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GTD-1000Ex
Instruction Manual
6.4. SPAN Calibration
■ Check voltage of 18~31 V DC at both (+24 V) and (GND) of terminal block ‘CN5’.
■ Check whether (mA) terminal of terminal block ‘CN5’ is connected to the receiver.
■ Change DMM to current measuring mode, then connect (+) and (-) terminals or DMM to TP5 (+mA) and
TP6(-mA) of AMP PCB, respectively.
■ When span switch (SW6) is pressed for 3 sec, a message "[SP][AN]" flashes 3 times on FND1 and FND2 and
it enters span calibration mode.
■ When the standard calibration gas is injected into cell part, 12 mA output is observed. If the output is not 12 mA,
adjust the potentiometer 'VR3 (SPAN)' left and right to set 12 mA.
■ Adjust 'SPAN' potentiometer to obtain the correct current output for the standard gas to be displayed on FND1
and FND2.
■ When SPAN switch (SW6) is pressed for 4 sec after it is set to a desired output, result from span calibration is
displayed on FND1 and FND2. "[PA][SS]" means that the calibration has performed successfully. "[FA][IL]" means
that the calibration has not met the condition and failed. In this case, sensor and power must be reconfirmed
then calibration shall be performed again.
6.5. Gas Detector Calibration Method using Methane(CH4) Standard Gas
■ Combustible gas sensor used for device can measure various types of combustible gas. However, each combustible
gas has different properties including explosion range, heat generation rate, specific gravity, etc., therefore, it is
impossible to perform calibration with every standard gas.
■ Thus, this product uses methane gas as a reference and applies comparative properties of each combustible gas
analyzed as shown in the table below.
■ CH4 50% LEL calibration output calculation is as follows.
Range : 0-100#LEL
Output signal : 4-20mA
Calibration Gas: CH4 50% LEL /N2
balance Test point signal ( TP5, TP6 )
(200 - 40) ×
50%LEL (Standard Gas)
+ 40 = 120 = 12.0mA
100%LEL( Full Range)
■ When iso-Butane sensor is calibrated with 2.5% methane standard gas, calculate as shown below.
(Explosion range of iso-butane is 1.8% and methane is 5%.)
■ In sensor, it becomes: (100%LEL ÷ 80%LEL) × (2.5% ÷ 5%) × 100%LEL = 62.5%LEL
■ At this time, output from the sensor becomes: 20mA - 4mA) X 0.625 + 4mA = 14mA
Gas Type
Explosion Range (VOL%)
Relative Span LEL%(CH4)
Methane
CH4
5.0
100
Propane
C3H8
2.2
80
iso-Butane
C4H10
1.8
80
n-Pentan
C5H12
1.4
80
n-Hexane
C6H14
1.2
75
n-Heptane
C7H16
1.05
65
iso-Octane
C8H18
0.95
60
Methanol
CH3OH
6.7
130
Ethanol
C2H5OH
3.3
95
iso-Propanol
C3H7OH
2.2
80
Acetone
(CH3)2OH
2.6
85
Toluene
C6H5CH3
1.2
70
Ethyl Acetate
CH3COOC2H5
2.2
75
Hydrogen
H2
4.0
125
Ammonia
NH3
15
150
Cyclohexane
C6H12
1.3
75
Acetylene
C2H2
2.5
35
Ethylene
C2H4
2.7
95
6. Calibration and Maintenance
6. Calibration and Maintenance
[Figure 11. SPAN Calibration related Parts]
