Unidirectional Pressure Transducers
Unidirectional pressure transducers measure between zero and a positive pressure. The diaphragm of the sensor should only move in one direction and will produce a positive voltage or milliamp output.
Unidirectional transducers are used in a large variety of HVAC applications such as monitoring static duct pressure; the high port is connected to the point in the duct being monitored. Another example of this would be measuring the differential pressure across a filter to determine whether or not that filter needs to be replaced. In this case, the high port is connected to the inlet side of the filter and the low port is connected to the discharge side.
These kind of transducersare used in applications where the direction of flow is known and is not expected to change. If the flow of air reverses, the transducer will be out of range of what it can monitor.
Bidirectional Pressure Transducers
The diaphragm of a bidirectional pressure transducer can move in two different directions, enabling the sensor to measure both positive and negative pressure.
Bidirectional transducers are often used in room pressurization applications.Hospital operatingrooms, isolation rooms, pharmacies, vivariums, and other critical environments需要保持两个方向的压差，以维持病人的健康或以其他方式保持区域不受污染。正压区域将外部污染物挡在外面，负压区域将内部污染物挡在里面。在任何一种情况下，在安装过程中，换能器的高端口总是连接到被控制的房间，低端口连接到外部参考，如相邻的走廊。
SETRA BLOG:How employees can contaminate a clean environment.
NOTE:It is important that the range of the sensor is wide enough for the total amount of pressure the sensor is expected to encounter. It is very important that the sensor is NOT exposed to pressures above its listed range. Setra sensors are rated for their stated ranges and exposing the sensors to excessive overpressure will degrade the accuracy of the unit.
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