Industrial Scientific Oldham MX52, Commissioning, Operating And Maintenance Manual

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NOTE
For this category of explosive gas detectors, the unit’s display panel indicates 100 DIVISIONS for
100 LEL of an explosive gas.
Example:
If the reference gas is a 2.5% methane concentration, i.e. 50% LEL of methane, adjust to obtain a
display of 50 DIVISIONS.
Formula:
Maximum scale
100 DIV x n% LEL of standard gas
Numbe r of divisions to be set =
100% LEL
Maximum LEL
- Stop the injection of the standard gas, wait for the measurement to return to zero (on the
MX52 display panel). Then, press the "CALIBRATION" key (item C, Fig 27). The
flashing yellow LED is extinguished and the "C" on the display panel disappears. The
measuring channel now operates normally an calibration has been completed.
Case 2
Measuring channel connected to a detector with no integrated electronics and supplying a
standardized 4-20 mA current. (CTX50, CTX100, CTX200, CTX870, etc.).
•
Prepare the detector for calibration:
- See the remarks for zero adjustment in pure air and natural diffusion as in case 1.
- These types of detector (4-20 mA) often have a “C ALIBRATION” position (CTX870,
CTX100, etc.) or a calibration menu (CTX2042, COX2040, etc.).
This position has the effect of transmitting a 2 mA current from the detector to the
measuring unit.
- This prevents the triggering of alarms (and slaving controls) during calibrating
operations.