CAUTION With the installation of
the equipment in Zone 0 Group II area it has to be ensured that sparks due to impact or
friction do not occur.
The cable glands and cables used for
wiring the device must not impair the Ex protection.
Unused lead-throughs must be sealed
using Ex compliant plugs.
Select a strain relief option that suits
the application (either use cable glands that include strain relief or install separate
clamps: see IEC 60079-14).
CAUTION Connect only de-energized
wires. Never switch on the power supply input before completing the wiring and closing the
The overvoltage category of HMT370EX
transmitters is I (non-mains equipment), and ambient pollution degree
is 4, as specified in IEC 60664-1. For intrinsically safe input parameters, see Table 1 .
Table 1. Intrinsically safe input
Associated apparatus entity parameters
Uo ≤ Ui
Io ≤ Ii
Po ≤ Pi
Co ≥ Ci + Ccable
Lo ≥ Li+ Lcable
Using analog output test points
There are test points for measuring the
voltages and currents of the analog outputs, located above each screw terminal block as
shown in Figure 1. Accessing the test points on the component board requires opening the
The transmitter body enclosure must not
be opened in an explosion hazardous area, unless a safe work permit has been issued in
accordance with the standard IEC 60079-14. Either remove the transmitter from the
hazardous area before opening the enclosure, or ensure that an IEC 60079-14 compliant
safe work procedure has been implemented in the hazardous area.
Use an intrinsically safe multimeter that won't cause the intrinsically safe input
parameters listed in Table 1 to be exceeded when it is connected in series (current
measurement) or parallel (voltage measurement) to the associated apparatus.
Using the service port
The service port (see Figure 1) must only be used in a safe area. Either remove the transmitter from the
hazardous area or ensure that a safe work procedure has been implemented in the hazardous
area. Only use the Vaisala accessory PC connection cable with the service port.
The probe (includes probe body and head) can
be detached and replaced by the user. The probe head filter (see Figure 1) is also user-replaceable. For other maintenance requirements,
CAUTION The probe can be detached
and changed when HMT370EX is powered. Any other live maintenance, including changing the
probe head filter, is not allowed.
The content in this chapter is
maintained in the following separately tracked document: