Source: http://www.flow-network.com

WHAT IS THE CALORIMETRIC PRINCIPLE?
The calorimetric principle is a means of monitoring flow rates through thermal energy dispersion.
Typically the measurement involves two PTC thermistors embedded in the probe tip or wall of the sensor. One of the PTC thermistors (the reference thermistor) monitors the temperature of the medium being measured (air, water, oil, etc.) while the other is heated a fixed percentage above the reference thermistor. This sets up a differential resistance between the two.

Assume now that the probe tip is sitting in still air in a pipe or duct. The differential resistance is established by the electronics and everything remains stable until flow begins to occur. When this happens, the flowing air cools the heated thermistor, thus changing the differential resistance between the two thermistors, proportional to the flow speed. The amount of energy that the electronics uses to attempt to maintain the established differential resistance (by increasing power to the heater of the dynamic thermistor) is used to determine the flow rate. This is then translated into a switching or transmitter output.

“Calorimetric” thus can be described as measuring flow through use of “thermal dispersion” (think of the term “calorie” or unit of heat.)

For further information on the calorimetric principle see the following article at our website
http://www.flow-network.com/leak_detection.html

3000 SERIES VENT-CAPTOR

Flow rates as low as 0-3 ft per second or as high as 0-200 ft per second, the 3000 series air flow switches and transmitters address applications that other technologies can’t. Eliminate sticking or breaking or bending of the air sensor, so common with sail switches or other mechanical air flow monitors. Simple to install In stock with SAME DAY Shipping

Additional advantages of the 3000 series vent-captor are:

• Can not be damaged by too high an air flow as can mechanical types
• Repeatability <1% as there is no friction or mechanical hysteresis
• Self compensate for changes in pressure (mass flow unit)
• Small, space saving, compact design
• Simple to install
• AC or DC ranges (switches and transmitters)
• Self contained, no auxiliary amplifiers or linearizers needed.

Common Applications

• Sensing cooling airflow to cabinets or electronic housings
• Fume hoods in industrial applications such as soldering stations
• Air Handling equipment, dust collection systems
• Monitoring filter conditions – signal when change is needed
• HVAC systems for air balancing or flow detection
• Air circulation proving in rail and other transportation industries
• Compressed Air flow monitoring
• Call us today and let us help you with your air flow monitoring application.