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MTL Barries - MTL4575 - TEMPERATURE CONVERTER
(THC or RTD input + Alarm)
The MTL4575 is an intrinsic safety temperature converter that takes low-level signals from hazardous area sensors (like thermocouples or RTDs) and converts them into a standard 4/20mA current signal for safe-area control systems, isolating the zones by limiting energy to prevent explosions, using PC-based software for configuration, and featuring high accuracy and functions like line fault detection and alarms.
Here's a breakdown of its working principle:
- Signal Acquisition (Hazardous Area):
- It connects to temperature sensors (Thermocouples like J, K, T, or RTDs like Pt100) located in potentially explosive (Zone 0/Division 1) hazardous environments.
- It includes Cold Junction Compensation (CJC) for thermocouples, often via a dedicated plug, to ensure accuracy.
- Intrinsic Safety Isolation:
- The device uses techniques to limit the voltage and current passing through to the hazardous area, ensuring the energy level is below the ignition threshold for combustible gases.
- It acts as a barrier, isolating the hazardous zone from the safe zone, allowing each side to be earthed independently, which prevents ground loops.
- Signal Processing & Conversion:
- It receives the raw, low-level sensor signal (mV or resistance) and uses internal algorithms for linearization, ranging, and filtering.
- It converts this processed signal into a standard, robust 4/20mA current signal, which is ideal for long-distance transmission in industrial settings.
- Output & Alarms (Safe Area):
- The 4/20mA output drives a safe-area load (like a PLC or DCS input).
- It provides a configurable relay alarm output for process alarms or detecting sensor failures (like open circuits).
- Configuration:
- Users configure its features (sensor type, ranging, alarms) using PC software (MTL PCS45).
In essence, the MTL4575 safely bridges a temperature measurement from a dangerous area to a safe control system, ensuring both accurate measurement and explosion prevention.
| TEMPERATURE CONVERTER - THC or RTD input + Alarm |
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The MTL4575 is a single-channel, intrinsically safe
temperature converter and galvanic isolator that converts a low-level DC signal from a temperature sensor in a hazardous area into a proportional 4–20mA current for a safe-area load.
Its working principle involves three primary functions:
- Signal Conversion: The device accepts input from various temperature sensors, including different types of thermocouples (J, K, T, E, R, S, B, N) and 2-, 3-, or 4-wire RTDs (Pt100, Pt500, Pt1000, etc.). It processes this low-level voltage or resistance signal, performing linearization and ranging (which can be configured via PC software) to accurately represent the measured temperature value.
- Galvanic Isolation: This is a core function of the MTL4500 series. The unit uses innovative "One-Core" technology and isolating transformer construction to provide complete galvanic isolation between the hazardous-area field circuits and the safe-area control circuits. This isolation is critical for safety, as it prevents high voltages or energy surges in the safe area from reaching the hazardous area and potentially igniting flammable gases or dust. The design limits current and voltage in the hazardous area to intrinsically safe levels.
- Signal Transmission: The processed and isolated signal is output as a standard 4–20mA current signal, suitable for driving a safe-area load or connecting to a control system (DCS, PLC, etc.). It also provides a configurable alarm relay output for process alarms or sensor failure alerts (e.g., early burnout detection for thermocouples).
Configuration and monitoring are performed using a personal computer with MTL PCS45 software connected via a PCL45USB serial interface.
 Full Datasheet
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