Liquid Flow Meter SLQ-QT500

Versatile Liquid Flow Meter for up to 120 ml/min and Highly Viscous Fluids

The SLQ-QT500 features a flow range of up to 120 ml/min for water-based and hydrocarbon-based liquids, such as alcohols, solvents, oil, fuel and adhesives. It is the first choice for measurement of liquids containing particles or with a high viscosity. The SLQ-QT500 in combination with one of the SCC1 sensor cables can be easily integrated into demanding coating systems in the semicon industry, as well as into a wide array of dispensing and liquid flow systems in other industries.

The high sensitivity and measuring speed offers new possibilities for the monitoring and control of fast dispensing processes. The sensor is available with calibrations for H2O and isopropanol (IPA). Due to its micro-thermal measurement principle and large inner diameter, the measurement performance of the SLQ-QT500 does not depend on the viscosity itself, and so there is no strict upper or lower viscosity limit (e.g. kinematic viscosities of up to ~1000 mm2/s). It is also ideal for liquids that contain small particles, as long as they do not abrade the quartz glass tube.

For wetted parts, only PFA for the fittings and quartz glass for the inner flow channel have been chosen. As with all other Sensirion liquid flow meters, this reliable device has no moving parts and measures through the wall of a straight flow path.

The SLQ-QT500 liquid flow meter in combination with one of the SCC1 sensor cables offers a modular solution with a suitable electrical interface for almost any environment:

The SCC1-USB sensor cable provides a plug-and-play connection to a PC for operation with Sensirion’s viewer software or user-built programs for laboratory and desktop applications.
The SCC1-RS485 sensor cable featuring a stable RS485 interface and including advanced functionality such as dispense volume totalizer, automatic dispense detection, and data buffer for asynchronous read-out is designed for demanding industrial automation environments.
The SCC1-Analog sensor cable allows simple and quick readings or integration into generic controller systems without programming. In addition to a 0-10 V analog voltage output, the cable provides a configurable digital (high/low) output that can be programmed to act as a flow switch or pulse output.

Features

Maximum flow rate for hydrocarbons and water-based liquids: 120 ml/min

For high- and low-viscosity liquids or for liquids with small particles

Fast response time down to 50 ms

Highest sensitivity down to the lowest flow rates

RS485, USB, or 0-10 V analog voltage output

Straight flow path, no moving parts

Assured purity

Superb chemical resistance

Inert wetted materials: PFA and quartz glass

Maximum recommended operating pressure: 12 bar

Applications

High-end semiconductor process control

High-viscosity applications

Industrial automation

Fast dosing operations

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Related Discussion: Viscosity

The viscosity of a liquid describes its “thickness” or resistance to an external force. Low viscosity liquids include ether, acetone, gasoline, and water (kinematic viscosity ≤ 1.0 mm²/s). Medium range viscosity liquids typically are engine oils, vegetable oil, propylene glycol and photoresist. Common high viscosity liquids include, for example, grease, honey, high-viscosity photoresist, and adhesives. Typically, the viscosity of a liquid depends strongly on its temperature. Although the measurement performance of the SLQ-QT500 liquid flow meter does not depend on the viscosity itself, the sensor’s signal depends on the flow distribution inside the sensor tube and, in turn, the flow distribution depends on the viscosity. On the low-viscosity side, the flow rate is limited by fluidic effects, such as inlet conditions (e.g. changes in tubing diameters, bends in the inlet tube, etc.) and turbulence. On the high-viscosity side, the flow rate is limited by the tolerable pressure drop in the system. This limit depends heavily on the application.

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