Cognesense - Measure, Monitor, Protect

Captrol 520

The Captrol 520 is designed for refinery and chemical plant operators, wastewater and industrial process engineers, and OEM equipment designers who require reliable point-level detection in challenging tanks, silos, pits, and bulk storage applications.

The instrument delivers proven RF capacitance switching, universal power compatibility, and rugged probe configurations up to 250 ft in length.

Unlike mechanical floats, optical sensors, or vibrating forks that can foul, drift, or fail in viscous, abrasive, or sticky media, the Captrol 520 uses high-frequency RF technology, coating-rejection circuitry, and independent calibration controls. These features ensure accurate and repeatable switching even in low-dielectric liquids, powders, sludge, and slurries.

With fail-safe protection, adjustable time delay, and explosion-proof construction, the Captrol 520 is an effective solution for overflow protection, pump control, dry-run protection, and safety shutdown systems across oil and gas, chemical processing, water treatment, food production, and general industrial applications.

Captrol 520 RF Capacitance Point Level Switch

Details

The Captrol 520 detects material presence using RF capacitance sensing, measuring dielectric changes between the probe and the vessel wall.

A driven-guard probe design and coating-rejection circuitry allow the instrument to maintain accuracy even when material buildup occurs on the probe. This helps eliminate nuisance trips and reduces maintenance interruptions.

The universal AC/DC power input simplifies plant stocking and field installation, while fail-safe relay logic ensures safe system behavior for overflow protection, pump control, and shutdown systems.

Designed for harsh process environments, the Captrol 520 features explosion-proof enclosures, corrosion-resistant probe materials, and high-temperature and high-pressure probe options.

Flexible probe configurations including rigid probes, cable probes, and heavy-duty abrasion-resistant designs allow installation in chemical vessels, wastewater pits, bulk powder silos, and abrasive material transfer systems.

With decades of RF sensing development behind it, the Captrol 520 provides low-maintenance, long-life point level protection for critical industrial operations.

Technical Specifications

Parameter

Specification

Sensing Technology

RF capacitance (~2 MHz)

Power Input

115 VAC (95–135 V), 230 VAC (180–270 V), or 24 VDC (18–28 V)

Power Consumption

Less than 3 VA

Outputs

Up to two independent DPDT relays

Load Rating

5 A at 115 VAC; 2.5 A at 230 VAC; 3 A at 26 VDC (non-inductive)

Sensitivity

Adjustable; liquids ≥ 1.5 dielectric constant and solids ≥ 10 lb/ft³

Stability

0.01% per °F thermal stability

Time Delay

Fast response with adjustable delay from 50 ms to 10 seconds

Electronics Temperature Range

–40 °F to +160 °F (–40 °C to +71 °C)

Probe Rating

Up to 450 °F and 400–500 psi depending on probe type

Enclosure

NEMA 4, 5, 7, 9, 12

Hazardous Area Ratings

NEC Class I Groups C and D; Class II Groups E, F, G

Probe Types

Rigid, flexible cable, Teflon®, Kynar®, stainless steel, or Hastelloy

Probe Length

Up to 250 ft

Mounting

¾ in NPT or flanged connection

2026 COST ESTIMATE

Support

If you have questions not covered here, please contact the Cognesense support team for assistance.

What makes the Captrol 520 suitable for challenging media such as sludge or powders?

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Its 2 MHz RF sensing and coating-rejection circuitry ensure accurate switching even with buildup, foam, or low-dielectric materials.

Can the switch be used for both liquids and bulk solids?

Yes. The RF capacitance technology in the Captrol 520 is highly versatile. It’s sensitive enough to detect level changes in liquids (dielectric constant above 1.5) and is also effective for many bulk solids and powders (bulk density >10 lb/ft3).

Is the Captrol 520 approved for hazardous locations?

Yes — the housing is explosion-proof and approved for Class I & II hazardous areas.

What power supply options are available?

It accepts 115 VAC, 230 VAC, or 24 VDC, making it easy to standardize across facilities.

Can the device be used for pump control?

Yes — dual-point logic and adjustable time delay allow reliable pump-on/pump-off control to prevent short-cycling and overflow.

What is the benefit of the dual DPDT relay outputs?

The dual DPDT relays provide two completely independent switching circuits. This allows one Captrol 520 unit to handle two separate critical functions simultaneously, such as a high-level overflow alarm and a low-level pump shutoff, reducing the number of devices and tank penetrations required.

What probe lengths are available?

Probes are available up to 250 ft, ideal for tall silos and deep pits.

Does the Captrol 520 operate correctly in plastic or fiberglass tanks?

Yes — ground reference and probe options allow accurate sensing in non-metallic vessels.