen upscale calibration may be performed on the 0 to 25% range,
to permit use of air as the upscale standard gas.
It is necessary to calibrate the instrument at the same pressure that will be used during
subsequent operation and to maintain this pressure during operation.
The preferred calibration method uses both a downscale and an upscale standard gas,
as described in Section 3.2.1. An alternative method using an upscale standard gas
only is described in Section 3.2.2.
F
IGURE
3-1. C
ONTROL
B
OARD
- A
DJUSTMENT
L
OCATIONS