Field service engineers require many different load cells spanning the various ranges needed to calibrate their customers’ systems. They may also need the assortment to conduct an array of force measurements for a particular testing application. The challenge begins when the engineer must change the load cell which is connected 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 placed in the instrument.
Avoiding user-error is really a major challenge with manual data entry or with requiring the engineer to pick from a database of stored calibration parameters. Loading the incorrect parameters, or perhaps worse, corrupting the present calibration data, can cause 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 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 may be stored on the 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 many amount 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 manner. Most importantly, it is really not apparent that this calibration data that is required within your application is going to be maintained by a particular vendor’s TEDS unit. You have to also be sure that you have a means to write the TEDS data to the TEDS-compatible load cell, either 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, such as calibration systems, it ought to be noted that calibration data that is certainly stored in the burden cell is the same whatever instrument is connected to it. Additional compensation for that instrument is not included. Matched systems when a field service calibration group might be attaching different load cells to different instruments can present a difficulty.
Electro Standards Laboratories (ESL) has created the TEDS-Tag auto identification system which retains the attractive feature of self identification based 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 for the user. Multiple load-cell and multiple instrument matched pair calibrations will also be supported. This may be a critical advantage in precision applications like field calibration services.
With all the TEDS-Tag system, a tiny and cheap electronic identification chip is put within the cable that extends through the load cell or it may be mounted within the cell housing. This chip includes a unique electronic serial number that may be read through the ESL Model 4215 or CellMite to identify the cell. The cell is then connected to the unit along with a standard calibration procedure is conducted. The instrument automatically stores the calibration data inside the unit itself together with the load sensor identification number from your microchip. Whenever that cell is reconnected for 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 your particular instrument to ensure that high precision matched systems could be realized. Moreover, in the event the cell is moved to another instrument, that instrument will recall the calibration data that it has stored internally for the 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 easily offered by distributors or from ESL. The chip is very small, which makes it simple to match a cable hood or cell housing.
Both 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 does not hinder the cell’s signals. Pin 3 of the DS2401 is not really used and can be stop if desired. Simply connecting pins 1 and 2 through the DS2401 to pins 8 and 7, respectively, from the ESL DB9 connector will enable plug-and-play operation.
When using off-the-shelf load cells, it is often convenient to locate the DS2401 within the hood in the cable. The cell features a permanently mounted cable that protrudes from your cell housing. At the end of the cable, strip back the insulation from your individual wires and solder the wires in to the DB9 connector. The DS2401 is soldered across DB9 pins 7 and 8, and fits in the connector’s hood. For a couple dollars in parts and a simple cable termination procedure, you might have taken a regular load cell and transformed it right into 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 application, the cable adapter is actually placed in series with all the load cell cable before it really is plugged into the ESL instrument. It is also easy to utilize this technique in applications where different calibrations could be required on the same load cell. The ifegti may have a single load cell and instrument, but could change which calibration is auto-selected simply by changing the in-line cable adapter. Since each cable adapter features a different tag identification chip, the ESL instrument will associate a different calibration data set with each in-line adapter. This might be useful, as an example, in case a precision 6-point linearization in the load cell is required in 2 different operating ranges the exact same load cell.
Since the stress cell has become converted to a TEDS-Tag unit, it could be attached 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 within the instrument. The ESL instruments support a number of industry standard calibrations including mV/V, shunt, 2-point, or multiple-point calibration. The instrument then automatically detects the actual existence of the force sensor and matches it using its calibration data. Out of this point forward, the device is totally plug-and-play.