9023927 - 2nd edition - May 2007
Page 17 of 72 Pages
Start-up
Analogue signal
— A current between 4 and 20 mA flows through the current loop during normal op-
eration. This current is proportional to the gas concentration.
— The Polytron 7500 uses various current values to indicate the operating status:
Display
An alarm is triggered:
Current
Meaning
4 mA
Zero point
20 mA
Full-scale value
<3.2 mA
Fault
3.8 mA ... 4 mA
Sensor drift below zero point
20 mA ... 20.5 mA
Measuring range exceeded
>21 mA
Fault in analogue output
3.4 mA
Maintenance signal
<3.2 mA
1)
for 1 second
1)
every 10 seconds1)
1)
Factory setting; can be configured as desired, page 52.
Warning signal
(factory setting: off)
— In measuring mode, the display shows the actual gas concentration, e.g.:
— when the alarm threshold for the concentration alarm is exceeded,
— if the measured concentration exceeds the full-scale value:
the special symbol »
Y
Y
Y
Y
« is then displayed instead of the measured value.
— If the measured concentration drops below the calibrated zero point:
the special symbol »
X
X
X
X
« is then displayed instead of the measured value.
0
1
82392
7_1_en.eps
NF
3
ppm
0.9
0
1
92392
7_1_en.eps
NF
3
A1
5.0
0202392
7_1_en.eps
NF
3
ppm
Y
Y
Y
Y
02
1
2392
7_1_en.eps
NF
3
ppm
X
X
X
X
