Measuring devices of the aforementioned type are used in the automation technology for monitoring the properties of a fluid, for example in terms of pressure, temperature, flow rate, level, wherein a cylindrical sensor tip is provided most often in thermometers and thermal flow meters. In such measuring devices a temperature sensitive electronic component, which senses the temperature of a medium surrounding the sensor tip, is located in the sensor tip. As one example a Pt100 element can be mentioned. In order to enable that the temperature is transmitted almost without loss to the temperature sensitive component it is soldered to the inside of the housing wall of the sensor tip. A thermally conductive, but electrically insulating layer which is disposed between the temperature sensitive component and the solder, ensures the almost loss-free transmission of the temperature to this component, however, it isolates the component from the housing of the sensor tip. Such a configuration is shown, for example, in EP 0 590 449 A2.
For the thermal and, thus, metrological characteristics of such measuring devices comprising components soldered in the sensor tip the soldering process, in which the component in question is connected to the inner bottom of a housing consisting e.g. of stainless steel, is critical. Non-controllable fluctuations during the soldering process can lead to significant variations in the characteristics of a sensor series. In particular with flow meters in addition to the amount also the homogeneity and geometric distribution of the solder is critical for a qualitatively constant production of the sensor tips and their metrological characteristics. This can inter alia be crucial in determining whether the measuring devices subsequently have to be calibrated individually or not.
Thus, problematic is on the one side the soldering process itself, since the diameter of the sensor tip is usually in the range 5-10 mm and, thus, a soldering process in a conventional manner is not possible. On the other side, a constant solder distribution and a uniformly thick layer of solder must be ensured in order to keep the dispersion of the characteristics of the measuring device as small as possible and to reduce the calibration effort of manufactured measuring devices.
In this regard DE 10 2006 048 448 A1 proposes to apply a predetermined amount of solder onto the component and to approach the component to the inside of the sensor tip such that the solder is located between the component and the inside of the sensor tip, and subsequently to melt the solder. However, herein a disadvantage is the comparatively high expenditure, in particular with respect to the necessary overhead soldering process and that a displacement mechanism has to be provided in order to realize the defined approach of the component.
USPTO Backgrounds
USPTO Backgrounds