Function Expansion Unit FE260
12
Elster-Instromet
GmbH
3.3.1 Cables and cable lengths
The cable length between the FE260 and the volume corrector (intrinsically safe circuits)
may be up to 1000 m depending on the application. The following table provides an
overview of the requirements, settings and limits depending on the cable length:
Cable length up to:
10 m
100 m
500 m
1,000 m Rem.
Cable cross-sectional area for
power supply (Terminal “U”)
0.5 mm
2
0.5
mm
2
1.5
mm
2
1.5
mm
2
*1)
Max. transmission speed (Terminals
“R” and “T”)
19200 Bd 19200 Bd 19200 Bd 9600 Bd
*2)
Max. frequency on Outputs 1, 3, 4
(Terminals “DA1”, “DA3”, “DA4”)
10 Hz
10 Hz
1 Hz
1 Hz
*3)
Maximum frequency on Output 2
(Terminal “DA2”)
500 Hz
50 Hz
5 Hz
5 Hz
*4)
*1) For cable lengths up to 100 m a total of two cables 4 x 2 x 0.5 mm² are sufficient for all
intrinsically safe electrical circuits. With a cable length of more than 100 m a separate
cable 2 x 1.5 mm² must be laid for the power supply to the volume corrector (Terminal
“U”). The total diameter of each cable must not exceed 10 mm.
*2) The transmission speed is set on the volume corrector under “Bd.S2” (address
02:0708.0). With an FE260 with the option "Local interfaces" or "CL interface" the baud
rate must be set to 9600 Bd irrespective of the cable length. With "CL interface" also
lower baud rates are possible.
*3) With long cables (clearly noticeable from about 100 m) the pulse-space ratio is
degraded by the cable capacity: The space (output transistor blocking) is shortened
and the pulse (output transistor conducting) is lengthened correspondingly.
If this effect causes problems, the pulse duration and the period (and also therefore the
space duration) can be altered for the volume corrector outputs with the aid of the
“WINPADS” parameterising program.
Example:
The standard setting is: Period 1000 ms, pulse duration 500 ms (giving a space also of
500 ms).
With a cable length of 1000 m the space is typically shortened by about 250 ms and
the pulse is lengthened by about 250 ms. The space duration is therefore about 250
ms and the pulse duration about 750 ms.
If the (theoretical) pulse duration is set to 250 ms instead of 500 ms with the period
unchanged, then actual pulse and space durations each of 500 ms are produced again
including the degradations.
*4) Output 2 (“DA2”) can also be operated, as can all other outputs, as a low frequency
pulse output with a frequency up to 10 Hz, Furthermore, some volume correctors in the
LIS-200 range, such as the EK260
1
, offer the possibility of operating Output 2 as a high
frequency output at up to 500 Hz. The connection “DA2” on the FE260 is specially
rated for this. Consequently, the above mentioned degradation of the signal (see *3) is
substantially less here.
1
Only EK260s with a date of manufacture from July 2004 onwards.
