Key Technical Specifications
| Parameter | Value |
|---|---|
| Channels | 2 |
| Signal Type | 4-20mA analog output |
| HART Support | Yes |
| Power Supply | 20-35 VDC |
| Current Consumption | 70mA |
| Galvanic Isolation | 250V rms (safe-area circuits to power supply) |
| Transfer Accuracy | Better than 20µA |
| Temperature Drift | <1.0µA/°C |
| Ripple | <40µA peak-to-peak |
| Response Time | Settles within 200µA of final value within 100ms |
| Min Load Resistance | 90Ω (short circuit detection at <50Ω) |
| Max Load Resistance | 800Ω (16V at 20mA) |
| Over Range | 24mA (load ≤520Ω) |
| Under Range | 1mA |
| Switching Frequency | 500 Hz to 10 kHz |
| SIL Rating | SIL2 and SIL3 per IEC 61508 |
| Hazardous Area Cert | IECEx/ATEX Zone 0 |
| Operating Temp | -20°C to +60°C |
| Storage Temp | -40°C to +80°C |
| Humidity | 5-95% RH |
| Mounting | T-section 35mm DIN rail |
| Dimensions (W×H×D) | 15.8mm × 118.8mm × 109.8mm |
| Weight | ~150g |
| Terminal Capacity | Up to 2.5mm² stranded or solid |
| LED Indication | Green power LED |
| Power Dissipation | 1.6W |
Product Introduction
MTL MTL5549 is a 2-channel 4-20mA HART isolating driver from the MTL5500 series, designed to interface control system outputs with field-mounted valve positioners in hazardous areas. It provides galvanic isolation between the safe-area control system and the Zone 0 hazardous-area field devices, with built-in line fault detection to flag open-circuit and short-circuit conditions.The module supports HART communication pass-through, making it suitable for smart valve positioner applications where both analog control and digital diagnostics are required. With SIL2/SIL3 certification under IEC 61508, it qualifies for use in safety instrumented functions up to SIL3 in a 1oo1 architecture. The compact 15.8mm width allows high packing density on standard 35mm DIN rail — a practical advantage in crowded marshalling cabinets.
Installation & Configuration Guide
Preparation — 10 min
- Confirm the module part number reads MTL5549 (or MTL5549Y if the Y-variant is specified).
- Verify the MTL5500 power supply rail (e.g., MPA5500) is installed and delivering 20-35 VDC.
- Confirm the 35mm DIN rail is grounded and mechanically secure.
- Prepare crimp ferrules for all field wiring (up to 2.5mm²).
- Have the loop drawing and I/O schedule ready for terminal assignment.
Removal (if replacing) — 5 min
- De-energize the power rail or isolate the specific channel.
- Label all wires before disconnecting.
- Release the module from the DIN rail using the spring clip.
- Pull the module straight off the rail.
Installation — 10 min
- Snap the MTL5549 onto the 35mm DIN rail until the retention clip engages.
- Connect power supply wires to the designated power terminals.
- Connect Channel 1 and Channel 2 input/output wiring per the loop drawing.
- Connect field-side wiring to the hazardous-area terminals (blue-marked).
- Verify all terminal screws are torqued and no stray wire strands are exposed.
Power-On & Test — 10 min
- Apply 20-35 VDC to the power rail.
- Confirm the green power LED illuminates.
- Inject a 4mA test signal on each channel — verify the field-side output reads 4mA ±20µA.
- Inject a 20mA test signal — verify output reads 20mA ±20µA.
- Simulate an open circuit on the field side — confirm line fault detection activates.
- Verify HART communication passes through using a HART communicator or AMS.
Troubleshooting Quick Reference
| Symptom | Likely Cause | First Check |
|---|---|---|
| No power LED | Power rail fault or module not seated | Measure 20-35 VDC at rail terminals |
| Output stuck at 1mA (under-range) | Open circuit on field side | Check field wiring continuity and valve positioner connection |
| Output stuck at 24mA (over-range) | Short circuit on field side | Disconnect field wiring and measure loop resistance |
| HART communication fails | Incorrect wiring or incompatible positioner | Verify HART-compatible positioner and correct terminal assignment |
| Output drift or noise | Power supply ripple or EMI | Measure supply ripple; check cable routing away from VFDs |
| Module does not seat on rail | Wrong rail type or damaged clip | Confirm T-section 35mm DIN rail; inspect retention clip |
Dimensions, Mounting & Wiring Notes
- Width: 15.8mm per module
- Height: 118.8mm
- Depth: 109.8mm
- Mounting: T-section 35mm DIN rail (snap-on)
- Wiring: Crimp ferrules required — accepts up to 2.5mm² stranded or solid conductors
- Power: Supplied via MTL5500 power rail (MPA5500 series) or direct 20-35 VDC
- IS wiring rule: Blue-marked terminals connect to hazardous-area field devices. Keep IS and non-IS wiring separated in cable trays.
FAQ
What is the difference between MTL5549 and MTL5549Y?
The MTL5549Y variant includes an open-circuit LED fault indication feature (the “Y” designation). Both are 2-channel 4-20mA HART isolating drivers, but the Y-variant provides additional visual fault status. Check your system specification to determine which variant is required.Can I use this module in a SIL3 safety loop?
Yes. MTL5549 is assessed for SIL2 and SIL3 per IEC 61508 in a 1oo1 (single-channel) safety architecture. However, the overall loop SIL rating depends on all components in the safety function — the sensor, logic solver, and final element must all be rated accordingly.Do I need a special power supply?
The module requires 20-35 VDC. The recommended approach is to use an MTL5500-series power rail (such as the MPA5500), which provides both power and fault monitoring across all modules on the rail. A standard 24VDC power supply within the 20-35V range will also work if wired directly.Is MTL5549 compatible with older MTL5000 series modules?
Yes. The MTL5500 series is designed to be backward-compatible with the earlier MTL5000 series for pluggable replacement. The mounting footprint and power rail interface are compatible.What happens if the field wiring breaks?
The module includes line fault detection. An open circuit on the field side will drive the output to under-range (1mA), which the control system can detect as a fault condition. The MTL5549Y variant also provides an LED indication.Can I hot-swap this module?
The MTL5500 series supports plug-in module replacement, but hot-swap capability depends on the specific power rail configuration and system design. Check with the system integrator or OEM documentation before attempting live replacement in a safety-critical loop.How do I verify HART pass-through is working?
Connect a HART communicator to the safe-area side of the module (across the output terminals). If the communicator detects the field device, HART communication is passing through correctly. If not, check wiring polarity and confirm the field device is HART-enabled.
