Geca ST441M Manuel D'utilisation page 6

ST441 (15.05.2019)
Catalytic sensors cannot work in oxygen deficiency. It is possible to use either the disposable cylinders with
adjust valve or the high pressure ones with reduction gear. It is also necessary to use the calibration kit GECA
model TC011 (for non-corrosive gases).
"INSTRUMENT OPERATION CHECK" (Check Code: F2, F2, F1, F1): this function allows to effect a functional test
of the equipment. After having put the system in safety and inserted the "Code Test":
STATUS of OPERATION CHECK
After entering the Check Code
Starting Operation Check
Within 2 sec. the mA output
Within 2 sec. the output in mA
End Check and return to normal operation OFF
The check lasts a total time of about 16 seconds, then the detector will return to normal operating conditions.
It is advisable to perform this operation every 6-12 months according to the use.
Note: The operation can not be performed if the output is greater than 12mA (10% LEL).
"ZERO ADJUST" (Zero Code: F2, F1, F1, F2): even if there is an automatic zero adjustment system (zero tracker)
this operation must be performed only if the output is different from 4mA (0% LIE on the control unit) after the
installation and every 6-12 months based on the environmental conditions. This function must be done in clean air
only (environment without the presence of gas or other pollutants). Immediately after having inserted the "Zero Code", as a con-
firmation of the operation carried out there will be 1 flash of the Green Led and the output will become 4,0mA.
Note: The operation can not be performed if the output is greater than 12mA (10% LEL). In this case, it will be
necessary to recalibrate the unit and/or replacing the detector.
"CALIBRATION CHECK" (Cal Check Code: F2, F1, F2, F1): this operation allow to effect a real functional test of
the equipment with gas after the "Calibration" routine, or after the installation. The "Calibration Check" routine should
be done during the periodic maintenances because this is the only method to verify the instrument real functioning.
WARNING: the Cal Check Code allows to use the same cylinder 0.88% v/v Methane + Air for all types even
if they have different gas response. E.g. the ST441G. Instead, if a cylinder with 0.28% v/v Butane + Air mixture
is used for the verification, the code must not be used.
1) With the keys perform the "Cal Check Code ". Wait until the Yellow Led starts to flash (the green one remain fix)
2) Insert the TC011 over the sensor holder. Adjust the sample gas bottle valve (0.88%v/v methane in air), as the flow
meter indicates around 0.3 l/mins
3) Verify with a voltmeter connected to the Test-Point, the value reaches a value between 184 and 216mV, [cor-
responding to 20mA (±1.6) output and the control unit should be display about 20% LEL (±2)]. If the value re-
sult is more different, it is necessary to recalibrate the sensor (see "Calibration").
4) Then, close the gas bottle, remove TC011. To return to normal operation, press and hold F2, until the yel-
low LED is off and the mA output will slowly decrease up to 4mA.
WARNING: For safety, five minutes after insertion of the code, the detector returns to normal operation.
Remember that during the verification of the Central Unit will activate alarm devices.
"FULL CALIBRATION" (Calibration Code: F2, F2, F2, F1, F2, F1): this function allows completely recalibrate the
sensor and must be performed when the "CALIBRATION CHECK" has not been exceeded.
Important note: During Calibration routine the mA output indicates 0mA.
WARNING: "Full Calibration" should be performed only in clean air (environment without presence of flammable
gases or other pollutants) and using only the 20% LIE (0.88% v/v) Methane Gas mixture in air (20.9 About% O
1) With the keys perform the "Calibration Code". The Green LED starts to flash.
2) wait for the Yellow LED to light on.
3) Insert the TC011 on the sensor holder (hold it down) and adjust the sample gas bottle valve (0.88%v/v methane
in air), as the flow meter indicates around 0.3 l/mins
4) Wait around 3 minutes, then when the Green Led switch on (and while it's SWITCHED ON), press the key F2 on the
instrument and hold it pressed until the two LEDs are switched off. (WARNING: if Green continuous flashing
over 5/6 minutes calibration has failed. In this case, turn the detector off and on, after preheating, repeat the
"Calibration" procedure. Verify that the problem does not depend on the gas or the unstable flow. If the condi-
tion persists, it will be necessary to replace the detector and/or send it to the supplier for repair.).
5) Then, close the gas cylinder and remove TC011. At this point we can have two possibilities:
Yellow and Green LEDs off: the calibration routine has correctly been performed. Wait 8 seconds, until the in-
strument automatically switches off and restarts in normal operation (see chapter "Operational Description > Preheating).
Yellow LED illuminates: the routine has failed. In this case, wait 8 seconds, until the instrument automatically re-
peat Preheating, then repeat the "Calibration" routine without inserting again the code. If condition still persists, it will be
necessary to replace the detector and/or send it to the supplier for repair.
GECA S.r.l. - Via E. Fermi, 98 25064 Gussago (Brescia) Italy
Istruzione / User's Manual / Manuel d'utilisation
YELLOW LED GREEN LED mA OUTPUT (S)
OFF OFF
ON ON
OFF ON
ON ON
ON
(see Fig.3).
0 mA
0 mA for 2 seconds
increases to 4 mA for 5 seconds
increases to 20 mA for 5 seconds ALARM
gas measurement
(see Fig.3).
Tel. +39 030 3730218 - Fax +39 030 3730228
Pag. 6 / 10
Control Unit
FAULT
FAULT
NORM
NORM
).
2