KAL-A - Thermal Flow Sensor for Water-Based Liquids

Economical Thermal Flow Sensor for Water-Based Liquids

The KOBOLD KAL-A is a calorimetric thermal flow sensor for water-based liquids that uses microprocessor-based temperature compensation to hold its flow reading steady as media temperature changes. It is designed for reliable, continuous flow monitoring in industrial and sanitary water lines, from cooling circuits to clean-in-place process piping, according to specifications.

This flow sensor features a compact stainless-steel probe with no moving parts, ensuring durability at pressures up to 1450 PSIG (100 bar). It supports velocities from 0.2 ft/s to 6.6 ft/s (0.06 m/s to 2 m/s), corresponding to flow ranges as low as 0.08 GPM (0.3 L/min) in 1/2-inch pipes. Made in the USA, the KAL-A includes NPT or Tri-Clamp fittings for seamless integration, with an IP65-rated housing.

The KAL-A helps optimize processes by delivering a linear 4-20 mA output proportional to flow, while maintaining extremely low pressure loss, typically under 0.5 psi at standard velocities.

How the KAL-A Works: Calorimetric Measurement Principle

The KAL-A measures flow by warming its probe slightly and tracking how quickly the passing liquid carries that heat away. The measured cooling rate corresponds to flow velocity, and full microprocessor compensation reduces drift from temperature changes across 0°F to 176°F (-18°C to 80°C), according to specifications.

During the first 0.8 seconds of the measuring cycle, the probe is heated above the media temperature. As liquid flows past, it cools the probe; the rate of cooling, measured at 1.8 seconds, is compared to an internal lookup table specific to the ambient temperature recorded at the start of the cycle. Validation occurs at 5.6 seconds, so a reading passes through only when the probe returns to baseline; otherwise the sensor waits an additional 5.6 seconds and repeats the check. Typical response time is 5.6 to 12 seconds.

The flow rate is transmitted via a 4-20 mA analog signal, an 8-LED trend display provides real-time visualization, and optional PNP/NPN switching (up to 400 mA) enables set-point alert or alarm functionality.

Key Features and Performance Advantages

The KAL-A is engineered for hygienic and industrial reliability: 3-A compliant sanitary fitting options and a smooth probe surface that prevents buildup help reduce cleaning downtime, while the compact electronics support easy field calibration for custom ranges, according to specifications.

• Microprocessor-based temperature compensation for negligible drift
• No moving parts to minimize failure risk and pressure loss
• Probe insensitive to dirt and debris
• Quick set-up with potentiometer adjustments
• 8-LED trend display for at-a-glance flow status
• Optional fail-safe PNP/NPN switch with bi-colored LED indicator
• 3-A sanitary fittings for food and beverage compatibility

KAL-A Technical Specifications Overview

Key values from the current datasheet: the KAL-A operates on 24 VDC, covers water velocities of 0.2 to 6.6 ft/s across pipe sizes from 1/2 inch to 20 inches, and is offered with threaded connections in two stainless-steel grades or a 3-A compliant sanitary connection.

• Measuring principle: calorimetric (thermal)
• Output: 4-20 mA, 3-wire, into a maximum 500 Ω load; optional PNP/NPN open-collector switch, 400 mA max
• Linearity: ±10% of full scale; Repeatability: ±1% of full scale
• Velocity range: 0.2...6.6 ft/s in water-based liquids
• Operating pressure: 1450 PSIG max (NPT); up to 600 PSIG or per clamp rating (sanitary Tri-Clamp)
• Media temperature: 0...176°F operating; CIP 280°F non-operating
• Ambient temperature: -4...140°F
• Response time: 5.6...12 seconds typical
• Materials: probe and wetted parts 304 SS (1/2" NPT), 316-Ti SS (1/2" or 3/4" NPT), or 316L SS (Tri-Clamp); housing glass-fiber reinforced polyamide
• Power supply: 24 VDC ± 2 VDC; maximum current draw 300 mA
• Electrical connection: cable gland or optional M12 plug connector
• Protection: IP65
• Process connections: 1/2" and 3/4" NPT or 1-1/2" Tri-Clamp (3-A compliant)

Common Questions about KAL-A - Thermal Flow Sensor for Water-Based Liquids