MTL660 RANGE – INTRINSICALLY SAFE INDICATOR

The MTL660 Range – Intrinsically Safe Indicators (including MTL661, MTL662, MTL663, and MTL665) are digital indicators designed to display process variables in hazardous areas (such as Zone 0) and general-purpose plant areas. These indicators are specifically built for use in intrinsically safe systems, which are critical in environments where the risk of explosion or fire is present due to flammable gases, vapors, or dust.

Key Features of the MTL660 Range:

1. Intrinsically Safe for Hazardous Areas:

   • Designed for Zone 0, IIC, T4 hazardous areas.
   • These indicators comply with intrinsic safety standards, ensuring that electrical signals are kept below hazardous levels that could ignite flammable substances in dangerous environments.
   • The input circuit is intrinsically safe with parameters Ui = 30V, Ii = 200mA, Pi = 1.2W, Ci = 0nF, Li = 0mH, allowing safe operation in hazardous areas.

2. Loop Powered Display:

   • The indicators are loop-powered from the 4-20mA process signal, which means they draw power directly from the signal loop, minimizing the need for external power sources.
   • The low voltage drop allows installation in almost any 2-wire 4-20mA transmitter loop, which is common in industrial process control systems.

3. Display Characteristics:

   • 5½ digits (26mm height) for the process value, providing clear and readable values.
   • Eleven 8mm digits for displaying process units and current, offering both process data and units on the same display for easy monitoring.

4. Input and Output Range:

   • Input range: 4-20mA, typical for process control signals.
   • Over-range: The device can handle a maximum of 200mA without damage, which is a key feature in industrial environments where signal conditions can vary.

5. Operating Modes:

   • The indicator can operate in two modes: Linear or Square Root Extraction (software-selectable). Square root extraction is especially useful in flow measurement applications (e.g., using orifice plates, Dall tubes, or venturi meters) where the relationship between differential pressure and flow is non-linear.

6. Zero and Span Adjustment:

   • Zero and span can be set anywhere within the range, allowing flexible configuration based on application needs.
   • The scale direction (normal or reverse) is software-selectable, making it adaptable to various process requirements.

7. Accuracy:

   • The device has an accuracy of ± 0.01mA at 20°C, ensuring precise measurements and reliable operation.
   • Temperature effects on accuracy:
     • Zero: ± 0.0025% of span/°C.
     • Span: ± 0.01% of span/°C.

8. Environmental and Electrical Specifications:

   • Ambient Temperature:
     • Operating: –25°C to +70°C.
     • Storage: –40°C to +80°C.
   • Humidity: 5-99% RH, allowing operation in a wide range of environmental conditions.
   • Ripple Rejection: <0.01mA error with 1mA peak-to-peak ripple at 50Hz, ensuring stable readings in noisy electrical environments.

9. Out-of-Range Indication:

   • Displays “—– RANGE ERROR” for currents between 3.5 – 3.75mA.
   • Displays “99999 RANGE ERROR” for currents >22mA, helping identify abnormal or faulty signal conditions.

10. Backlight:

    • The unit includes a separately powered backlight that can be powered from an intrinsically safe power source with Uo = 28V, Io = 200mA, and Po = 0.96W max. This backlight is crucial for readability in low-light environments.

Applications:

• Mass/Flow Measurements: Used to retransmit and display mass or flow values from process control systems, particularly where differential pressure (e.g., from orifice plates, Dall tubes, or venturi meters) is involved.
• Process Control: Ideal for process variable monitoring in hazardous environments like chemical plants, oil & gas refineries, and pharmaceutical manufacturing.
• General Purpose: In addition to hazardous areas, the MTL660 indicators can also be used in general-purpose plant areas for accurate process monitoring.

Benefits:

• Intrinsically Safe: Ensures safe operation in explosive or hazardous environments, meeting international safety standards.
• Compact and Reliable: With a small voltage drop and flexibility in configuration, it offers a reliable solution for various process control systems.
• Flexibility in Operation: The ability to select between linear or square root extraction modes, along with adjustable zero and span, makes the device highly adaptable to different applications.