T/LL401 Capacitance Liquid Level Sensor for Oil or Coolant (Current output)

The T/LL401 4-20mA Oil or Coolant Level Sensor is a compact capacitive sensor designed to provide continuous and accurate fluid level monitoring in demanding industrial and mobile equipment applications. Suitable for both oil and coolant level measurement, the sensor is commonly used in engine oil sumps, hydraulic reservoirs, transmission systems, coolant tanks and expansion bottles. Delivering a configurable current output within the 0–20 mA range, typically specified as 4–20 mA, the T/LL401 provides reliable real-time level data for seamless integration with PLCs, engine control units, telematics systems and industrial monitoring equipment. If you need a Voltage output such as 0-5Vdc please check our T/LL400 version. With configurable current output options to suit individual application requirements, the sensor offers precise fluid level feedback across the full measurement range. Its robust solid-state design contains no moving parts, helping to improve reliability, minimise maintenance requirements and deliver accurate, repeatable measurements throughout the product’s service life. Continuous Oil and Coolant Level Monitoring Unlike traditional switch-based devices, the T/LL401 provides continuous fluid level measurement, allowing operators and control systems to monitor oil and coolant levels in real time. This enables predictive maintenance, reduces the risk of unexpected downtime and helps protect valuable equipment from damage caused by low fluid levels. Accurate Fluid Level Measurement Across Extreme Temperatures Designed for use in demanding environments, the T/LL401 delivers dependable performance across an extended operating temperature range of -40°C to +125°C (-40°F to +257°F). The sensor maintains excellent accuracy and repeatability, even when exposed to the temperature fluctuations commonly encountered in engines, transmissions, hydraulic systems and power generation equipment. Protect Equipment with Integrated Low-Level Alarm The integrated connector version of the T/LL401 includes a programmable low-level alarm output as standard. Factory configured to activate at 12.5% fluid level, the sink-to-ground alarm provides an early warning of low oil or coolant conditions. Alternative alarm points can be specified to meet individual application requirements, helping prevent costly equipment damage and unplanned shutdowns. Compact Sensor Design for Restricted Installation Spaces The T/LL401 features a slim vertically mounted design that occupies minimal space within the tank or reservoir. Available in lengths ranging from 80 mm to 300 mm, the sensor can be tailored to suit a variety of tank depths whilst maintaining excellent measurement performance. Its compact footprint makes the sensor particularly well suited to modern equipment designs where installation space is limited. Industry-Standard 4–20 mA Output The T/LL401 provides a robust current output signal, making it ideal for applications where long cable runs, electrical noise immunity and reliable data transmission are important. The widely adopted 4–20 mA output offers excellent compatibility with industrial control systems, PLCs, engine management systems and remote monitoring platforms. Current loop outputs are particularly beneficial in harsh environments where voltage-based signals may be susceptible to interference or signal degradation. Flexible Electrical Connection Options To simplify integration into OEM and aftermarket systems, the T/LL401 is available with either: Integral Packard-style connector Flying lead assembly with the option of adding customer-specified connector. There are options for the leads to exit the cable cap upwards or to the side to reduce height. These options provide flexibility when integrating the sensor into new or existing electrical architectures. Oil and Coolant Level Sensor Applications The T/LL401 is suitable for a wide range of fluid level monitoring applications, including: Engine oil sumps Hydraulic oil reservoirs Transmission oil systems Engine coolant tanks Coolant expansion bottles and tanks Generator set cooling systems Construction and agricultural machinery Commercial vehicles Industrial lubrication systems Power generation equipment Stationary industrial equipment Remote monitoring and telematics systems Why Choose the T/LL401 Oil and Coolant Level Sensor? The T/LL401 combines continuous level measurement, a robust 4–20 mA output signal, compact packaging and exceptional environmental performance in a single solution. Designed for accurate monitoring of both oil and coolant, it provides equipment manufacturers and system integrators with a dependable method of protecting critical assets, improving maintenance visibility and enhancing overall system reliability. Key Features Continuous oil and coolant level measurement Suitable for 9-36 Vdc power supplies Capacitive sensing technology with no moving parts Configurable current output from 0–20 mA Typical industry-standard 4–20 mA output Operating temperature range from -40°C to +125°C Compact vertical mounting design Sensor lengths available from 80 mm to 300 mm Integral connector or flying lead options Factory programmable low-level alarm output Suitable for engine oil, hydraulic oil, transmission oil and coolant applications Ideal for OEM, industrial, power generation and off-highway equipment Need Help Selecting the Right Sensor? Contact the Rochester Sensors team for assistance specifying sensor length, output configuration, alarm settings and connector options for your application.