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PRT vs Calorimetric Differential Pressure Technology

Mitsumi designed and developed two distinctly different technologies for differential pressure measurement technique. In order to reach a wide range of customers, it was important to introduce two types of DP sensors to the market: dead-end type and flow-through-type. We offer both the MEMS Piezoresistive (dead-end) and MEMS Calorimetric (thermal flow-through) sensing technologies.  Both technologies are limited to gas pressure measurement only (no liquid).

MEMS PRT Differential Pressure Sensor

The MMR94X series PRT differential pressure sensor utilizes our gauge pressure sensor with an additional plastic housing and PCB to deliver a cost effective, high performance DP sensor. The MMR94x directly measures the actual pressure difference between each side of the PRT die and does not require air to flow through the sensor.

Since there is no gas flow through the sensor, inlet restrictions within the pressure ports can be incorporated to deter water ingress into the sensor. Water ingress protection is not possible for flow based differential pressure sensors since a tight restriction would increase flow impedance thereby reducing sensor sensitivity and range. Testing has show that both ports on the MMR94x can withstand low pressure water ingress. This feature is important for applications such as CPAP where tipping of the device can lead to sensor damage from water intrusion.

For applications where the pressure media may be contaminated with particles such as dust, lint, rust flakes and high humidity, we recommend our MEMS piezoresistive differential pressure sensor. MEMS PRT technology requires no air flow to pass over the sensing element thus it is highly resistance to pressure media contamination and impervious to signal losses from long tubing lengths.  Additionally, MEMS PRT is not impacted by changes in barometric pressure because its measurement technique is independent of the pressure media density and there is no need for altitude correction.

Calorimetric (Thermal Flow) Technology

For applications where clean dry air is the pressure media and high resolution and sensitivity are required, we recommend the Mitsumi MEMS Calorimetric (thermal flow) differential pressure sensor. This technology offers excellent zero accuracy and stability since the sensing element is not impacted by changes in packaging distortion caused by environmental stress.

The MMS60X series sensor utilizes MEMS thermal technology for differential pressure measurement. At the heart of the sensor is a thermal flow chip containing a heater sandwiched by two equally spaced thermopiles. With the absence of gas flow, the thermopiles absorb roughly the same amount of heat, and the temperature difference between the two thermopiles is negligible. As gas flow increases, convection forces the downstream thermopile to receive more heat and a difference in temperature between the upstream and downstream thermopiles can be correlated to flow or differential pressure.

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