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Non-invasive pressure sensing system Disclosure Number: IPCOM000180517D
Publication Date: 2009-Mar-11
Document File: 4 page(s) / 496K

Publishing Venue

The Prior Art Database


A non-invasive pressure sensing system is provided. The non-invasive pressure-sensing system comprises a spring, a potentiometer coupled to the spring and a MOSFET in operative association with the potentiometer. A pressure variation is sensed based on a change in the resistance of the potentiometer.

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The invention generally relates to a fetal monitoring device/apparatus, and more particularly to a non-invasive apparatus for sensing uterine activity, in particular, uterine contractions.


Fetal Monitors are typically quite sophisticated and are widely used to monitor the uterine activity of pregnant women, as well as condition of the fetus and uterus. Analysis of uterine contractions, in conjunction with fetal heart rate, during pregnancy and labor provide significant fetal related information relating to early signs of hypoxia, condition of the fetus and advancement of labor.  Information relating to stress on the fetus or early signs of hypoxia need prompt remedial action including cesarean delivery both during pregnancy and also during actual labor. On the other hand, early contractions can be treated to achieve full term pregnancies.

A device or sensor or transducer needs to be interfaced with the Fetal Monitor to actually sense the uterine contractions. The sensor/transducer may be intra uterine (invasive using catheter) or extra uterine (non invasive technique for measuring uterine contraction).

Prior art systems generally comprise a transducer/sensor used to detect uterine contractions based on the Linear Variable Differential Transformer (LVDT) principle. The diaphragm displacement (caused by the application of external load/pressure) is transferred to a button mounted on the LVDT. Following which, the button along with a ferrite core (press fitted with loctite inside the button) moves with respect to the LVDT causing a corresponding voltage change. This change in voltage is subsequently converted into an equivalent UA (Uterine Activity) reading.

However, the LVDT is associated with several disadvantages such as considerably high part count size to build the transducer. This in turn leads to increase in the level of complexity in manufacturing parts thereby requiring high level of skill dependency during final assembly. This results in considerable increase in the process time to build the Toco transducer.

Some of the other prior art pressure measurement devices are based on strain gauge or capacitive variations for example.

Accordingly, it is desirable to develop a device/sensor/transducer for measuring uterine contractions which is inexpensive, easy to operate and maintain, simple...