1. Field of the Invention
The present invention relates to a pressure sensor for measuring the pressure of gas, liquid or the like.
2. Discussion of the Related Art
Heretofore, as described in Japanese unexamined, published patent application No. 2002-13998 for example, there have been known a pressure sensor having a pressure sensing element placed in a pressure chamber in which pressure transmission medium is sealed off, and another pressure sensor having a pressure sensing element placed in a pressure chamber which is constructed so that fluid to be measured is flown thereinto.
However, in the aforementioned known pressure sensors, a problem arises in that the access to the pressure sensing element or an electric circuit incorporated therein is not easy. That is, for the reason that the access to the pressure sensing element arranged in the pressure chamber is not easy, it has been unable to enhance the productivity of the pressure sensor, and it has also been not easy to reduce the manufacturing cost therefor substantially.
For example, the foregoing problem in the prior art is remarkable in a pressure sensor which is provided with a compensation circuit for compensating the measured signal of the pressure sensing element.
In the pressure sensor, it is sometimes the case that after assembling, the output value is measured with a reference pressure, a reference temperature and the like being applied thereon to calibrate the measured signal for example. It is also sometimes the case that compensation data which is to be set in the compensation circuit is calculated based on the measured output value and is then set in the compensation circuit.
However, it is also often the case that the setting of the compensation data in the compensation circuit is not easily carried out in the pressure sensor after the assembling thereof.
As one capable of obviating the foregoing problems, there has been also known another pressure sensor in which a communication terminal electrically connected to the compensation circuit is additionally provided besides terminals for electric power supply and output signal. In this pressure sensor, it is necessary to take measures for, e.g., electrically isolating the communication terminal upon completion of the setting of the compensation data in the compensation circuit.
Therefore, in the pressure sensor, it is necessary to provide the communication terminal, an electrical path leading to the communication terminal, and the like which are rarely needed in the state of ordinary use as noted above, and a disadvantage is experienced in respect of cost in particular. In addition, disadvantages are also experienced in respect of productivity because it is required to electrically isolate the communication terminal after the completion of the setting work of the compensation data.
Furthermore, in the pressure sensor arranging the pressure sensing element in the pressure chamber as described above, terminal pins or the like constituting a path for power supply to the pressure sensing element and another path for outputting the measured signal are occasionally arranged to protrude into the pressure chamber.
Thus, sealing capability has to be reliably secured between the terminal pins and a housing member constituting a main body of the pressure sensor. In the prior art pressure sensor, measures have been taken to fill a sealing substance such as silicon or the like between the terminal pins and the housing member.
Therefore, a sealing process for filling the sealing substance has been essential in the foregoing pressure sensor. This disadvantageously has made a bottleneck in enhancing the productivity and also has made a cause to retard the realization of a low cost.