Valcom T7L Series

What is it?

The T7L Series is a float-reed level transmitter designed for continuous and reliable liquid level measurement. It uses a float containing a toroidal magnet that moves along a guide tube. As the liquid level changes, the float activates a series of reed switches inside the tube, without any physical contact. These switching signals are processed by the electronics and converted into a standard 4–20 mA output with HART® digital communication.

Where is it used?

The T7L Series is used in a wide range of industrial applications, including chemical processing, water and wastewater treatment, oil and gas, marine systems, storage tanks, and process vessels. Its robust design makes it suitable for clean and moderately contaminated liquids, and for environments that require stable level monitoring even under demanding conditions.

How does it work?

As the liquid level rises or falls, the float moves along the guide tube. Inside the float is a toroidal magnet that actuates reed switches positioned inside the tube. Each change in reed switch status is detected by the transmitter electronics and converted into a continuous 4–20 mA signal with HART®. The system provides excellent repeatability and linear level indication regardless of the tank’s shape. With two floats, it can also function as an on/off level controller (5–15 mA output). The reed chain can be replaced without removing the transmitter from the tank and requires no recalibration. An optional PT100 sensor can be added to measure local fluid temperature.

What problems does it solve?

The T7L Series offers a reliable solution for level measurement where accuracy, repeatability, and long-term stability are essential. Its contactless magnetic operation minimizes wear and maintenance, while the ability to replace the reed chain without removing the instrument reduces downtime. The float-reed design provides linear and stable readings even in irregular tank shapes and ensures dependable performance in harsh industrial environments. Optional temperature measurement further increases its usefulness in process monitoring systems.

Electrical / Output

Supply voltage: 12.5 ÷ 30 V DC
Output signal: 4 ÷ 20 mA + HART® Rev 6
Alarm output (optional / on-off mode with two floats): 5 ÷ 15 mA
Alarm (standard): 3.85 mA / 21 mA
Maximum load for HART operation: 220 Ω < RL < 600 Ω (depending on supply voltage)

Level Measurement / Performance

Measuring range: 0.6 ÷ 10 m
Total accuracy (level readout): ± 5 mm under standard conditions
Measured-value update frequency (4–20 mA + HART): ≈ 1 s
Polling time (4–20 mA + HART): ≈ 800 ms
Response time (standard HART): < 256 ms
Adjustable damping (smoothing): 0 ÷ 60 s
Minimum specific gravity of fluid: 0.5 kg/dm³
Maximum allowed process pressure (standard version): up to 10 bar; special versions up to 50 bar
Long-term stability: < 0.1% FS per year

Operating & Environmental Conditions

Ambient (operational) temperature: –40 °C to +85 °C
Process temperature (standard): –40 °C to +85 °C
High-temperature version (finned body): –40 °C to +130 °C
Display head temperature (if applicable): –10 °C to +65 °C
Storage temperature: –40 °C to +90 °C
Ingress protection / housing rating: IP67 (AISI 316 housing) or IP66 (aluminum housing)

Mechanical / Process Connections & Construction Options

Float-reed measuring principle; inside the float is a toroidal magnet that operates reed contacts inside a guide tube.
When two floats are used, the transmitter can act as a level alarm (on/off), with output 5–15 mA.
Reed chain (sensor chain) can be replaced without removing the transmitter from the process, no recalibration needed.
Wetted parts and housing materials vary depending on configuration; options include AISI 316 stainless steel or aluminum housing; multiple float materials and densities for various media.

Certifications & Approvals

Certified per ATEX / Ex ia for hazardous areas (gas & dust zones): II 1G Ex ia IIC T6/T5 Ga and II 1D Ex ia IIIC T85°C/T100°C Da (depending on configuration).
Compliant with pressure equipment directive (PED 2014/68/EU) where applicable.
EMC compliant (EMC Directive 2014/30/EU).
Functional safety rating: SIL2 available depending on configuration.

T7L Series Datasheet

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