Section 3 Mechanical & Electrical Installation
16
FT742-SM (RS422 & RS485) Sensors
– User Manual
The O-ring compression fit is secured using 5x M3 fixings. The internal thread depth is 4.5mm, the length of
fixings should be determined taking into account the thickness of the mounting surface. Regular condition
monitoring of the sealing interface is recommended.
Caution
– Excessive length or tightening of the M3 screw may cause damage to the sensor thread.
3.1.2
Connector Details
All electrical connections are made to the digital sensor via an 8-way multi-pole connector located in the base
of the wind sensor housing. The connector pin designations are shown in Figure 6. The connector conforms to
IEC 61076-2-101.
Pin
RS422
RS485
FT009 Wire Colour*
1
0V
0V
Brown
2
6-30V
6-30V
White
3
TX Data A
N/C
Blue
4
RX Data A
Data A
Black
5
TX Data B
N/C
Grey
6
RX Data B
Data B
Pink
7
N/C
N/C
Violet
8
N/C
N/C
Orange
*Caution: Wire colours apply only to FT supplied FT009 cables. Other
cables may use different colour schemes, contact FT technologies for
further information.
Figure 6: Sensor Connector Pin
The FT742-SM sensor uses a M12 8-way male connector (ERNI Production GmbH, part number 464676).
Finished cable assemblies are available off-the-shelf as well as custom manufacture. The FT742-SM can use
up to 2A with the heater enabled, it is necessary to confirm all cables used are suitably rated for the operational
environment.
Care must be taken to ensure that the cable is suitable for the environment it will be used in and is adequately
rated and approved, for example AWM Style 21198. In an area with a moderate or severe lightning strike
exposure the cable may not provide sufficient EMI protection. In this case the cable will require further shielding,
for example being enclosed in a grounded metal pipe or conduit, or the use of sensors with a higher grade of
protection (for example the FT742-PM range).
The part FT009 is a 1.5m cable that can be used with the FT742-SM.
3.1.3
Lightning, Surge & EMI Protection
It is important to install the sensor and cabling with appropriate protection against lightning and other sources of
electromagnetic interference, in order to maximise its chance of survival and continued operation during and
after exposure.
The FT742-SM sensor is specifically designed for meteorological applications where the risk of lightning
exposure (indirect) is low.
All connections from the wind sensor to any data acquisition equipment and power supply should run through
suitable Surge Protection Devices (SPDs). This will suppress any unwanted overvoltage transients present on
the signal or power lines. The surge suppression devices are to be UL 1449 listed.
For areas where there is a high risk of lightning exposure (but still indirect) we would recommend the use of the
Pipe-Mount (PM) range of sensors. In such applications, the sensor body should be well grounded and the PM
variant of sensor is a more suitable solution. See the PM wind sensor User Manual for more details on this, or
contact FT Technologies for more information.
