Oldham MX 52, Commissioning, Operating And Maintenance Manual

Page: 49 / 96

49
CAUTION
If the detector and the measuring channel are calibrated at the same time, the detector
must be left in normal operating mode but the MX52 unit must be set to calibration mode
in order to inhibit the relays.

Consult the technical manual for the detector concerned.
- Open the detector (with integrated electronics) in order to gain access to the 4 mA
adjustment and sensitivity (20 mA) potentiometers and to the terminals used to check its
4-20 mA output current.
- With these types of detector, there are two ways of checking the current supplied to the
unit:
o
by direct reading on the local display panel (internal to the detector)
o
by measurement of current on the terminals provided for that purpose (see the
manual for the detector concerned).
- Prepare the measuring channel for calibration:
- same operations as in case 1.

Adjust the detector zero.
NOTE
If the ambient air is not pure, inject air using a “synthetic air” cylinder and the gas injection pipe or
a remote calibrating fixed device with a flow rate of 60 litres per hour for 25 seconds directly on the
detector or a flow rate of 170 litres per hour for 1 min 45 s using a remote calibrating fixed device.
As soon as the signal is stable on the local display panel on the detector or with regard to the current
output (4-20 mA), adjust the DETECTOR ZERO by adjusting the detector internal ZERO
potentiometer (see the manual for the detector concerned).
Then, CONSECUTIVELY, adjust the measurement zero by acting on the ZERO potentiometer for
the measuring channel (Item A, Fig. 27) so as to read ZERO on the MX52 display panel.