User manual

905U Wireless I/O Module User Manual
105S Serial I/O Module
Page 20 © October 2001
A 24VDC supply is available on the module for powering the analog transducer loops. In this case,
the analog loop should be connected between a "AI 1-" terminal and "COM" ( for the first analog input)
or "AI 2-" ( for the second analog input), and so on for other inputs. The positive terminal ("AI 1+" or
"AI 2+", etc) should be connected to "+24V".
Externally powered loops may be connected by connecting the input between "AI 1+" and “AI 1-” for
analog input 1 or "AI 2+" and “AI 2-” for analog input 2, and so on for other inputs. Analog Input 1
"AI 1+" may also be configured to control a high/low analog set-point. See Chapter 4 Configuration
for further details.
Common mode voltage may be -0.5V to 27V. Shielded cable is recommended for analog I/O loops to
minimise induced noise and Radio Frequency Interference (RFI). The shield of the cable should be
connected to earth at one of the cable only. The use of shielded wiring inside an enclosure containing a
module is also recommended.
2.4.5 Analog Outputs (905-1 and 905-3)
The ”-1” module provides two 4 - 20 mA DC analog outputs for connecting to instrument indicators for
the display of remote analog measurements. The ”-3” module provides eight 0 - 20 mA DC analog
outputs. Each analog output is a "sink" to common.
+
-
905U
A 24VDC supply is available on the module for powering the analog output loop (max external loop
resistance 1000 ohms). In this case, the analog loop is connected between a "+24V" terminal and "AO
1" ( for the first analog output) or "AO 2" (for the second analog output), and so on for the other output
signals.
Externally powered loops to 27 VDC may be connected by connecting the output between the "AO”
terminal (positive) and the "COM" terminal (negative). Zener protection of analog outputs provides
protection against short periods of over-voltage but longer periods may result in module damage.
Note that the common is connected internally to ground and no other point in the analog loop should
be grounded.
Analog outputs may also be configured to individually turn off (0 mA) if no command message is