Hach-Lange SC 100 - Manual (Page 26)

Wiring the Digital Gateway
22
Installation
3.6 Wiring the Digital Gateway
The digital gateway is designed to provide a digital interface to the sc100 controller (or other
appropriate digital controller). The non-sensor end is connected to the controller as described in
section 3.5.1 on page 19 for non-hazardous locations.
3.7 Connecting the Optional Digital Output
DANGER
Explosion hazard. Do not connect or disconnect electrical components or circuits to the
equipment unless power has been switched off or the area is known to be non-hazardous.
At this time, the manufacturer supports Modbus RS485, Modbus RS232, and Profibus DP
communication protocols. The optional digital output card is installed in the location indicated in
Figure 21 on page 23 . Terminal block J1 provides user connection to the optional network card.
The terminal connection is based on the selected network card. Refer to the instructions supplied
with the network card for more details.
Note: The sc100/1720E system also supports the AquaTrend Network.
Surge Protection Recommendation for Profibus DP
Many industrial environments are vulnerable to power transients and lightning. Water and
wastewater plants are notorious lightning targets. Lightning has become a leading cause of
instrument failure at these facilities. Surge protectors limit the magnitude of over-voltage transients
and protect equipment from damage. To be effective on Data lines, at a minimum, a surge
protector should provide two stages of protection with sub-nanosecond response time. Data line
surge protection should be installed on a Profibus DP network where it might be susceptible to
lightning or transients. The purpose of the surge protector is to protect the device (instrument) it is
located next to, not the network cable.
For the best performance/protection connect the surge protector as close as possible to the device
to be protected and connect the device (instrument) ground connection through the surge
protector’s ground to the local protective earth ground. Contact your local Profibus network
component supplier for their recommendation as to which surge protectors may be best for your
system.
Table 6 Digital Output Terminal Assignments
Terminal
Number
AquaTrend
Network 1
Modbus RS485
2-wire
Modbus RS485
4-wire
Modbus RS232 Profibus DP
1 Network A D+ RD+ Rx A1– (out)
2 Network B D– RD– No connection B1+ (out)
3 Network A No connection TD+ Tx A2– (in)
4 Network B No connection TD– No connection B2+ (in)
5 No connection Common Common Common Common
6 No connection No connection No connection No connection No connection
7 Shield Shield Shield Shield Shield
1 The AquaTrend Network only applies to sc100/1720E systems