EsiWelma TUS40-20, Instruction Manual

Page: 14 / 28

Type / No.
Rev. Date Page Total pages
EW082.695_en 5 02 August 2010
14 28
EsiWelma
s.r.l.
4.4 Calibration mode
The UR20 is calibrated by two measurement values. The first of the two values is always
zero - no gas measured, make exception O
2
that in free air has a concentration of 20,9%;
the second is the factory-calibrated set point of:
•
50% of LEL (mid scale) for explosive gases
•
500 PPM (full scale) for toxic gases
•
0,5% Vol. only for CO
2
sensor
•
4,0% Vol. Only for O
2
Except for the infrared sensors, (see NDIR_1,2) that do not handle some of the parameters,
is possible view the sensor calibration values, pressing
1
in the Setting Mode. The display
will show the following:
Where:
TTTTTTT = Abbreviation of sensor type
XXXXX = Value in steps of the A/D converter of the 1
st
calibration set point
XXXXX = Value in steps of the A/D converter of the 2
nd
calibration set point
ZZZ = Units of the concentration (PPM or LEL)
KKK = Value of concentration
SSSS = Steps of the A/D converter equivalent to the measured value
Press ESC to return to Setting mode from this display
If the gas used comes in different concentrations from 50% LEL or 500 PPM, it is possible
to change the correspondence of the LEL percentage in the 2nd calibration set point.
Press key
2
from the Setting mode and the following display will appear:
Where:
ZZZ = Unit of measure of the concentration (PPM, LEL or %)
KKK = Value of concentration of the 2nd calibration set point
Press keys
0
to
9
to set the correspondence of the LEL (or PPM) percentage in the 2nd
calibration set point.
Lastly, press ENTER to memorise the set point value
Press ESC to return to Setting mode from this display
S e n s o r : T T T T T T T
C a l . 0 = X X X X X
C a l . m a x = Y Y Y Y Y
Z Z Z = K K K A D C = S S S S
Fig. 4.8
P h a s e 2 : Z Z Z = K K K
Fig. 4.9