MTL5045 MTL 5000 Series Analog Signal Isolator Current Loop Interface

MTL5045 | MTL 5000 Series 4–20 mA Hazardous-Area Signal Isolator

The MTL5045 transfers a 4–20 mA control signal from safe-area equipment to a load located in a hazardous area. Its single-channel design supports an output load of up to 800 Ω, delivering 16 V at 20 mA while keeping the input voltage drop below 4 V at 20 mA.

For control engineers, the key selection factors are loop compliance voltage, output load resistance, hazardous-area certification, and supply voltage. The MTL5045 also provides a green power LED, low signal ripple, and a specified transfer accuracy better than 20 µA at 20°C.

Signal Path at a Glance

Signal-path stage	MTL5045 function	Commissioning check
Safe-area input	Accepts a 4–20 mA signal, with an under/over-range span of 0–24 mA	Confirm controller output type, polarity, and available compliance voltage.
Isolation and transfer	Transfers the current signal through the isolator interface	Check supply voltage, wiring, and channel condition.
Hazardous-area output	Drives a load up to 800 Ω, rated at 16 V at 20 mA	Calculate the total loop load and confirm the receiving device's requirements.
Power indication	Green LED indicates power	Use the LED as a supply-status clue, not proof of correct signal transfer.

Electrical Specifications

Parameter	Specification
Model	MTL5045
Number of channels	One
Safe-area input signal	4–20 mA
Input under/over-range	0–24 mA
Hazardous-area output load	Maximum 800 Ω
Output drive capability	16 V at 20 mA
Output resistance	Greater than 2 MΩ
Input voltage drop	Less than 4 V at 20 mA
Input/output circuit ripple	Less than 40 µA peak-to-peak
Transfer accuracy at 20°C	Better than 20 µA
Temperature drift	Less than 1 µA/°C
Response time	Settles within 10% of final value in 250 µs
Supply voltage	20–35 V DC
Maximum current consumption	50 mA at 24 V; 60 mA at 20 V; 40 mA at 35 V
Maximum internal power dissipation	1.0 W at 24 V; 1.1 W at 35 V, with a 20 mA signal
Safety description	28 V, 300 Ω, 93 mA; Um = 250 V RMS or DC
Power LED	Green

Terminal Assignment and Wiring Reference

Use the terminal numbers below to verify the field wiring against the applicable MTL5045 installation drawing. Isolate the circuit and follow site safety procedures before changing connections.

Terminal	Function	Connection purpose
1	Output −ve	Negative output connection to the hazardous-area load circuit
2	Output +ve	Positive output connection to the hazardous-area load circuit
11	Input −ve	Negative safe-area current input
12	Input +ve	Positive safe-area current input
13	Supply −ve	Negative DC supply
14	Supply +ve	Positive DC supply

Wiring reminder: Do not interchange the input, output, and supply terminals. Confirm polarity and terminal numbering on the actual unit before energizing the circuit. The terminal table is a reference, not a substitute for the manufacturer's approved wiring diagram.

Load Selection: Check the 800 Ω Limit

The MTL5045 can drive a maximum load of 800 Ω at 20 mA, with a specified output capability of 16 V. The total load must include the receiving instrument and the resistance contributed by field wiring and other series components.

Example load	Voltage required at 20 mA	Selection implication
250 Ω	5 V	Below the specified maximum load
500 Ω	10 V	Below the specified maximum load
800 Ω	16 V	At the stated maximum output load
Above 800 Ω	More than 16 V at 20 mA	Outside the stated load rating; reassess the circuit design

Use Ohm's law to estimate the load voltage: V = I × R. At 20 mA, an 800 Ω load requires 16 V. Keep the total resistance within the specified limit and confirm that the receiving device can accept the resulting signal.

Where the MTL5045 Fits

• PLC or DCS analog output to a hazardous-area load: Transfers a safe-area 4–20 mA control signal to a suitable field load when the installation meets the required intrinsic-safety conditions.
• Control valves and field actuators: Potentially suitable for compatible current-driven devices whose required signal, load, and certification match the interface specification.
• Process-control skids: Provides a single-channel interface for analog control loops routed between safe and hazardous areas.
• Industrial signal-interface cabinets: Fits applications that require a defined 4–20 mA transfer path and a 20–35 V DC supply.

Confirm the field load type before installation. A 4–20 mA signal interface is not automatically compatible with every positioner, actuator, indicator, or transmitter. Verify whether the receiving device expects a current input, the required loop direction, and the applicable hazardous-area approval.

Hazardous-Area Suitability and Safety Parameters

The supplied specification identifies the load location as Zone 0, IIC, T4–T6 hazardous area when suitably certified, and Division 1, Group A hazardous location. The listed safety description is 28 V, 300 Ω, 93 mA, with Um = 250 V RMS or DC.

