Field service engineers require a variety of load cells spanning the various ranges needed to calibrate their customers’ systems. They may also require the assortment to conduct an array of force measurements for the testing application. The process begins when the engineer has to modify the load cell which is connected to his instrument before he can continue. When the new cell is linked to the instrument, the appropriate calibration factors have to be installed in the Force Sensor.
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 lead to erroneous results and costly recalibration expenses. Instrumentation that automatically identifies the load cell being mounted on it and self-installing the correct calibration data 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 that include common, network-independent communication interfaces for connecting transducers to microprocessors and instrumentation systems.
With TEDS technology, data may be stored on the inside of a memory chip which is installed inside of a TEDS-compliant load cell. The TEDS standard is complicated. It specifies a huge number of detailed electronic data templates with a few amount of standardization. Even while using the data templates, it is not guaranteed that different vendors of TEDS-compliant systems will interpret what data is put into the electronic templates in a similar manner. More importantly, it is far from apparent that the calibration data that is needed in your application is going to be supported by a certain vendor’s TEDS unit. You need to also ensure that you have a way to write the TEDS data to the TEDS-compatible load cell, either through a TEDS-compatible instrument that 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 also need to be noted that calibration data that is saved in the burden cell is identical regardless of what instrument is attached to it. Additional compensation for your Torque Sensor is not included. Matched systems in which a field service calibration group might be attaching different load cells to different instruments can present an issue.
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 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 little and inexpensive electronic identification chip is positioned within the cable that extends from your load cell or it may be mounted within the cell housing. This chip contains a unique electronic serial number that can be read through the ESL Model 4215 or CellMite to identify the cell. The cell will be connected to the unit and a standard calibration procedure is carried out. The instrument automatically stores the calibration data in the unit itself together 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. Using this system the calibration data can automatically include compensation for your particular instrument to ensure 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 that it has stored internally for that 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 right into a TEDS-Tag cell. The electronic identification chip, Dallas Semiconductor part number DS2401, is readily available from distributors or from ESL. The chip is quite small, rendering it simple to squeeze 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 via a DB9 connector with identical pin outs. The electronic identification chip fails to affect the cell’s signals. Pin 3 of 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 using off-the-shelf load cells, it is often useful to locate the DS2401 inside the hood in the cable. The cell includes a permanently mounted cable that protrudes through the cell housing. After the cable, strip back the insulation through the individual wires and solder the wires to the DB9 connector. The DS2401 is soldered across DB9 pins 7 and 8, and fits in the connector’s hood. For a couple of dollars in parts and 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 where accessibility load cell and cable is restricted, an in-line tag identification module can be simply constructed. A straight through in-line cable adapter can incorporate the DS2401 electronic tag chip. Within this application, the cable adapter is in fact placed in series with the load cell cable before it really is plugged into the Load Cell. Additionally it is possible to utilize this technique in applications where different calibrations might be required on the same load cell. An individual may mbssap one particular load cell and instrument, but can 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 an alternative calibration data set with every in-line adapter. This might be useful, as an example, when a precision 6-point linearization in the load cell is needed in two different operating ranges of the same load cell.