Field service engineers require many different load cells spanning the numerous ranges necessary to calibrate their customers’ systems. They may also require the assortment to conduct a wide range of force measurements for a particular testing application. The challenge begins when the engineer has to modify the load cell which is linked to his instrument before he can continue. When the 3 axis load cell is attached to the instrument, the appropriate calibration factors have to be set up in the instrument.
Avoiding user-error is actually a major challenge with manual data entry or with requiring the engineer to select from a database of stored calibration parameters. Loading a bad parameters, or even worse, corrupting the existing calibration data, can cause erroneous results and costly recalibration expenses. Instrumentation that automatically identifies the burden cell being mounted on 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 inside of a memory chip which is installed within a TEDS-compliant load cell. The TEDS standard is complicated. It specifies a huge number of detailed electronic data templates with a few degree of standardization. Even when using the data templates, it is really not guaranteed that different vendors of TEDS-compliant systems will interpret what data is put into the electronic templates in the same way. More importantly, it is not apparent that this calibration data that is required in your application is going to be backed up by a particular vendor’s TEDS unit. You need to also make certain you have a method to write the TEDS data to the TEDS-compatible load cell, through a TEDS-compatible instrument which includes both TEDS-write and TEDS-read capabilities, or by using various 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 burden cell is identical no matter what instrument is linked to it. Additional compensation for your instrument is not included. Matched systems where a field service calibration group could be attaching different load cells to different instruments can present a difficulty.
Electro Standards Laboratories (ESL) has developed the TEDS-Tag auto identification system which retains the attractive feature of self identification located in the TEDS standard but can 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 such as field calibration services.
With all the TEDS-Tag system, a small and cheap electronic identification chip is placed inside the cable that extends through the load cell or it can be mounted inside the cell housing. This chip includes a unique electronic serial number that may be read from the ESL Model 4215 or CellMite to distinguish the cell. The cell will then be connected to the unit and a standard calibration procedure is conducted. The instrument automatically stores the calibration data inside the unit itself combined with the load sensor identification number from your microchip. Whenever that cell is reconnected to the instrument, it automatically recognizes the cell and self-installs the correct calibration data. True plug-and-play operation is achieved. With this particular system the calibration data can automatically include compensation for the particular instrument so that high precision matched systems can be realized. Moreover, when the cell is moved to another instrument, that instrument will recall the calibration data which it has stored internally for your load cell. The ESL instruments can store multiple load cell calibration entries. This way, 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 easily offered by distributors or from ESL. The chip is very small, rendering it simple to fit into a cable hood or cell housing.
Both the 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 will not hinder the cell’s signals. Pin 3 in the DS2401 is not really used and can be shut down if desired. Simply connecting pins 1 and two from your 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 often convenient to locate the DS2401 within the hood from the cable. The cell features a permanently mounted cable that protrudes through the cell housing. At the conclusion 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 and a simple cable termination procedure, you might have taken a typical load cell and transformed it in to a TEDS-Tag plug-and-play unit.
For applications by which accessibility load cell and cable is restricted, an in-line tag identification module may 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 really placed in series with the load cell cable before it really is connected to the ESL instrument. Additionally it is possible to utilize this technique in applications where different calibrations could be required on the same load cell. The ifegti could have a single load cell and instrument, but can change which calibration is auto-selected by simply changing the in-line cable adapter. Since each cable adapter includes a different tag identification chip, the ESL instrument will associate another calibration data set with every in-line adapter. This can be useful, for instance, if a precision 6-point linearization from the load cell is needed in 2 different operating ranges the exact same load cell.
Now that the load cell continues to be converted to a TEDS-Tag unit, it can be connected to the ESL Model 4215 smart strain gauge indicator or a CellMite intelligent digital signal conditioner. The 1st time that it is connected, a standard calibration procedure is conducted to initialize the cell’s calibration data in the instrument. The ESL instruments support many different industry standard calibrations including mV/V, shunt, 2-point, or multiple-point calibration. The instrument then automatically detects the actual existence of the force transducer and matches it using its calibration data. From this point forward, the system is totally plug-and-play.