Field service engineers require many different load cells spanning the various ranges necessary to calibrate their customers’ systems. They might also require the assortment to conduct a wide range of force measurements for a particular testing application. The task begins when the engineer has to change the load cell which is connected to his instrument before he is able to continue. If the new cell is linked to the instrument, the proper calibration factors need to be placed in the Force Transducer.
Avoiding user-error is a major challenge with manual data entry or with requiring the engineer to pick from a database of stored calibration parameters. Loading a bad parameters, as well as worse, corrupting the present calibration data, can lead to erroneous results and costly recalibration expenses. Instrumentation that automatically identifies the burden 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 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 large number of detailed electronic data templates with some degree of standardization. Even when using the data templates, it is far from guaranteed that different vendors of TEDS-compliant systems will interpret what data enters into the electronic templates in a similar manner. More importantly, it is far from apparent that this calibration data that is required in your application will likely be maintained 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 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 kept in the load cell is identical regardless of what instrument is linked to it. Additional compensation for your Torque Transducer is not included. Matched systems when a field service calibration group could be attaching different load cells to various 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 located in the TEDS standard but could 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 put 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 which can be read from the ESL Model 4215 or CellMite to identify the cell. The cell will be attached to the unit and a standard calibration procedure is carried out. The instrument automatically stores the calibration data inside the unit itself combined with the unique load cell identification number from the 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. Using this system the calibration data can automatically include compensation for that particular instrument to ensure that high precision matched systems can be realized. Moreover, if the cell is transferred 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. 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 available from distributors or from ESL. The chip is quite small, which makes it very easy to match a cable hood or cell housing.
Both the ESL Model 4215 smart strain gauge indicator and also the CellMite intelligent digital signal conditioner are attached to load cells by way of a DB9 connector with identical pin outs. The electronic identification chip does not hinder the cell’s signals. Pin 3 of the DS2401 is not used and will be stop if desired. Simply connecting pins 1 and two through the DS2401 to pins 8 and 7, respectively, from the ESL DB9 connector will enable plug-and-play operation.
When utilizing off-the-shelf load cells, it is often easy to locate the DS2401 in the hood from the cable. The cell includes a permanently mounted cable that protrudes from the cell housing. At the conclusion of the cable, strip back the insulation from the individual wires and solder the wires into 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 as well as 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 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 put into series using the load cell cable before it really is connected to the Weight Sensor. Additionally it is easy to utilize this technique in applications where different calibrations might 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 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 might be useful, as an example, in case a precision 6-point linearization from the load cell is required in two different operating ranges of the same load cell.