{"id":40901,"date":"2024-05-13T22:11:24","date_gmt":"2024-05-13T22:11:24","guid":{"rendered":"https:\/\/www.alicat.com\/?post_type=article&p=40901"},"modified":"2026-01-23T18:12:00","modified_gmt":"2026-01-23T18:12:00","slug":"mems-thermisches-massenstrommessgerat-arbeitsprinzip","status":"publish","type":"support","link":"https:\/\/www.alicat.com\/de\/support\/mems-thermal-mass-flow-meter-operating-principle\/","title":{"rendered":"Thermischer Durchflussmesser - Arbeitsprinzip\u00a0"},"content":{"rendered":"\n[et_pb_section fb_built=”1″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_row _builder_version=”4.24.2″ _module_preset=”default” min_height=”134px” custom_margin=”-1px|auto||auto|false|false” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.23.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_heading title=”Thermal Flow Meter \u2013 Operating Principle ” _builder_version=”4.25.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_heading][et_pb_text _builder_version=”4.25.1″ _module_preset=”default” custom_margin=”||||false|false” global_colors_info=”{}” theme_builder_area=”post_content”]

MEMS (micro-electromechanical systems) thermal flow meters use thermal heating elements, temperature sensors, and thermal properties of a gas to measure mass flow rates.<\/span>\u00a0<\/span><\/p>\n

At its simplest, a thermal flow meter consists of a heating element and temperature sensors. There are two ways to utilize this setup: directly in the main flow path, or in a bypass tube.<\/span>\u00a0<\/p>[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”3_5,2_5″ use_custom_gutter=”on” gutter_width=”3″ _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”0px||||false|false” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”3_5″ _builder_version=”4.25.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]

What are the types of thermal flow meters?<\/h2>\n

For low flow rates, placing the sensor and heating elements in the flow path is most advantageous, as minimal heat is required and the sensors directly measure the temperature effects on the total flow. This direct measurement achieves higher accuracy than that of a bypass meter.<\/span><\/p>\n

Thermal bypass meters are more advantageous for higher flow rates because it lowers the energy that would be required to heat the entire flow path. Within a bypass flow meter, most of the fluid travels through the main flow path with laminar plates, while a small, but proportional amount of fluid is pushed into a bypass tube. The temperature change measured in the bypass tube is used to calculate information about the entire flow rate. The laminar flow elements are key to maintaining accuracy, but also make the device more difficult and expensive to build.<\/span><\/p>[\/et_pb_text][\/et_pb_column][et_pb_column type=”2_5″ _builder_version=”4.25.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/www.alicat.com\/wp-content\/uploads\/2026\/01\/mems-measurement-explainer-split.webp” title_text=”measurement explainer mems ” align=”right” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”|||8px||” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_image][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”0px||||false|false” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.25.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.25.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]

How do MEMS thermal flow sensors work?<\/h2>\n

Thermal mass flow meters most commonly use MEMS sensors<\/a> \u2013 small sensors which can measure one of a variety of physical states, including temperature. MEMS flow sensors are also referred to as CMOS (complementary metal-oxide-semiconductor) flow sensors. There are two main types of MEMS flow sensors: anemometric sensors, and calorimetric sensors.<\/span>\u00a0<\/span><\/p>\n

Anemometric Sensors<\/h3>\n

MEMS anemometric sensors measure mass flow rates by measuring the energy dissipation of a gas through the heating element. Since the resistance of the heating element is dependent on its temperature, gas flowing past the heater will cool it down and decrease this resistance.<\/span>\u00a0<\/span><\/p>\n

Calorimetric Sensors<\/h3>\n

MEMS calorimetric sensors measure mass flow rates with symmetrical thermopiles upstream and downstream of the heating element. Power is provided to the heating element to keep the temperature differential constant. When there is no flow, the sensors read the same value. When gas is flowing, the heated gas travels downstream, and the downstream sensor will be hotter than the upstream sensor.<\/span>\u00a0<\/span><\/p>[\/et_pb_text][et_pb_image src=”https:\/\/www.alicat.com\/wp-content\/uploads\/2024\/04\/thermal-chipflow-temperature-distribution-768×264-1.webp” title_text=”thermal-chipflow-temperature-distribution-768×264″ align=”center” _builder_version=”4.27.4″ _module_preset=”default” custom_margin=”2rem||2rem||true|false” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_image][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]

\n\n,\n

MEMS calorimetric sensors measure the temperature differential between two sensors.<\/p>\n\n<\/div>\nThe expression below outlines the relationship between the temperature differential, mass flow, and other variables.<\/span>\n\n<\/span>\n

