KROHNE CORIMASS G-MFM 4085 EEx EN - Manual (Page 5)

5
1.1 Description of the Transducer
The transducer MFS 4000-Ex is an intrinsically safe unit and contains three separated safe
circuits. These are:
−
Driver Circuit
−
Sensor Circuit
−
PT500 / Strain Gauge Circuit
The cables of these circuits are fed through the transducer housing via a special seal. There
are various transducer sizes available with different end connection options. Although standard
and E
E x transducers appear the same, in fact the E E x version has a longer converter mount
(neck) and also contains specific clamping diodes fitted across the driver coil. Therefore, it is
essential to avoid using a standard converter with E
E x transducer and vice versa.
In order to fulfil the Ex certification requirements, it is absolutely necessary to comply with the
technical data which is enclosed in this document. Under no circumstances should the process
fluid exceed 130
°
C, optional 150°C ( for instruments with zirconium tubes the max. temp. is
100°C) .
1.2
Description of the Converter
The Ex converter is available in two different versions:
a) The ‘de’ version
The electronics are placed in a pressure tight section of the converter housing, while the
termination compartment is not pressure tight. The converter housing may be fitted with
different cable glands such as NPT, PG16 or NPF glands for the mains supply and the
input/output cables. The protection class of the termination compartment in ‘e’.
b) The ‘d’ version
The electronics as well as the termination compartment are placed in a pressure tight housing.
The termination compartment is not fitted with any gland for the mains supply or the
input/output cables. The customer is responsible for fitting an Ex approved cable gland into
the PG16 thread of the housing. There are various suppliers for such cable glands on the
market. The protection class of the termination compartment is ‘d’.
For both cases the required waiting time between switching off the electronics and opening the
housing has to be considered. The waiting time is mentioned on the data plate of the system
and amounts to 25 minutes for T6 and 10 minutes for T5.
The Ex protection of the system is not valid if the electronics housing is not closed securely.
Make sure after opening the converter housing, to close it fully with the enclosed wrench.
The programming of the converter may also be performed with a closed lid by using the
enclosed magnet. Three magnet sensors are assembled on the display board, which allow the
user to operate the converter without touching the display itself.