HNL20-A Magnetic Float Liquid Level Sensor with 4–20 mA Output

The HNL20-A is a compact integrated level sensor that combines a built-in Hall effect magnetic element with an external magnetic float. As the float rises and falls with the liquid level, the sensor outputs a continuous analog level signal — not a simple point switch. An NBR float for oil or a 304 stainless-steel float for water is available, and a combined level-plus-temperature version can be ordered for equipment upgrade and retrofit projects.

INQUIRY

Continuous 4–20 mA Level Monitoring for Hydraulic and Machine Tanks

The slim rod sensor suits pumps and compressors, machine tools and machining centres, hydraulic and pneumatic systems, machinery manufacturing, automation equipment, hydraulic oil reservoirs, lubricant and coolant tanks, small oil and water tanks, mobile machinery fluid tanks and OEM level monitoring. DIN 43650 Hirschmann connector, 304 stainless-steel housing, IP65 protection.

Good fit: pumps and compressors, machine tools and machining centres, hydraulic and pneumatic systems, machinery manufacturing, automation equipment, hydraulic oil reservoir level, lubricant and coolant tank monitoring, small oil and water tanks, industrial equipment retrofit and upgrade, mobile machinery fluid tanks, OEM equipment level monitoring, process control panels.

Is HNL20-A Suitable for Your Application?

Choose HNL20-A when:

• You need a continuous analog level signal (4–20 mA) for display, control or dry-run protection, rather than a single alarm contact.

• The medium is hydraulic oil, lubricant, coolant or water, matched to the NBR or 304 float, within –20…85 °C.

• The measuring range fits 150…1000 mm and the tank opening accepts a G1, G1-1/2 thread or DN25 flange.

Confirm with us first when: the medium is strongly corrosive or aggressive, the level range exceeds 1000 mm, the tank is pressurized beyond the connection rating, or you need a separate continuous temperature transmitter in addition to the combined version.

Hall Effect Float Principle

Continuous level, not a point switch

The magnetic float moves along the guide rod; the internal Hall element tracks the float position and outputs a proportional 4–20 mA signal. Measurement accuracy 5 mm, long-term drift 5 mm, analog response ≤5 ms, with a 30 mm blind area at the rod end.

Two floats, two media; level or level-plus-temperature

NBR float for oil service; 304 stainless-steel float for water (the 304 float is available only with a G1-1/2 or larger external thread or a flange). Order product type 1 for level only, or type 2 for a combined level and temperature sensor.

Protected electronics for industrial mounting

DC16…30 V supply, short-circuit and reverse-polarity protection, insulation DC500 V, overvoltage DC36 V, switch-on time 2 s. 4…20 mA load ≤500 Ω. IP65, 304 housing and wetted 304/NBR parts.

Technical Specifications

Selection Code

Mechanical Dimensions

Guide-rod sensor with DIN 43650 head and magnetic float; rod length L matches the selected measuring range, with a 30 mm measurement blind area at the lower rod end.

Wiring and Installation

Connect the 4…20 mA loop to L+ and L–; the sensor supplies short-circuit and reverse-polarity protection. Mount through the G1, G1-1/2 thread or DN25 flange so the float slides freely along the rod, clear of the tank wall, strainer and internal baffle. Keep the 30 mm lower blind area in mind when setting the minimum readable level. Route the DIN 43650 cable away from vibration sources and hot surfaces, and seal the connector against moisture.

Typical Applications

• Pumps and compressors: reservoir level monitoring and dry-run protection.

• Machine tools and hydraulics: coolant, lubricant and hydraulic oil tank level.

• Machinery and automation: OEM equipment level monitoring and control-panel indication.

• Mobile and retrofit: mobile machinery fluid tanks, equipment upgrade and retrofit projects.

What to Send Us for Selection

Send: medium (oil/water) and temperature, tank size and required measuring range, available opening (G1, G1-1/2 or DN25 flange), float preference, whether temperature sensing is also required, and the receiving instrument or PLC analog input. We will confirm the selection code before quoting.

Frequently Asked Questions

Does this sensor measure continuous liquid level?

Yes. Unlike a point float switch, the Hall effect sensor tracks float position continuously and outputs a proportional 4–20 mA signal for level display and control.

How does float choice affect continuous measurement in water and hydraulic oil?

Use the NBR float for oil service and the 304 stainless-steel float for water. The 304 float requires a G1-1/2 or larger thread or a flange; match the float to the medium so it seals and moves correctly.

Can the 4–20 mA signal trigger pump dry-run protection?

Yes. Feed the analog signal to a PLC or controller and set a low-level threshold to stop the pump before suction loss; the same loop can provide high-level alarm.

What installation clearance keeps the magnetic float moving freely?

Leave clearance around the rod so the float does not touch the tank wall, strainer or baffle, and keep the lower 30 mm blind area in mind when locating the minimum readable level.

How often should buildup be removed from the guide rod?

Inspect and wipe the rod and float periodically in oil or coolant service; remove sludge, residue and waxing deposits that could bind the float. Frequency depends on medium cleanliness.

Datasheet Download

HNL20-A Magnetic Float Level Sensor Datasheet (PDF) — view all product manuals on our Download page »

Need a Continuous Level Sensor?

Send us the medium, range, opening and instrument input. We will confirm the float, connection and selection code before we quote.

Send us your application details »