The EcoStruxure Transformer Expert falls into the SELV category (Safe Extra Low Voltage) - UL 60950, which states that no electrical safety certificate is needed for equipment that operates at or below 48 volts.
The EcoStruxure Transformer Expert sensor complies with this regulation as it is powered at 24 volts and generates no secondary voltages. As a result, it is considered intrinsically electrically safe and there is no requirement to mark UL on the product.
The EcoStruxure Transformer Expert sensor is shipped standard with a 230/100 to 24-volt DIN-mounted power supply, which carries its own UL, CE, and other marks. The attached specification of this power supply details these marks.