D11-044-1: Rapidox 1100ZR-H-OL-LC O
2
Analyser Instruction Manual
D11-044-1
11
Last printed 08/11/2016 12:10:00
Figure 4: Graph showing the linear output mode option for oxygen
The following general formulae can be used to calculate the oxygen from the
voltage or current outputs when set to the linear output mode:
Output type Formula for calculating oxygen from analogue output signal
0-10V
O
2
= V
out
/ 10 * (O
2H
- O
2L
) + O
2L
4-20mA
O
2
= (mA
out
– 4) / 16 * (O
2H
- O
2L
) + O
2L
Where:
O
2L
= user setting of oxygen for 0V or 4mA output
1
O
2H
= user setting of oxygen for 10V or 20mA output
1
V
out
= the measured voltage output in volts
mA
out
= the measured current output in mA
1
O
2
, O
2L
and O
2H
must all be in the same units.
2.
LOG (ppm):
This setting produces an output that is scaled logarithmically
between 0V and 10V (or 4 and 20mA). So, for example, if the scale is set to 0V
= 0.0001% (1 ppm) and 10V = 100% (1000000 ppm) then 5V would indicate
an oxygen reading of 0.1% (1000 ppm). This scale is more suitable for large
ranges of oxygen down to very low ppm levels. Note that because the scaling
is logarithmic 0V cannot be set to 0% oxygen since log(0) is -
∞
! The lowest
permitted setting is 0V = 10
-20
ppm (or 10
-24
%) O
2
. The scaling of this example
is shown in the blue line in following plot, from which other intermediate
values can also be read. For comparison, the red line shows the limitations of
using the linear oxygen output mode over the same range.
"Lin(ppm)"
Linear output mode
0
1.25
2.5
3.75
5
6.25
7.5
8.75
10
0
10
20
30
40
50
60
70
80
90
100
O
2
(%)
O
2
V
o
lt
s
o
u
tp
u
t
4
6
8
10
12
14
16
18
20
O
2
m
A
o
u
tp
u
t