6.7
Replacement and calibration of cassettes
When replacing a damaged or faulty electronics cassette, it is necessary to calibrate the
replacement cassette to the operating frequency of the fork sensor.
6.7.1
Replace the cassette
Prerequisites
If this replacement is taking place in a hazardous area, only qualified personnel should
perform the replacement. All work in hazardous areas must be carried out in accordance
to national and local codes of practice.
Calibration of this device is complex and it may take several attempts before success.
On Intrinsically Safe (I.S.) approved versions of the level switch, it is recommended that
replacement and calibration is performed in a non-hazardous (safe) area.
Note
•
In I.S. applications, NAMUR cassettes can only be replaced with NAMUR cassettes, and
8/16 mA cassettes can only be replaced by 8/16 mA cassettes.
•
Non-I.S. cassettes can be interchanged with other non-I.S. cassettes, but the new label
must be fitted and the original part number transferred to the new label.
•
Before starting the replacement and calibration procedure, ensure that any controlled
process will not be adversely affected.
Procedure
1. Isolate and disconnect the power to the Rosemount 2120, and insulate the ends of
the wires as a safety precaution.
There may be more than one power source connected to a relay cassette.
2. Remove the housing cover and disconnect the wires from the cassette.
Make a note of the connections and mode switch position (see
Figure 6-5: Mode Switch Setting (Existing Cassette)
This is an example of how the existing cassette may look. Here, the mode switch is
set to “Dry On” with a one second delay.
Take note of the actual setting.
SETTING IS: ____________________________________
3. Remove and retain the two fixing screws from the base of the cassette, and then
unplug the cassette.
Reference Manual
Service and troubleshooting
00809-0100-4030
March 2022
Rosemount 2120 Level Switch
61
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