INM 5500 Rev 11
19
6 .1 Digital Input modules
The Digital Input (DI) module range offers solid state or relay output switches in a safe area that
respond to input switches located in a hazardous area. Single or multiple channel (2 or 4) options
are available, as well as
Line-Fault Detection
(LFD).
Modules with LFD can recognise open or short circuit conditions on the input wires going to the
field sensors, and some DI modules have the facility to reverse the effect of the input on the
output
i.e.
phase reversal
.
These options are chosen with switches located on the edge of the module on the hazardous
area terminal side. In some applications it may be easier to set these switches
before
fitting the
module to the DIN-rail.
Figure 6 .1: Switches to set LFD and phase reversal
6 .1 .1 Phase reversal
Set the PR switch ON or OFF for the appropriate channel(s).
6 .1 .2 Line-Fault Detection (LFD)
Where fitted, set the LF switch ON or OFF for the appropriate channel(s).
Note
: LFD is
permanently active on the MTL5501-SR.
For all DI modules with LFD
except for the MTL5501-SR
; when using the LFD facility with a contact
input, resistors must be used. Fit 500Ω to 1kΩ (preferred value 680Ω) in with the switch and 20kΩ
to 25kΩ (preferred value 22kΩ) in parallel with the switch.
For modes of operation of the MTL5510 & MTL5510B that include LFD, resistors should be fitted as
described above.
For MTL5501-SR
use 1k4Ω in and 10kΩ in parallel with switch contact inputs.
For hazardous-area inputs conforming to EN 60947-5-6:2001 (NAMUR),
a line fault is judged by
the following rules:
•
Open circuit condition if hazardous-area current <50µA
•
Line integrity (no open circuit) if hazardous-area current >250µA
•
Short circuit condition if hazardous-area load <100Ω
•
Line integrity (no short circuit) if hazardous-area load >360Ω
Note
: the open circuit window (between 250µA and 50µA), and the short circuit window (between
100Ω and 360Ω), is not hysteresis. All MTL5500 modules, with inputs conforming to
EN 60947-5-6:2001 (NAMUR), will switch between open and complete circuit conditions within
these limits.
The MTL5501-SR LFD relay
de-energises
when a fault condition is detected. The MTL5514 and the
MTL5517
energise
the LFD relay to indicate a fault condition.
OFF position
ON position
1 2 3 4
CH1
CH2
PR LF PR LF
MTL5511 & MTL5514
MTL5513, MTL5516
MTL5516C & MTL5517
- Ch 1 & 2
- Ch 1 only
