Cambridge Sensotec Rapidox 1100L Oxygen Analyser Instruction Manual
7.7
Analogue Outputs
The standard industrial analogue outputs (0-10V and 4-20mA) for both oxygen
and pressure are accessible via the terminal block (6) on the rear panel. Note that
the ranges of the 0-10V and 4-20mA are tied together so changing one alters the
other. In the case of oxygen, the outputs are factory set to provide a linear
response in the range 0-10,000ppm that will cover most applications. However
the lower and upper values are fully user-programmable using the keypad (2) or
the software provided (section 8). A more details description is given below:
The linear oxygen output mode setting produces an output that is scaled linearly
between 0 and 10V (or 4 and 20mA). So, for example, if the scale is set 0V =
0ppm (0%) O
2
and 10V = 10,000ppm (1%) O
2
then 5V would indicate an oxygen
reading of 5000ppm (0.5%) O
2
. The scaling of this example is shown in the
following plot, from which other intermediate values can also be read.
"Lin(ppm)"
Linear output mode
0
1.25
2.5
3.75
5
6.25
7.5
8.75
10
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
O
2
(%)
O
2
V
ol
ts
out
put
4
6
8
10
12
14
16
18
20
O
2
m
A
out
put
Figure 3: 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.
Version 1.6
10
Last printed 16/11/2011 16:59:00