• Verify the exact MTL5045 certification and the approval applicable to the installation jurisdiction.
• Check the field device's entity parameters and the complete intrinsically safe loop design against the manufacturer's documentation.
• Confirm cable parameters, grounding requirements, and installation drawings before energizing the circuit.
• Do not assume that a generic model description alone establishes suitability for a particular gas group, temperature class, or Zone 0 installation.

Field Diagnostics: Symptoms, Causes and Checks

Observed symptom	Possible cause	Recommended diagnostic action
No output current	Missing supply, incorrect terminal wiring, open loop, or input signal absent	Check the green power LED, verify supply voltage at terminals 13 and 14, then measure the input signal using an approved method.
Output remains below the commanded value	Excessive loop resistance, incorrect polarity, or receiving-device loading	Calculate total loop resistance and confirm that the load does not exceed 800 Ω at 20 mA.
Reading fluctuates	Unstable controller output, loose connections, electrical interference, or poor wiring practices	Compare the safe-area input with the hazardous-area output and inspect terminals, cable routing, and shielding according to the installation design.
Current is correct at the input but incorrect at the load	Output-side wiring fault, excessive load, or a damaged interface	Check the output loop independently and compare measurements with the receiving instrument's input requirements.
Signal error changes with ambient temperature	Temperature drift or a temperature-related fault elsewhere in the loop	Compare the observed change with the specified drift of less than 1 µA/°C and inspect the complete loop before attributing the fault to the isolator.
Power LED is on but the signal is wrong	Input, output, polarity, load, or receiving-device issue	Remember that the LED indicates power only. Verify input current, output current, wiring, and load resistance separately.

Practical troubleshooting sequence: Verify the DC supply first, then measure the safe-area input, check the hazardous-area loop and total load, and finally confirm the receiving device's configuration. Follow hazardous-area procedures and use appropriately rated test equipment; never bypass required intrinsic-safety protection to troubleshoot a live circuit.

Global PLC Spare HUB's Insight

For the MTL5045, a common selection mistake is checking only the nominal 4–20 mA range without verifying the load and voltage budget. At 20 mA, an 800 Ω load requires 16 V, which matches the stated output capability. A higher resistance can prevent the output from reaching the commanded current.

• Validate the loop budget: Include the receiving device, cable resistance, and any other series elements when calculating total load.
• Separate supply checks from signal checks: A green LED confirms power indication, but does not prove correct current transfer.
• Use the terminal numbers carefully: Input, output, and supply connections have distinct terminal pairs. Verify polarity before energizing the unit.
• Confirm hazardous-area compatibility: Select the interface based on the complete loop approval and field-device requirements, not the area classification alone.
• Compare input and output measurements: This helps distinguish a controller-side issue from a load, wiring, or interface-side problem.

Global PLC Spare HUB can help customers review the part number, current-loop requirements, load resistance, and application details before ordering industrial automation interface components.

Warranty and Shipping

• Product condition: New, original item, subject to order confirmation and availability.
• Warranty: 12-month warranty against qualifying product defects, subject to applicable sales terms.
• Shipping methods: FedEx, UPS, and DHL, subject to destination and service availability.
• Order verification: Confirm the exact model, quantity, destination, and any required compliance documentation before dispatch.

Frequently Asked Questions

1. Can the MTL5045 drive a 4–20 mA load that requires more than 16 V at 20 mA?

The stated output capability is 16 V at 20 mA, corresponding to a maximum load resistance of 800 Ω. If the complete loop requires more voltage, the application falls outside the stated load capability. Recalculate the load and review the receiving device's input requirements before selecting an interface.

2. What is the practical difference between the 0–24 mA input range and the normal 4–20 mA signal?

The normal operating signal is 4–20 mA. The stated 0–24 mA range describes the specified under/over-range span, not a replacement for the normal control range. Confirm how the controller and receiving device interpret underrange and overrange values before using them for alarms or fault logic.

3. If the green LED is on, does that prove the hazardous-area output is healthy?

No. The green LED indicates power. It does not confirm that the input signal reaches the output correctly or that the load is within specification. Compare the input and output current, inspect terminal polarity, and verify the total loop resistance.

4. How should I choose this model for a control valve or positioner?

Start by confirming that the field device accepts a 4–20 mA current input and determine its required voltage and input resistance. Then check the total load against the 800 Ω limit, verify the required hazardous-area certification, and confirm whether the application needs this particular signal-transfer arrangement.

5. What should I provide when asking for a replacement or compatibility check?

Provide the full model number, controller or output-card model, receiving-device model, measured or specified loop resistance, supply voltage, hazardous-area classification, and wiring arrangement. These details help determine whether the interface fits the circuit and whether the required approvals and load limits are satisfied.

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