Field service engineers require a number of load cells spanning the numerous ranges necessary to calibrate their customers’ systems. They could also require the assortment to conduct an array of force measurements for the testing application. The task begins once the engineer needs to modify the load cell which is attached to his instrument before he can continue. Once the new cell is attached to the instrument, the correct calibration factors have to be set up in the Force Transducer.
Avoiding user-error is really a major challenge with manual data entry or with requiring the engineer to select from a database of stored calibration parameters. Loading the incorrect parameters, as well as worse, corrupting the present calibration data, can result in erroneous results and costly recalibration expenses. Instrumentation that automatically identifies the burden cell being mounted on it and self-installing the appropriate calibration data is optimal.
What 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 that include common, network-independent communication interfaces for connecting transducers to microprocessors and instrumentation systems.
With TEDS technology, data may be stored within a memory chip that is installed within a TEDS-compliant load cell. The TEDS standard is complicated. It specifies a large number of detailed electronic data templates with many degree of standardization. Even while using the data templates, it is far from guaranteed that different vendors of TEDS-compliant systems will interpret what data goes into the electronic templates in the same way. More importantly, it is not apparent that this calibration data that is required inside your application will be supported by a specific vendor’s TEDS unit. You must also make certain you have a means to write the TEDS data into the TEDS-compatible load cell, through either a TEDS-compatible instrument which has both TEDS-write and TEDS-read capabilities, or with the use of a few other, likely computer based, TEDS data writing system.
For precision applications, like calibration systems, it should also be noted that calibration data which is saved in the stress cell is identical whatever instrument is attached to it. Additional compensation for that Torque Transducer is not included. Matched systems in which a field service calibration group may be attaching different load cells to different instruments can present an issue.
Electro Standards Laboratories (ESL) has evolved the TEDS-Tag auto identification system which retains the attractive feature of self identification located in the TEDS standard but may be implemented simply on any load cell and, when connected 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 is often a critical advantage in precision applications like field calibration services.
With the TEDS-Tag system, a little and inexpensive electronic identification chip is put within the cable that extends from the load cell or it may be mounted inside the cell housing. This chip contains a unique electronic serial number that may be read through the ESL Model 4215 or CellMite to recognize the cell. The cell will then be linked to the unit along with a standard calibration procedure is carried out. The instrument automatically stores the calibration data inside the unit itself along with the unique load cell identification number through the microchip. Whenever that cell is reconnected for the instrument, it automatically recognizes the cell and self-installs the proper calibration data. True plug-and-play operation is achieved. With this system the calibration data can automatically include compensation for your particular instrument so that high precision matched systems may be realized. Moreover, if the cell is moved to another instrument, that instrument will recall the calibration data that it has stored internally for your 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 in to a TEDS-Tag cell. The electronic identification chip, Dallas Semiconductor part number DS2401, is readily provided by distributors or from ESL. The chip is quite small, rendering it very easy to fit into 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 via a DB9 connector with identical pin outs. The electronic identification chip will not hinder the cell’s signals. Pin 3 of the DS2401 is not really used and will be stop if desired. Simply connecting pins 1 and two through the DS2401 to pins 8 and 7, respectively, of the ESL DB9 connector will enable plug-and-play operation.
When utilizing off-the-shelf load cells, it is usually easy to locate the DS2401 within the hood in the cable. The cell features a permanently mounted cable that protrudes through the cell housing. After the cable, strip back the insulation from your individual wires and solder the wires into the DB9 connector. The DS2401 is soldered across DB9 pins 7 and 8, and fits in the connector’s hood. For a few dollars in parts along with a simple cable termination procedure, you might have taken a standard load cell and transformed it right into a TEDS-Tag plug-and-play unit.
For applications where access to the 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. In this particular application, the cable adapter is actually placed in series with the load cell cable before it is connected to the Load Cell. It is also easy to make use of this technique in applications where different calibrations could be required on the same load cell. An individual may mbssap a single load cell and instrument, but may change which calibration is auto-selected by simply changing the in-line cable adapter. Since each cable adapter features a different tag identification chip, the ESL instrument will associate another calibration data set with every in-line adapter. This might be useful, for instance, in case a precision 6-point linearization in the load cell is required by two different operating ranges of the same load cell.