Consilium ST650EX - Sensitivity Calibration (SPAN Calibration)

ST650EX / ST650-CO
2
/ ST350EX
v3.16
24
4.1.2 Adjusting sensitivity detector (SPAN calibration)
The span calibration can only be carried out with the use of certified calibration gas. With an
infrared sensor the concentration of the calibration gas should be 20% or 50% of the
measurement range (depending on the DIP-switch setting).
With all sensors, except with infrared sensors, the Ampere level should be calculated first. This
current value depends on the gas concentration of the calibration gas, the measurement range
and the target gas. The measurement range and the target gas (calibration gas) are listed on the
type label.
Calculation current value
The current value is calculated using the following formula:
The current I defines the output current of the sensing head based on the gas concentration of
the calibration gas.
Calculation example using Methane (CH
4
)
 The measurement range 0-100 %LEL is based on the explosion level of the type of gas. For
methane the explosion level is 4.4 Vol.%. (4.4 Vol.% CH
4
≡ 100 %LEL CH
4
).
 The gas concentration of the calibration gas is e.g. 2.2 Vol.% Methane. This is 50% of the
maximum range. This means:
 The current value with this gas concentration is:
REMARK: Always use calibration gas that is equal to the target gas. If the calibration gas is
different from the target gas, contact Consilium.
Current I =
16mA
100%
æ
è
ç
ö
ø
÷
´ gas concentration [%LEL]
æ
è
ç
ö
ø
÷
+ 4mA
Current I =
16mA
100%
æ
è
ç
ö
ø
÷
´ 50% LEL
æ
è
ç
ö
ø
÷
+ 4mA
C
u
r
r
e
n
t
I
=
1
2
.
0
0
m
A