Measuring device with evaluation unit and external memory

#Apparatuses consistent with the present invention relate to a measuring device, and more particularly to a measuring device having a replaceable sensor with a permanently connected signal cable and a connector at the cable end for transmitting a sensor signal. The measuring device further includes a non-volatile electronic data memory for holding sensor-specific calibration data, and an evaluation unit with a port for connecting the signal cable. The sensor signal is evaluated in the evaluation unit using the calibration data.

#In measuring devices with replaceable sensors, the respective sensor can be easily decoupled from the evaluation unit by a pin-and-socket connector. In case of a defect, which occurs most often on the sensor, but may also occur in the evaluation unit, these components can be easily decoupled and replaced by an intact component to perform a repair. When different sensors with different metrological characteristics, such as different measured quantities or measurement ranges, are used, the sensors can be replaced while using the same evaluation unit. In this case, the evaluation unit is adapted to the changed metrological characteristics of the sensor by corresponding settings. The drawback in measuring devices of this type, however, is that after every replacement of a component, particularly a sensor, the entire measuring device must be recalibrated and the result stored in the form of calibration data, usually in a data memory of the evaluation unit or a personal computer connected downstream. This is not only very time consuming and expensive but has also the drawback that the respective sensor is not safely linked to the associated calibration data. This may lead to mistakes or even the loss of calibration data regarding the sensor.

#To assign identification data to a sensor of a measuring device, a data plate with a readable code is typically mounted to the sensor itself or to a component permanently connected to the sensor, such as a connection cable. For example, the German Laid Open Publication DE 37 09 717 A1 and the German Utility Model DE 83 21 954 U1 each disclose a balance (measuring device) comprising a load cell (sensor) with a permanently connected signal cable and a connector at the cable end, a display unit with an indicator field (display), and a port to connect the signal cable. A data plate with readable metrological characteristics, such as the measuring range of the load cell, information as to the date of the last official calibration, and the validity of the calibration, is inseparably fixed to the signal cable, such that the data plate is in the immediate proximity of the display of the evaluation unit when the load cell is connected and the metrological characteristics can be read as required. The drawback is that this does not ensure a reliable assignment of the respective calibration data to a given replaceable load cell. A further drawback is that a manufacturer-specific connection is required, so that it is not possible to use sensors from just any manufacturer.

#Further details of the invention will now be described by way of example, with reference to the exemplary embodiments of the measuring device according to the invention depicted in the drawings, in which:

#FIG. 1 is a three-dimensional representation of a first embodiment of a measuring device according to the invention,

#FIG. 2 is a three-dimensional representation of a fastening element with a memory cable,

#A measuring device 1 as illustrated in FIG. 1 has a sensor 2 and an evaluation unit 3 as its main components. To transmit a sensor signal, the sensor 2, which in this case is a pH electrode 4, has a permanently connected signal cable 5 and a connector 6 at the cable end (see FIG. 4) and is thus replaceable in relation to the evaluation unit 3. On the backside 7, the evaluation unit 3 has a port 8 for connecting the signal cable 5 or the connector 6. The sensor 2 is assigned a non-volatile electronic data memory 9, preferably an EPROM or EEPROM, in which the sensor-specific calibration data of the sensor 2, which are required for evaluating the sensor signal, are stored. According to the invention, the data memory 9 is permanently enclosed in a separate memory housing 10, which is configured as a receptacle of a fastening element 11 and encloses the data memory 9. With the fastening element 11 the memory housing 10 is spaced apart from, and inseparably fixed to, the signal cable 5. To transmit the calibration data to the evaluation unit 3, the data memory 9 is connected to the evaluation unit 3 via a separate data transmission channel 12, which in this case is a cable connection 13. The cable connection 13 includes a memory cable 14 permanently connected to the data memory 9 with a connector 15 at the end of the cable (see FIG. 2) and a port 22 disposed on the backside 7 of the evaluation unit 3.

#The fastening element 11 is configured as a permanently lockable holding clip 16 with at least one locking projection 10a and an associated locking recess 10b. In this case, the holding clip 16 is integrally connected to the memory housing 10, such that a first part of the memory housing 10 together with a first part of the holding clip 16 communicates with a second part of the memory housing 10 and a second part of the holding clip 16 via a bending hinge 17. The holding clip 16 can be permanently interlocked with the memory housing 10 in a single work step by swinging the two parts together.

#As shown in FIG. 5, the fastening element 11′ or the holding clip 16′ can also be inseparably fixed to the cable connector 6. The fastening element 11′ can then be connected to the evaluation unit by its own connectors.