Field service engineers require a variety of load cells spanning the numerous ranges required to calibrate their customers’ systems. They could also require the assortment to conduct an array of force measurements for a particular testing application. The challenge begins when the engineer must alter the load cell which is connected to his instrument before he is able to continue. If the new cell is connected to the instrument, the proper calibration factors need to be installed in the Load Cell.
Avoiding user-error is actually a major challenge with manual data entry or with requiring the engineer from which to choose a database of stored calibration parameters. Loading the incorrect parameters, or even worse, corrupting the current 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 correct calibration information 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 which include common, network-independent communication interfaces for connecting transducers to microprocessors and instrumentation systems.
With TEDS technology, data can be stored inside of a memory chip that is certainly installed inside of a TEDS-compliant load cell. The TEDS standard is complicated. It specifies a huge number of detailed electronic data templates with many degree of standardization. Even while 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. Moreover, it is not apparent that the calibration data that is needed inside your application is going to be supported by a specific vendor’s TEDS unit. You must also ensure that you have a means to write the TEDS data in 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, including calibration systems, it should also be noted that calibration data that is stored in the burden cell is the same whatever instrument is attached to it. Additional compensation for your Torque Transducer is not included. Matched systems when a field service calibration group may be attaching different load cells to different instruments can present an issue.
Electro Standards Laboratories (ESL) has created the TEDS-Tag auto identification system which retains the attractive feature of self identification found in the TEDS standard but may be implemented simply on any load cell and, when linked to the ESL Model 4215 smart meter or CellMite intelligent digital signal conditioner, becomes transparent to the user. Multiple load-cell and multiple instrument matched pair calibrations will also be supported. This can be a critical advantage in precision applications like field calibration services.
With the TEDS-Tag system, a little and inexpensive electronic identification chip is put inside the cable that extends through the load cell or it can be mounted within the cell housing. This chip has a unique electronic serial number that may be read from the ESL Model 4215 or CellMite to identify the cell. The cell will be linked to the unit and a standard calibration procedure is conducted. 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 to 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 so that high precision matched systems may be realized. Moreover, in the event the cell is transferred to another instrument, that instrument will recall the calibration data which it has stored internally for the load cell. The ESL instruments can store multiple load cell calibration entries. In this way, multiple load cells can form a matched calibration set with multiple instruments.
Any load cell can be easily 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 extremely small, which makes it easy to match a cable hood or cell housing.
The ESL Model 4215 smart strain gauge indicator and also the CellMite intelligent digital signal conditioner are attached to load cells via a DB9 connector with identical pin outs. The electronic identification chip fails to hinder the cell’s signals. Pin 3 of the DS2401 is not used and can be stop if desired. Simply connecting pins 1 and 2 through the DS2401 to pins 8 and 7, respectively, in the ESL DB9 connector will enable plug-and-play operation.
When utilizing off-the-shelf load cells, it is usually useful to locate the DS2401 inside 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 from the individual wires and solder the wires to the DB9 connector. The DS2401 is soldered across DB9 pins 7 and 8, and fits inside the connector’s hood. For a couple dollars in parts along with a simple cable termination procedure, you may have taken a typical load cell and transformed it into a TEDS-Tag plug-and-play unit.
For applications by which access to the load cell and cable is fixed, 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 put into series using the load cell cable before it is connected to the Weight Sensor. It is additionally possible to make use of this technique in applications where different calibrations could be required on the same load cell. The user may mbssap just one load cell and instrument, but can change which calibration is auto-selected by just changing the in-line cable adapter. Since each cable adapter has a different tag identification chip, the ESL instrument will associate another calibration data set with each in-line adapter. This can be useful, for instance, in case a precision 6-point linearization in the load cell is needed in 2 different operating ranges of the same load cell.