Blue Sea's M2 OLED Tank Monitor measures essential electrical system parameters with adjustable alarms and an auto-dimming display. This meter is compatible with common sending units.Includes a MOSFET External Circuit Relay (ECR), which can be used to control external circuits based on any value measured by the M2Can monitor up to four (4) tanks with intuitive tank-level monitoring and auto-calibration for unique tank shapesIncludes external DC Shunt or AC Current Transformer when required