21
8.2.1
Technical Specifications and Special Instructions for explosive gas detectors
8.2.1.1
Transfer curves for OLCT 20 detectors
The following curve shows transmitter output current values as a function of gas
concentration. Where the user connects the transmitter to a device other than a device manufactured
by OLDHAM, he must check that the transfer curve is fully compatible with its input characteristics
to ensure that the information generated by the transmitter is correctly interpreted. Equally, the
device must supply a suitable power supply voltage, allowing for cable voltage losses.
Please note:
Detectors can generate ambiguous measurements at high gas concentrations, i.e. the
current output for a > 20% concentration of gas by volume is the same as for a concentration of < 5%
by volume (bell curve). It is therefore essential that the measuring device memorises the fact that the
value has exceeded the scale and that resetting is manual rather than automatic, and follows the safety
regulations specific to the site.
0 %
100 % 120%
20
.
0 mA
4
.
0 mA
1 mA
Concentration
in % LEL
Output Current in
mA
Fault
23
.
2 mA
Fault
Содержание OLC 20
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