PRECISION DIGITAL Model PD662 loop-powered NEMA 4X meter can be equipped with an optional 24Vdc (11W Max) powered heater that allows it to operate in temperatures as low as -55C. The heater option is powered from a separate dc power supply and only draws power when required to keep the meter at approximately -20C. Suitable for applications where a simple, inexpensive display is required and ac power is not available. Device derives all its power from the 4-20mA loop. Device is scaled using four push buttons and can be done without applying an actual calibration signal.