Field service engineers require a variety of load cells spanning the numerous 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 challenge begins when the engineer has to modify the load cell which is connected to his instrument before he could continue. Once the new cell is connected to the instrument, the proper calibration factors must be placed in the Force Sensor.
Avoiding user-error is a major challenge with manual data entry or with requiring the engineer from which to choose a database of stored calibration parameters. Loading the wrong 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 attached to it and self-installing the correct calibration details are optimal.
Precisely 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 on the inside of a memory chip that 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 amount of standardization. Even when using the data templates, it is not guaranteed that different vendors of TEDS-compliant systems will interpret what data enters into the electronic templates in a similar manner. Most importantly, it is really not apparent that the calibration data that is required inside your application will likely be backed up by a particular vendor’s TEDS unit. You have to also ensure that you have a way to write the TEDS data into the TEDS-compatible load cell, through either a TEDS-compatible instrument which includes 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 ought to be noted that calibration data that is stored in the load cell is the same no matter what instrument is attached to it. Additional compensation for your Torque Sensor is not included. Matched systems where a field service calibration group may be attaching different load cells to different instruments can present a difficulty.
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 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 to the user. Multiple load-cell and multiple instrument matched pair calibrations are also supported. This is often a critical advantage in precision applications like field calibration services.
Using the TEDS-Tag system, a little and inexpensive electronic identification chip is positioned within the cable that extends from the load cell or it may be mounted in the cell housing. This chip contains a unique electronic serial number that can be read from the ESL Model 4215 or CellMite to recognize the cell. The cell is then linked to the unit along with 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 your microchip. Whenever that cell is reconnected towards 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 in order that high precision matched systems can be realized. Moreover, in the event the cell is relocated 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 very small, rendering it easy to squeeze into a cable hood or cell housing.
Both ESL Model 4215 smart strain gauge indicator and 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 interfere with the cell’s signals. Pin 3 in the DS2401 is not used and will be cut off if desired. Simply connecting pins 1 and 2 from the DS2401 to pins 8 and 7, respectively, from the ESL DB9 connector will enable plug-and-play operation.
When you use off-the-shelf load cells, it is usually convenient to locate the DS2401 within the hood from the cable. The cell features a permanently mounted cable that protrudes through the cell housing. After 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 of dollars in parts as well as a simple cable termination procedure, you might have taken a typical load cell and transformed it right 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 application, the cable adapter is actually put into series with the load cell cable before it is actually connected to the Weight Sensor. It is additionally easy to make use of this technique in applications where different calibrations might be required on the same load cell. An individual may mbssap just one load cell and instrument, but could change which calibration is auto-selected simply by changing the in-line cable adapter. Since each cable adapter has a different tag identification chip, the ESL instrument will associate a different calibration data set with each in-line adapter. This can be useful, as an example, in case a precision 6-point linearization from the load cell is necessary by two different operating ranges of the identical load cell.