MTL5081 Eaton MTL | Isolated Millivolt Repeater Thermocouple Isolator
Introduction:
The MTL5081 is an isolated millivolt repeater for thermocouples and mV sources. It features selectable safety drive on burnout with upscale/downscale.
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Eaton MTL5081 Isolated Millivolt Repeater for Thermocouples
Product Overview
A precision isolated repeater arrives as the MTL5081 from Eaton's MTL series. This device takes low-level DC signals from hazardous-area voltage sources. The MTL5081 isolates these signals and passes them to safe-area instruments. Engineers use this module primarily with thermocouples requiring external cold junction compensation. Consequently, the MTL5081 suits Zone 0, IIC, T4-T6 hazardous areas when certified. The unit features two switches for configuring safety drive during burnout conditions. Furthermore, a green LED provides clear power indication for quick diagnostics.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Eaton (MTL) |
| Model | MTL5081 |
| Product Type | Isolated Millivolt Repeater |
| Number of Channels | 1 |
| Signal Source | Any DC millivolt source |
| Location of mV Source | Zone 0, IIC, T4-T6 / Div. 1, Group A |
| Input/Output Signal Range | 0 to ±50mV (±55mV overrange) |
| Output Resistance | 60Ω nominal |
| Linearity/Repeatability | <0.05% of reading or ±5µV (greater) |
| Temperature Drift | ±(2µV + 0.002% of input)/°C |
| Response Time | <150µs (to 10% of final value) |
| Frequency Response | DC to 4kHz |
| Power Requirement | 20mA max, 20 to 35V DC |
| Power Dissipation (24V) | 0.5W |
| Power Dissipation (35V) | 0.7W |
| Isolation | 250V AC between all circuits |
| LED Indicator | Green (power) |
Terminal Functions
The MTL5081 uses clearly numbered terminals for straightforward wiring.
| Terminal | Function |
|---|---|
| 1 | THC/mV input –ve |
| 2 | THC/mV input +ve |
| 11 | Output –ve |
| 12 | Output +ve |
| 13 | Supply –ve |
| 14 | Supply +ve |
This clear terminal assignment simplifies installation and troubleshooting. Input terminals 1 and 2 accept any DC millivolt source including thermocouples. Output terminals 11 and 12 connect to safe-area receiving instruments. Supply terminals 13 and 14 accept 20 to 35V DC for flexible power integration.
Input and Output Signal Range
The MTL5081 accepts a wide range of low-level DC signals. Input range spans 0 to ±50mV for standard thermocouple and mV sources. Overrange capability extends to ±55mV for signal fluctuations. Thus, the MTL5081 accommodates all common thermocouple types. Output resistance measures 60Ω nominal for driving receiving instruments.
The device preserves signal integrity across the isolation barrier. Output signal mirrors the input within specified accuracy limits. Therefore, control systems receive faithful representation of hazardous-area measurements.
Transfer Accuracy
The MTL5081 delivers exceptional accuracy for precision temperature measurement. Linearity and repeatability stay below 0.05% of reading or ±5µV. Thus, the MTL5081 preserves thermocouple measurement integrity across isolation. This accuracy suits demanding applications like furnace monitoring and chemical reactors. Typical performance exceeds these specifications for most operating conditions.
The device maintains calibration without frequent recalibration cycles. Therefore, maintenance costs stay low throughout the MTL5081 lifecycle. For critical applications, periodic verification remains recommended.
Temperature Drift
The MTL5081 exhibits excellent stability across changing ambient temperatures. Temperature drift equals ±(2µV + 0.002% of input) per degree Celsius. Thus, accuracy remains stable even in unheated control rooms. For a 10mV input signal, drift equals ±2.2µV per degree Celsius. Therefore, the MTL5081 suits outdoor installations and variable environments.
This low drift performance matches high-quality thermocouple measurement requirements. Consequently, the MTL5081 does not introduce significant errors beyond thermocouple limits. Thus, system accuracy remains limited primarily by the sensor itself.
Response Time and Frequency Response
The MTL5081 responds rapidly to input signal changes. Settling reaches within 10% of final value in under 150 microseconds typically. Thus, the MTL5081 captures fast temperature transients effectively. Frequency response extends from DC to 4kHz for dynamic measurement applications. Therefore, this repeater suits not only slow temperature changes but also faster process variations.
For most thermocouple applications, response is effectively instantaneous. Control loops experience negligible delay from the MTL5081. Thus, system stability remains unaffected by this isolation repeater.
Safety Drive on Thermocouple Burnout
The MTL5081 includes two switches on top of the module for burnout configuration. First, an enable/disable switch turns safety drive on or off as needed. Second, an upscale/downscale switch selects the drive direction during burnout. Thus, the MTL5081 allows users to choose the safe output state. This feature proves critical when thermocouple breakage could create unsafe conditions.
When enabled, safety drive forces the output to a known extreme value. Upscale drive forces the output high when a burn out occurs. Downscale drive forces the output low under the same condition. Therefore, control systems can detect sensor failure and respond appropriately.
The safety drive feature is entirely configurable by the user. Switches are accessible on the module top without removing the unit. Thus, the MTL5081 adapts to different application safety requirements easily.
Thermocouple Compatibility
The MTL5081 is intended for use with thermocouples utilising external cold junction compensation. External compensation allows use of high-accuracy reference junctions. Thus, the MTL5081 does not provide internal cold junction compensation. Engineers must provide compensation external to the module for thermocouple measurements.
Any DC millivolt source can connect to the MTL5081 input. Therefore, the device also suits other low-level voltage signals. Strain gauges, pressure sensors, and other mV-output devices work equally well.
