MTL MTL662-NA numerical guide for panel-mounted 4–20 mA indication in Zone 2 process systems
The MTL MTL662-NA is a panel-mount indicator that takes its operating power from the 4–20 mA signal loop. Its low loop burden, large process display and configurable engineering units make it suitable for analyzer panels, utility skids and local instrument cabinets where operators need a direct reading near the process.
Published operating data at a glance
| Input and power | 4–20 mA, loop powered; voltage requirement below 1 V |
| Main process display | 5½ digits with 26 mm-high characters |
| Secondary information | Eleven 8 mm characters for units and loop-current information |
| Ambient operating range | −25 to +70 °C |
| Storage and humidity | −40 to +80 °C; 5–99% RH |
| Over-range withstand | 200 mA maximum without damage |
| Construction | Panel style B, aluminium case, nominal weight 425 g |
Two quick calculations before commissioning
Loop-voltage example: with a 24 VDC supply, a transmitter requiring 12 V and an MTL MTL662-NA drop of less than 1 V, more than 11 V remains for the barrier, cable resistance and receiving input. This is an example calculation only; use the actual worst-case values from the project loop drawing.
Scaling example: if 4 mA represents 0 bar and 20 mA represents 10 bar, a 12 mA injection should display 5 bar. Verify at least the 4 mA, 12 mA and 20 mA points, then record the selected units, decimal position and password setting.
Where the -NA version changes the selection
The -NA designation permits installation in Zone 2 without an intrinsic-safety barrier or isolator when the complete installation complies with the applicable approval and wiring requirements. The final hazardous-area decision must still follow the delivered marking, control drawing and site classification; the product name alone is not an approval document.
Manufacturer reference: Eaton Crouse-Hinds MTL intrinsic safety solutions
