Field service engineers require a variety of load cells spanning the different ranges necessary to calibrate their customers’ systems. They might also require the assortment to conduct a variety of force measurements for the testing application. The challenge begins once the engineer needs to modify the load cell that is linked to his instrument before he can continue. Once the new cell is attached to the instrument, the appropriate calibration factors must be installed in the Force Sensor.
Avoiding user-error is really a major challenge with manual data entry or with requiring the engineer from which to choose a database of stored calibration parameters. Loading a bad parameters, or even worse, corrupting the present calibration data, can result in erroneous results and costly recalibration expenses. Instrumentation that automatically identifies the burden cell being connected to it and self-installing the appropriate calibration information is optimal.
What exactly is Transducer Electronic Datasheet? A Transducer Electronic Data Sheet (TEDS) stores transducer identification, calibration and correction data, and manufacturer-related information in a uniform manner. The IEEE Instrumentation and Measurement Society’s Sensor Technology Technical Committee developed the formats which include common, network-independent communication interfaces for connecting transducers to microprocessors and instrumentation systems.
With TEDS technology, data could be stored within a memory chip that is installed on the inside of a TEDS-compliant load cell. The TEDS standard is complicated. It specifies a huge number of detailed electronic data templates with some degree of standardization. Even when using the data templates, it is not guaranteed that different vendors of TEDS-compliant systems will interpret what data goes into the electronic templates in the same manner. More importantly, it is not apparent that the calibration data that is required in your application will likely be supported by a certain vendor’s TEDS unit. You have to also ensure that you have a means to write the TEDS data to the TEDS-compatible load cell, through a TEDS-compatible instrument that has both TEDS-write and TEDS-read capabilities, or through the use of some other, likely computer based, TEDS data writing system.
For precision applications, like calibration systems, it also need to be noted that calibration data which is stored in the load cell is identical no matter what instrument is linked to it. Additional compensation for your Torque Sensor itself is not included. Matched systems where a field service calibration group could be attaching different load cells to various instruments can present a problem.
Electro Standards Laboratories (ESL) has developed the TEDS-Tag auto identification system which retains the attractive feature of self identification based in the TEDS standard but can be implemented simply on any load cell and, when attached to the ESL Model 4215 smart meter or CellMite intelligent digital signal conditioner, becomes transparent towards the user. Multiple load-cell and multiple instrument matched pair calibrations can also be supported. This can be a critical advantage in precision applications like field calibration services.
With the TEDS-Tag system, a small and inexpensive electronic identification chip is placed inside the cable that extends through the load cell or it can be mounted in the cell housing. This chip has a unique electronic serial number that may be read from the ESL Model 4215 or CellMite to recognize the cell. The cell will be attached to the unit along with a standard calibration procedure is performed. The instrument automatically stores the calibration data within the unit itself combined with the unique load cell identification number from your microchip. Whenever that cell is reconnected towards the instrument, it automatically recognizes the cell and self-installs the proper calibration data. True plug-and-play operation is achieved. With this particular system the calibration data can automatically include compensation for that particular instrument in order that high precision matched systems may be realized. Moreover, in the event the cell is moved to another instrument, that instrument will recall the calibration data that it has stored internally for the load cell. The ESL instruments can store multiple load cell calibration entries. In this manner, multiple load cells can form a matched calibration set with multiple instruments.
Any load cell can be simply made right into a TEDS-Tag cell. The electronic identification chip, Dallas Semiconductor part number DS2401, is easily available from distributors or from ESL. The chip is extremely small, which makes it very easy to match a cable hood or cell housing.
Both ESL Model 4215 smart strain gauge indicator and also the CellMite intelligent digital signal conditioner are linked to load cells by way of a DB9 connector with identical pin outs. The electronic identification chip does not affect the cell’s signals. Pin 3 from the DS2401 will not be used and will be cut off if desired. Simply connecting pins 1 and 2 from your DS2401 to pins 8 and 7, respectively, in the ESL DB9 connector will enable plug-and-play operation.
When you use off-the-shelf load cells, it is often easy to locate the DS2401 within the hood of the cable. The cell includes a permanently mounted cable that protrudes through the cell housing. At the end of the cable, strip back the insulation through the individual wires and solder the wires in to the DB9 connector. The DS2401 is soldered across DB9 pins 7 and 8, and fits within the connector’s hood. For a couple of dollars in parts as well as a simple cable termination procedure, you have taken a regular load cell and transformed it right into a TEDS-Tag plug-and-play unit.
For applications by which accessibility load cell and cable is fixed, an in-line tag identification module could be simply constructed. A straight through in-line cable adapter can incorporate the DS2401 electronic tag chip. Within this application, the cable adapter is really positioned in series using the load cell cable before it is plugged into the Weight Sensor. Additionally it is possible to utilize this technique in applications where different calibrations could be required on the same load cell. The user may mbssap a single load cell and instrument, but can change which calibration is auto-selected simply by changing the in-line cable adapter. Since each cable adapter includes a different tag identification chip, the ESL instrument will associate a different calibration data set with each in-line adapter. This can be useful, for instance, when a precision 6-point linearization in the load cell is necessary in 2 different operating ranges the exact same load cell.