Vaisala HMT370EX - Figure 15 FM Approved Wiring Diagram for Intrinsically Safe Operation

3.6.2.2 FM Approvals control drawing
Figure 15 (page 49) describes the FM Approvals requirements for intrinsic safety when wiring
HMT370EX series transmitters. The content in this section is maintained in Vaisala document
M212732EN.
HAZARDOUS AREA SAFE AREA
mA
V
mA
V
CH1
CH2
Test Points
Use FM approved associated apparatus;
zener barriers or galvanic separators
with entity concept parameters:
Voc < 28 V
Isc < 100 mA
C > C + C
L > L + L
+
−
+
−
NOTE:
1. Barrier installation must be
completed in accordance with
ANSI/ISA RP 12.6 and
the National Electrical Code.
2. Intrinsically safe barrier ground
must be less than 1 ohm.
3. Maximum safe area voltage (Um)
is 250 V.
The HMT370EX transmitter series has
the following approved probe options:
HMP371, HMP373, HMP374, HMP375,
HMP377, HMP378, and HMP378F/H
HMT370EX series transmitters are
approved for use in:
Class I, Division 1, Groups A, B, C, and D
Class II, III, Division 1, Groups E, F, and G
Class I, Zone 0, Aex ia IIC T4 Ga
Zone 20, Aex ia IIIC T85°C Da
Vmax=28 V
Load CH1
Vmax=28 V
Load CH2
HMT370EX connection board
i
i
cable
cable
The entity parameters for HMT370EX series transmitters are:
Vmax=28 V, Imax=100 mA, Ci=12.1 nF, Li=16 H, Pi=700 mW
Figure 15 FM Approved wiring diagram for intrinsically safe operation
Chapter 3 – HMT370EX regional safety certification information
49