MTL4573 Temperature Converter for THC and RTD Inputs
The MTL4573 accepts signals from thermocouples or RTDs mounted in hazardous locations. It then converts these low-level signals into a standard 4/20mA current for a safe-area load. This unit supports Zone 0, IIC hazardous areas and Division 1, Groups A-D locations. Additionally, you can select software features such as linearisation, ranging, monitoring, and testing. For thermocouple applications, the HAZ-CJC plug on terminals 1–3 includes an integral cold junction compensation sensor. Configuration requires a personal computer running MTL PCS45 software.
Key Input Specifications
The MTL4573 handles multiple input types. For thermocouple (THC) inputs, it supports types J, K, T, E, R, S, B, N following BS EN 60584-1:1996. It also supports type XK per GOST P8.585-2001. The minimum span is 3mV. For millivolt inputs, the range is -75 to +75mV with the same 3mV minimum span.
For RTD inputs, the MTL4573 works with Pt100, Pt500, Pt1000 (BS EN 60751:2008). Minimum spans are 10Ω, 50Ω, or 100Ω. It also supports Cu-50 and Cu-53 (GOST 6651-94) with a 10Ω minimum span. Ni100, Ni500, Ni1000 (DIN43760:1985) are available with 10Ω, 50Ω, or 100Ω minimum spans. For resistance inputs, the range is 0 to 400Ω with a 10Ω minimum span. RTD excitation current is 200µA nominal.
Output and Accuracy Performance
Output range is 4 to 20mA nominal into a 600Ω maximum load. You can select out-of-range characteristics as MTL or NAMUR NE43. Calibration accuracy at 20°C includes hysteresis, non-linearity, and repeatability. For mV and THC inputs, accuracy is ±15µV or ±0.05% of input value (whichever is greater). For Pt100 RTD inputs, accuracy is ±80mΩ. Output accuracy is ±11µA.
Temperature drift is typically ±0.003% of input value per °C for mV and THC inputs. For Pt100 RTD, drift is ±7mΩ/°C. Output drift is ±0.6µA/°C. Furthermore, common mode rejection is 120dB for 240V at 50Hz or 60Hz. Series mode rejection is 40dB for 50Hz or 60Hz.
Cold Junction Compensation and Sensor Failure
Cold junction compensation for THC input can be selected ON or OFF. Compensation error is ≤1.0°C. The MTL4573 provides safety drive on sensor failure with upscale, downscale, or off options. Early burnout detection is available for thermocouples when selected. EBD is indicated when loop resistance increases by more than 50Ω.
Communication and Indicators
A green LED indicates EBD alarm, power, and status. A yellow LED shows alarm conditions. Response time is typically 500ms. Maximum lead resistance for THC input is 600Ω. Maximum current consumption with a 20mA signal is 50mA at 24V. Power dissipation within the unit is 1.2W at 24V. Safety description parameters reference the certificate with Um=253V rms or DC.
Frequently Asked Questions (FAQ)
1. Can the MTL4573 work with both thermocouples and RTDs?
Yes, the MTL4573 supports both THC and RTD inputs. You simply select the sensor type during software configuration.
2. Does this unit provide cold junction compensation for thermocouples?
Yes, cold junction compensation is available and can be turned ON or OFF. The HAZ-CJC plug includes an integral CJC sensor.
3. What happens if the sensor fails or disconnects?
You can configure the MTL4573 for upscale, downscale, or off behaviour on sensor failure. Early burnout detection is also available for thermocouples.
4. What software do I need to configure the MTL4573?
You need a personal computer running MTL PCS45 software with a PCL45USB serial interface adapter.
5. Can I use this converter in Zone 0 hazardous areas?
Yes, the MTL4573 accepts signal sources located in Zone 0, IIC hazardous areas. The converter itself mounts in the safe area.
