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HMI (HUMAN-MACHINE INTERFACE)
The
HMI
(Human-Machine Interface) is available as an accessory to the
FieldLogger
. Several features are implemented
in this device, such as enabled channels monitoring, viewing these channels in chart mode, alarms monitoring, status
checking and configuration of some basic
FieldLogger
operation parameters.
Fig. 25
–
FieldLogger
with
HMI
The
HMI
is attached to the
FieldLogger
through a DB9 connector located under its cover. The
Fig. 10
and
11
demonstrate how the
IHM
is connected to
FieldLogger
.
Both power and serial communication go through the DB9 connector, so it is the only necessary connection. There is
also the possibility of using the
IHM
remotely, attached to the
FieldLogger
through an extension cable. As the
communication between
IHM
and
FieldLogger
is done through RS485 using a baud rate of 115200 bps what puts a limit
to the HMI operation distance is the power, what means that the voltage drop in the power cables (both positive and
negative cables summed) must be 0.4 V top. Considering a current consumption of 80 mA, it makes the maximum cable
resistance to be 5 ohms. As cable resistance per meter depends mainly on its section, we recommend checking a wire
resistance table. For some common cables, HMI’s maximum operation distance is shown in
Table 02
.
Gauge
Section
Maximum Length
24 AWG
0.21 mm
2
29 m
22 AWG
0.33 mm
2
47 m
20 AWG
0.52 mm
2
75 m
Table 02
– Wire resistance
Figure 26
below shows the pin-out needed to build an extension cable to the
HMI
.
Fig. 26
– Building an extension cable
PIN
SIGNAL
DESCRIPTION
1
-
-
2
+5 V
HMI
power input: +5 Vdc
3
-
-
4
B / D1 / D+ / D
RS485 Tx/Rx positive data
5
-
-
6
-
-
7
GND
HMI
power input: ground
8
A / D0 / D- / D\
RS485 Tx/Rx negative data
9
-
-
Table 03
– Pin-out for building the DB9 connectors
