Measuring and testing – Dynamometers – Responsive to force
Patent
1998-05-15
2000-07-04
Fuller, Benjamin R.
Measuring and testing
Dynamometers
Responsive to force
G01L 104
Patent
active
060822031
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a sensing element for measuring loads according to the introductory section of the independent patent claim.
In the prior art there is known a measuring arrangement where a sensing element, particularly a strain gauge transducer, is directly attached to the structure of the target under measurement by adhesion. A drawback in this arrangement is that the base where the sensor is attached must be well cleaned, and the adhesion must be performed with care. Otherwise there is the risk that the sensor may at some stage suddenly detach from the base. The fastening must be carried out the more carefully, the more demanding is the environment where the sensor is fitted. A particularly difficult environment is the frame structure of a vehicle when measuring the strains, particularly load strains, directed thereto. The temperature around the vehicle may vary for instance from +30.degree. C. to -40.degree. C. Moreover, the sensor is subject to continuous shaking while the vehicle moves. At times the sensor may also be subject to powerful impacts in the form of stones or the like flown off the road surface; such impacts the sensor does not endure but is broken.
In the prior art there is known a measuring arrangement where a sensing element, particularly a strain gauge transducer, is directly attached to the structure under measurement by adhesion, and in the vicinity of this or several sensors, at a slight distance, there is placed a measuring transmitter or the like in order to process the analog measuring signal obtained from the sensor/sensors, for instance in order to amplify the signal and convert it to a current message or a digital message, and further in order to transmit it to the data collecting and processing unit, wherefrom the strain values, such as weight strain, directed to the structures are announced.
A drawback in arranging the sensor/sensors and the measuring transmitter at a distance from each other is that within said interval, interference is summed in the measuring message, and the noise level grows.
The object of the present invention is to introduce a novel sensing element for measuring strains directed to a structure, whereby at least part of the above described drawbacks can be avoided.
The sensing element according to the invention is characterised by the novel features enlisted in the independent patent claim.
The structure of the sensing element according to the invention for measuring loads comprises: a strain transducer unit measuring structural strain, including a strain transducer element, such as a strain gauge element; and a protecting shell, inside which the strain transducer unit is arranged and which comprises: a base plate, on top of which the strain transducer unit is attached; and a protecting hood, which is fitted around the strain transducer unit, on top of the base plate.
An advantage of the invention is that the strain transducer unit is effectively protected by means of the protecting shell. Another advantage is that when the base plate and the protecting hood are made of metal sheet, advantageously steel sheet, the sensor is easily attached to a metal structure, particularly a steel beam, by welding at the base plate. Thus the fastening of the sensors to the target under measurement is carried out more rapidly, and it does not require so extensive and careful preparations as in a case where the strain gauge element alone is glued to the base. A further advantage of the invention is that the strain transducer unit fitted inside the protecting shell is easily tested in a test bench prior to the installation proper, and thus the operation of the strain transducer unit can be checked. It is yet an advantage of the invention that the sensor is replaceable on the measuring site in a fairly simple fashion in case of malfunction for one reason or another.
According to a preferred embodiment of the invention, the strain transducer unit comprises an A/D converter and a microprocessor for converting the analog measuring message to digital form and for pretr
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Koivisto, Marja-Liisa; Official Action; Apr. 21, 1998.
Koivisto, Marja-Liisa; Official Action; May 14, 1996.
Koivisto Vesa
Sundqvist Jari
Fuller Benjamin R.
Marja-Liisa Koivisto
Thompson Jewel
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