Power Requirements
The MTL5081 requires 20 to 35V DC supply voltage for operation. Maximum current consumption reaches 20mA across the full supply range. Thus, the MTL5081 consumes very little power for an isolated device. Power dissipation ranges from 0.5W at 24V to 0.7W at 35V. Therefore, multiple MTL5081 units can be mounted without significant heat buildup.
Low power consumption reduces panel cooling requirements. Consequently, the MTL5081 suits dense installations in control cabinets. The 20mA maximum current simplifies power supply sizing for large systems.
LED Indicator
The MTL5081 includes a green LED for power status indication. This LED illuminates when supply voltage is present and correct. Thus, technicians can verify power instantly without test equipment. A dark LED indicates missing or insufficient supply voltage. Therefore, troubleshooting starts with checking the green LED on the MTL5081.
No additional LEDs exist for signal status on this model. For signal diagnostics, use external indicators or control system monitoring. Thus, the MTL5081 maintains simplicity while providing essential power indication.
Isolation Specifications
The MTL5081 provides full three-port isolation for maximum safety. Isolation withstands 250V AC between safe circuits, hazardous circuits, and power supply. Thus, the MTL5081 protects safe-area equipment from hazardous-area transients. This isolation level meets stringent industrial safety requirements for IS barriers.
The safety description for terminals 1 and 2 is non-energy-storing apparatus. Parameters are ≤1.2V, ≤0.1A, ≤20µJ, and ≤25mW. Thus, thermocouples and mV sources can connect without further certification. Any IS loop with open circuit voltage below 28V accepts the MTL5081 input.
Hazardous Area Compatibility
The MTL5081 suits demanding hazardous area installations globally. Millivolt source can locate in Zone 0, IIC, T4-T6 hazardous areas under IEC standards. North American Div. 1, Group A hazardous locations are also acceptable. Thus, the MTL5081 serves both IEC and NEC classified areas for gas groups A and IIC.
The device must be suitably certified for the intended installation. Always verify that your MTL5081 version matches area classification requirements. Therefore, consult the certificate documentation before hazardous area installation.
Installation Guide
Follow these steps to install the MTL5081 correctly.
Power Down System: De-energize all circuits before installation begins.
Mount Unit: Secure the MTL5081 to DIN rail in a safe-area enclosure.
Connect Supply: Wire 20-35V DC to terminals 13 (-ve) and 14 (+ve).
Verify Green LED: Check that power indicator illuminates correctly.
Set Burnout Switches: Configure safety drive enable and upscale/downscale.
Wire mV Source: Connect thermocouple or mV source to terminals 1 and 2.
Wire Output: Connect safe-area receiving instrument to terminals 11 and 12.
Verify Compensation: Ensure external cold junction compensation is provided.
Test Operation: Apply mV signal and verify output matches input accurately.
Important: Never apply voltages exceeding ±55mV to the MTL5081 input terminals. Always maintain proper segregation between hazardous and safe wiring. The device provides 250V AC isolation, but physical separation remains best practice. Finally, provide external cold junction compensation for thermocouple applications.
Key Features and Benefits
Precision Accuracy: Delivers <0.05% linearity and repeatability for critical measurements, ensuring reliable data.
Fast Response: Settles within 150µs for dynamic process monitoring, capturing temperature transients.
Selectable Burnout Drive: Configurable safety drive with upscale/downscale selection, enabling fail-safe operation.
Wide Signal Range: Accepts 0 to ±50mV for all thermocouple types and mV sources, providing versatility.
Low Power Consumption: Draws only 20mA maximum for energy-efficient operation, reducing panel heat.
Zone 0 IIC Compatible: Suits highest risk hazardous areas including hydrogen, enabling petrochemical use.
The MTL5081 delivers precise isolated millivolt repeat for thermocouple applications. Consequently, this repeater suits Zone 0 IIC hazardous areas requiring accurate temperature measurement. Its accuracy of <0.05% ensures reliable process data, while temperature drift stays within ±(2µV + 0.002%)/°C. The response time of 150µs captures fast transients, yet frequency response extends to 4kHz. Environmental compatibility includes Zone 0, IIC, T4-T6 hazardous areas for global installations.
Package Contents
One MTL5081 isolated millivolt repeater module
One terminal label sheet
One installation instruction sheet
Frequently Asked Questions (FAQ)
1. What thermocouple types work with the MTL5081?
The MTL5081 works with any thermocouple type producing a DC millivolt signal. External cold junction compensation must be provided separately. Thus, J, K, T, N, R, S, and B types are all compatible.
2. How does the safety drive function during thermocouple burnout?
Two switches on the MTL5081 top configure safety drive behavior. One switch enables or disables the safety drive function entirely. The second switch selects upscale or downscale output during burnout. Thus, you choose the safe output state for your application.
3. What hazardous area locations does the MTL5081 support?
The MTL5081 supports Zone 0, IIC, T4-T6 hazardous areas under IEC standards. For North America, Div. 1, Group A hazardous locations are acceptable. Thus, this device suits hydrogen, acetylene, and other IIC gas groups.
4. Does the MTL5081 require external cold junction compensation?
Yes, the MTL5081 is intended for use with external cold junction compensation. It does not provide internal compensation for thermocouple measurements. Therefore, you must add compensation external to the module for accurate temperature reading.
5. What is the response time of the MTL5081?
The MTL5081 settles to within 10% of final value in under 150 microseconds. Thus, this repeater captures fast temperature transients effectively. Control loops experience negligible delay from the MTL5081.