Lower Cost Thermal Mass Flow Sensors with an Out of Liquid Element

Thin film mass flow sensors from IST AG offer solutions for a wide range of flow applications. The thin films and membrane technologies feature highly-accurate temperature sensors and heaters as main sensor elements.

The flow sensors from IST AG are suitable for gases (liquids upon request), can measure flow rates and directions from 0.0001 m/s (microflowSens) to 100 m/s (1mL/min to 10L/min respectively), and have operating temperature range from -30 °C to +450 °C. The sensors, in addition to measuring flow rates, are capable of detecting the presence of a liquid, bubble or biofilm as well as indicating liquid levels. The best possible adaptation of IST AG sensors is guaranteed by development channels in terms of response time, dynamic range, ambient conditions or directional detection.

Measurement Principle

Heat transfer principles are used by thermal mass flow sensors to determine a fluid’s flow velocity. Heat is carried from the sensor to the medium as the fluid passes through the sensor. This relationship depends upon the flow rate. As the flow increases, the amount of heat that is transferred also increases. If the temperature of the medium is known, the flow rate can be determined from the amount of voltage compensation required to maintain a constant temperature differential.

Out of Liquid

There are a handful of suppliers in the marketplace who offer thermal mass flow sensors and measuring systems in a wide range of products. Most of the designs are ready-to-use, compact systems that come with an outlet and inlet, and a channel including an active or a passive output. Such systems are adequate for many general-purpose applications, where the price and size of components are not very important; however, they are not appropriate for limited-space and price-sensitive flow control situations. In such cases, IST thermal mass flow sensor elements provide excellent solutions as well as the option to customize a wide range of parameters to meet customer’s requirements at a beneficial pricing.

IST AG’s new out of liquid element provides customers the flexibility of adapting the element to their applications and at a lower cost. Direct measurement of flow in a liquid channel has been shown to be a complex task without considerably reducing the lifespan and damaging the sensor due to debris and other similar contaminants in aggressive liquids

IST AG’s out of liquid element enables creating a go/no go application or with two elements to determine the flow through the channel, because of the external placement of the sensors. The principle used here is the proven and reliable thermal mass-flow measuring principle from IST AG.

Both a heater and a sensor chip with backside metallization are soldered onto the surface of the tube, providing an excellent thermal contact with the liquid without actually coming into direct contact with the liquid. This means that even aggressive liquids are appropriate for this element.

Technical Data *

. .
Measuring principle: thermal
Measurement range: 0 ml/min to 3000 ml/min
Warm up time:* < 30 s
Response time:* < 100 ms (0 to 1000 ml/min)
Temperature range (liquid):* -50 °C to +120 °C
Electrical connection: Cu/Ag wire, PTFE insulated AWG 30/19
Heater RH: (0 °C) = 50 Ω +/-1%
Reference sensor RS: (0 °C) = 1000 Ω +/-1%

*dependent on channel diameter, medium, used electronics etc.

Datasheet can be obtained upon request

This information has been sourced, reviewed and adapted from materials provided by Innovative Sensor Technology, USA Division.

For more information on this source, please visit Innovative Sensor Technology, USA Division.


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  1. Arun Jangam Arun Jangam India says:

    can it will be used for gasoline or equivalent material fuel.

    Arun jangam

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