Digital Input Modules; Phase Reversal; Line-Fault Detection (Lfd) - Eaton Crouse-Hinds MTL5500 Series Instruction Manual

6 .1
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.
6 .1 .1
Set the PR switch ON or OFF for the appropriate channel(s).
6 .1 .2
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:
•
•
•
•
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.
19

Digital Input modules

CH1
PR
Figure 6 .1: Switches to set LFD and phase reversal

Phase reversal

Line-Fault Detection (LFD)

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
1 2 3 4
OFF position
ON position
MTL5513, MTL5516
CH2
MTL5516C & MTL5517
LF PR LF
MTL5511 & MTL5514
- Ch 1 & 2
- Ch 1 only
INM 5500 Rev 11