FMT230, FMT250
THERMAL MASS FLOWMETER | CI/FMT230/250-EN REV. B
19
Changing the type of protection
The Modbus interface and the digital outputs of the models FMT230/250 can be operated with different types of protection:
• When connecting to an intrinsically safe circuit in Div. 1 as an intrinsically safe device (IS).
• When connecting to a non-intrinsically safe circuit in Div. 1 as a device with flameproof enclosure (XP).
• When connecting to a non-intrinsically safe circuit in Div. 2 as a non-sparking device (NI).
If a device that is already operational is operated with a different type of protection, the following measures must be
implemented/insulation checks performed in accordance with applicable standards.
Original installation
New installation
Necessary test steps
Housing: XP, U
max
= 30 V
Outputs non IS
Housing: XP
Outputs: IS
• 500 × 1.414 = 710 V DC/1min
Test between terminals A / B, 41 / 42 as well as 51 / 52 and the terminals A, B, 41, 42, 51 and
the housing. When this test is performed, no voltage flashover is permitted in or on the
device.
• Optical evaluation particularly of the electronic circuit boards, no visible damage or evidence
of explosion.
Housings: Div 2
Outputs: NI
• 500 × 1.414 = 710 V DC/1min
Test between terminals A / B, 41 / 42 as well as 51 / 52 and the terminals A, B, 41, 42, 51 and
the housing. When this test is performed, no voltage flashover is permitted in or on the
device.
• Optical evaluation particularly of the electronic circuit boards, no visible damage or evidence
of explosion.
Outputs: IS
Housing: XP
Housing: XP
Outputs: non IS
• Visual inspection, no damage visible on the threads (cover, ½ in NPT cable glands).
Housing: XP
Outputs: NI
• No special measures.
Housing: XP, U
max
= 30 V
Outputs: NI
Housing: XP
Outputs: IS
• 500 × 1.414 = 710 V DC/1min
Test between terminals A / B, 41 / 42 as well as 51 / 52 and the terminals A, B, 41, 42, 51 and
the housing. When this test is performed, no voltage flashover is permitted in or on the
device.
• Optical evaluation particularly of the electronic circuit boards, no visible damage or evidence
of explosion.
Housing: XP
Outputs: non IS
• Visual inspection, no damage visible on the threads (cover, ½ in NPT cable glands).
Note
For further details on explosion protection, types of protection and device models, refer to the installation diagram in the annex!
