4.0 Op era tion
4.1
Cali bra tion
Ac ti vat ing the Cali bra tion Switch will auto -
mati cally dis able the alarm cir cuits by fix ing
the ana log out put cur rent to 1.5mA (0mA op -
tional). When us ing a Gen eral Moni tors dis -
play mod ule, this cali bra tion cur rent will
in hibit the alarm cir cuits and pre vent send ing
gas con cen tra tion in for ma tion dur ing the cali -
bra tion pro cess.
Gen eral Moni tors rec om mends that the
Model S214 Hy dro gen Sul fide (H
2
S) Gas
Smart Sen sor be cali brated one hour af ter and
twenty four hours af ter ini tial start- up, and
that cali bra tion be checked at least every
ninety days to en sure the in teg rity of the sys -
tem.
Gen eral Moni tors is not im ply ing that the cus -
tomer should ex pect prob lems with sen sor life
or sta bil ity, but “fre quent” cali bra tion checks
merely en sure the in teg rity of the life pro tect -
ing equip ment.
The above state ment is not in tended to dis -
cour age the cus tomer from check ing cali bra -
tion more fre quently. Fre quent cali bra tion
checks are rec om mended for prob lem en vi -
ron ments (i.e. mud col lect ing on the sen sor
head, sen sors ac ci den tally be ing painted over,
etc, see Ap pen dix 5.5).
NOTE
:
A cali bra tion check con sists of ap -
ply ing a 50% of full scale con cen tra tion of
gas to the sen sor and ob serv ing the read ing
on the Model S214.
Gen eral Moni tors rec om mends that a cali bra -
tion sched ule be es tab lished and fol lowed. A
log book should also be kept show ing cali bra -
tion dates and dates of sen sor re place ment.
Cal i bra tion Pro ce dure
:
l
If it is suspected that hydrogen sulfide gas
is present, it will be necessary to purge the
sensor with clean air.
l
Place the magnet over the GMI Logo on
the cover of the unit and hold it there until
“
AC
” appears on the display (about ten
seconds).
l
Apply a concentration of H
2
S gas,
equivalent to 50% of full scale, to the
sensor. The display will change from
“
AC
” to “
CP
” indicating that the sensor is
responding to the gas.
l
After three to five minutes the display will
change from “
CP
” to “
CC
” indicating that
the calibration is complete. Remove the
calibration gas and allow the sensor to see
clean air. The display will indicate a few
parts per million and then drop to “0".
l
The unit is now calibrated and the new
values have been stored in the NOVRAM
(non-volatile memory).
11
GENERAL MONITORS
Model S214
fig ure 13