\n

Temperature Lost<\/h3>\n
\n
\n\n\n\n
\n

\u0394T \u221d K \/ qm<\/sub> \u00d7 Cp<\/sub><\/strong><\/em><\/h2>\n
\n
\n\n\u0394T<\/strong><\/em>: temperature differential\u00a0<\/span>\n\nK<\/strong><\/em>: meter coefficient\u00a0<\/span>\n\n<\/div>\n<\/div>\n
\n
\n

qm<\/sub><\/strong><\/em>: mass flow rate\u00a0<\/span><\/p>\n

Cp<\/sub><\/strong><\/em>: thermal capacitance\u00a0<\/span><\/p>\n\n<\/div>\n<\/div><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/span>\n\nThe meter coefficient, K<\/em><\/strong>, is dependent on the power consumed by the heater as well as the thermal conductivity of the fluid. As the flow rate increases, the heater consumes more power as it keeps the temperature differential constant. Using the above equation, the mass flow rate can be calculated.<\/span>\u00a0<\/span>\n\n<\/div>\n<\/div>\n<\/div>\n

<\/span><\/b><\/h2>\n

Advantages<\/span>\u00a0of MEMS Thermal Flow Measurement<\/span><\/h2>\n
    \n\t
  1. Light weight and inexpensive \u2013 MEMS thermal flow sensors have a simple internal structure.<\/span><\/li>\n\t
  2. Minimal drift over time and therefore require less frequent calibration than some other types of flow sensors.<\/span>\u00a0<\/span><\/li>\n<\/ol>\n

    <\/h2>\n

    Disadvantages of MEMS Thermal Flow Measurement<\/h2>\n
      \n\t
    1. Typically cannot reach the accuracy achieved by laminar differential pressure (DP) mass flow sensors<\/span><\/a>\u00a0or\u00a0<\/span>Coriolis flow sensors,<\/span><\/a> or thermal bypass.<\/li>\n\t
    2. Gas composition must be known.\u00a0<\/span><\/li>\n\t
    3. Warm-up time is longer than laminar DP and Coriolis instruments but shorter than Thermal Bypass. The heating element can take several minutes to heat up and achieve specified accuracy.<\/span>\u00a0<\/span><\/li>\n<\/ol>[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”2_3,1_3″ use_custom_gutter=”on” gutter_width=”4″ _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”0px||||false|false” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”2_3″ _builder_version=”4.25.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” hover_enabled=”0″ global_colors_info=”{}” theme_builder_area=”post_content” sticky_enabled=”0″]

      Products<\/span><\/b><\/h2>\nAlicat\u2019s\u00a0<\/span>BASIS 2 <\/span>MEMS thermal mass flow meters<\/a> and controllers<\/a> use a calorimetric MEMS thermal sensor positioned directly in the flow path. These powerful, premier devices offer high accuracy on a list of gases (that can be changed by the user) and have a small footprint. These devices are commonly used to upgrade from rotameters and manual control valves in a variety of applications, including gas chromatography, bioreactor sparging, and furnace control. BASIS 2 controllers are also available in a manifold configuration<\/a> for gas mixing.<\/span>[\/et_pb_text][\/et_pb_column][et_pb_column type=”1_3″ _builder_version=”4.25.1″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/www.alicat.com\/wp-content\/uploads\/2024\/05\/BASIS2_Pair.webp” alt=”Small MEMS thermal BASIS mass flow meters and controllers from Alicat for small footprints.” title_text=”BASIS_AlicatScientific” align=”center” _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_image][\/et_pb_column][\/et_pb_row][\/et_pb_section]\n","protected":false},"featured_media":46458,"parent":0,"template":"","meta":{"_acf_changed":false,"_et_pb_use_builder":"on","_et_pb_old_content":"","_et_gb_content_width":"","content-type":"","_searchwp_excluded":""},"categories":[],"class_list":["post-40901","support","type-support","status-publish","has-post-thumbnail","hentry"],"acf":[],"yoast_head":"\nThermal Flow Meter \u2013 Operating Principle\u00a0 - Alicat Scientific<\/title>\n<meta name=\"description\" content=\"Learn more about thermal flow metering and the operation principles behind MEMS thermal mass flow technology, which is used in BASIS meters and controllers.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.alicat.com\/de\/unterstutzung\/mems-thermisches-massenstrommessgerat-arbeitsprinzip\/\" \/>\n<meta property=\"og:locale\" content=\"de_DE\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Thermal Flow Meter \u2013 Operating Principle\u00a0\" \/>\n<meta property=\"og:description\" content=\"Learn more about thermal flow metering and the operation principles behind MEMS thermal mass flow technology, which is used in BASIS meters and controllers.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.alicat.com\/de\/unterstutzung\/mems-thermisches-massenstrommessgerat-arbeitsprinzip\/\" \/>\n<meta property=\"og:site_name\" content=\"Alicat Scientific\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/alicatscientific\/\" \/>\n<meta property=\"article:modified_time\" content=\"2026-01-23T18:12:00+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.alicat.com\/wp-content\/uploads\/2026\/01\/featured-alicat.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1200\" \/>\n\t<meta property=\"og:image:height\" content=\"630\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"4\u00a0Minuten\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.alicat.com\\\/support\\\/mems-thermal-mass-flow-meter-operating-principle\\\/\",\"url\":\"https:\\\/\\\/www.alicat.com\\\/support\\\/mems-thermal-mass-flow-meter-operating-principle\\\/\",\"name\":\"Thermal Flow Meter \u2013 Operating Principle\u00a0 - 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