Axetris LGD F200P2, Operation And Integration Instructions

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Axetris AG LGD F200P2 Operating Instructions - Rev D 19.09.2018 24/60
Span Offset C C
meas new
  
) (
.
 
m b x y or
  
) (
In practice, the correction values are entered: e.g. if the measured offset is -1 ppm, 1 has to be entered
under Customer offset, and if the slope for the span (or “gain”) is too steep by 5%, enter 0.95 under
Customer Span to correct the slope. Upon Save to Sensor, the correction values will be saved in the
firmware of the sensor and are also used to correct the analog output.
It is best to proceed step-wise: first, correct the offset value at zero concentration and then correct for
span at the application concentration (e.g. 50 ppm).
To go back to the standard calibration, the following values need to be entered: Offset = 0
Span = 1

Please note that if you have a two gas system like NH3 or HCl, you also can correct offset
and span for the 2
nd
gas (usually water) concentration. But here the correction is done with
the physical unit ppm. If you want to correct the offset by 5% abs. humidity, you have to
enter 50,000 ppm for offset.
2.12.5.2 Analog output adjustment
The analog output of the sensor follows the measured and transmitted concentration. To define the analog
output it is important to keep in mind that the system internally operates with an analog range between
0...1. Then the electronics drive this range to either 0…5 V or 4…20 mA.
The first part of the calculation is to normalize
your desired output values by your physical unit.
Let U
1
or I
1
be the voltage or current you want to
get at the concentration. Let C
1
and U
2
or I
2
the
voltage or current at the concentration or C
2
.
Then N
1
is the analog output value of U
1
or I
1
,
normalized by its physical unit and N
2
is the
normalized value of U
2
or I
2
. C
min
is the lower
value of the pair C
1
and C
2
and C
max
is the
higher one.
Figure 20 Preliminary considerations to define the
analog output
System with 0…5V:
 
V Offset Span C U
meas out
5
.
   
V
U
N
5
1
1

V
U
N
5
2
2

System with 4…20 mA:
 
mA mA Offset Span C I
meas out
4 16
.
    
mA
mA I
N
16
4
1
1


mA
mA I
N
16
4
2
2


2 1
2 1
C C
N N
Span



1 min
N Span C Offset
   
The span can either be positive (a rising concentration leads to a rising voltage or current) or negative (a
rising concentration leads to a falling voltage or current). Now you can transmit the calculated parameters
to the sensor.

AnalogOut_Min_Value:

AnalogOut_Max_Value:

AnalogOut_ Offset:

AnalogOut_ Span:
C
min
C
max
Offset
Span
You will find additional examples in the appendix of this manual in Annex C.

If you correct offset and span in the customer calibration, like described in Ch. 2.7, it is
directly linked to the analog output. Please adapt the customer calibration first, so that the
measured concentration fits to your set points. And then adjust the analog output of
your system.