Systech Instruments EC900 series Operator's Instruction Manual page 21

ACD If the auto-calibrate option is fitted, every x hours the calibration gas will automatically be fed
to the measuring cell and after a few minutes the analyzer will self calibrate. Acd is set in hours.
Auto calibrating on a weekly basis would mean an Acd of 168 hours. A setting of 0 turns the feature
off.
LIFE The value shown is an approximation of the operational lifetime left in the cell in percent. A
figure of 50 would mean that half of the life of the cell had been used. If the instrument was in service
for 2 years, then the cell would last for approximately another 2 years. For RACE type instruments
which utilise two measuring cells LIFEL shows the remaining life of the ppm cell and LIFEH shows
the life of the % cell.
GAS With some configurations the balance/background gas will have an effect on the calibration of
the analyzer. An instrument set up correctly to measure oxygen in nitrogen will not read correctly on
oxygen in argon. This calibration factor is due to the molecular weight of the background gas.
Setting and changing the gas factor to the correct molecular weight for the background gas will
always make the analyzer read correctly. The table below gives some common molecular weights;
other gas molecular weights can be found from reference books.
Gas mixture molecular weights can be ascertained by a direct relationship,
i.e. a gas background of 60% helium and 40% argon will be
(0.6 x 4.0) + (0.4 x 39.91) = 2.4 + 15.96 = 18.36
ANCHx The analogue outputs are software configurable and the can be set for Voltage 0-10Volts,
Current loop, 4-20mA or 0-20mA.
Set the output to the table below:
Note that each output is independent and can be set for any output type.
PASS Used to enter into Page 1 of the programme menu. Here is where all the parameters for
commissioning will be set.
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EC900 Series Operation Manual
GAS
Nitrogen
Argon
Helium
Hydrogen
Sulphur Hexafluoride
Ethane
Ethylene
Propane
Methane
DIGIT OUTPUT TYPE
0 4-20mA
1
0-20mA
2
0-10 Volts
MOLECULAR
WEIGHT
28.02
39.91
4.0
2.02
146.0
30.07
28.05
44.0
16.04
V4.7
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