State of the Union - TEDS
Mr. Marco Peres, STP Product Manager, answers some of the common questions about TEDS, templates and versions, as well as giving a glimpse of where things are headed.
Question: What is TEDS?
Answer: TEDS is a technology that enables sensors and transducers to have their calibration information built into a little piece of memory embedded into the sensor. TEDS stands for Transducer Electronic Data Sheet. And essentially we are storing inside the sensor this piece of tiny memory. We are storing all the information relevant to that sensor, such as, the sensor model number, the manufacturer, the serial number, the calibration sensitivity and other information that relates to that particular sensor specification.
Question: Why does TEDS exist? Where did it come from?
Answer: It came from a desire of the sensor industry to move the sensors one step up. When you connect a sensor to a data acquisition system, the sensor is a transducer, it transforms a mechanical measurement, like a vibration or sound into an electric signal and in that electric signal how do you give meaning? How do you provide meaning to that voltage signal you are getting? You do that through the calibration. By enabling the sensor to have the calibration information inside of it, you guarantee that what you are measuring translates into the real thing you are measuring and you avoid errors such as entering the wrong calibration value into the data acquisition setup. You avoid things like mixing cables and mixing sensors. So essentially if you have one sensor it may be easy but there are a lot of situations where you have dozens of sensors or hundreds of sensors and to keep track of each one of them can be a very big task. By using TEDS, you make that automatic, you make that more human error proof.
Mike comment: So it sounds like you are saying that we are not only helping to ensure the accuracy of the scaling of the measurement but we are also making it easier to do the bookkeeping.
Question: How is TEDS implemented in an ICP Sensor? How is this made easy?
Answer: An ICP sensor is tiny like this one, so I brought a big one here. In an ICP sensor you have the electronics integrated into the sensor. In the case of an accelerometer, I have a charge preamplifier inside the sensor and what we have done is add a memory chip to the existing electronics so the memory chip stores the TEDS information. With ICP technology, the same two wires, that transmit the signal, can also be used to access the TEDS memory. Basically that sensor functions in two modes: the analog mode, which is used to measure the signal of the sensor itself. But I can also change that sensor into a digital mode, where essentially I am downloading that data, that specification data, that calibration data, from the sensor using the same two wires that all ICP sensors use.
Mike comment: This sounds like a very nice digital extension of the ICP analog technology that PCB Piezotronics was one of the pioneers of. It also guarantees a backward capability. So a TEDS sensor is still 100 percent compatible with all the existing equipment out there. In analog mode it works the same way.
Question: That kind of leads us to say if analog mode is the way it always worked and now there is this TEDS opportunity - lots of our community is interested in what is the state of the union? Where are we with TEDS? What is new? What is mainstream now?
Answer: Nowadays, TEDS is more and more a technology that has been adopted across the board. It started with a few transducer manufacturers and now its being embraced through more and more transducer manufacturers as well as data acquisition manufacturers. TEDS is something that doesn’t do a sensor by itself any good. You have to be able to read that information to your data acquisition. So now there are more and more companies using TEDS, just look at the IEEE website and the manufacturers that are listed there. When we started 10 years ago, there were half a dozen sensor companies. Now we have hundreds of companies that are embracing the technology and supporting the technology in their equipment. So it is pretty much like in the PC world when USB came out, USB is the technology that enabled plug-and-play. Nowadays everybody takes it for granted. You plug in your digital camera, you plug your iPhone into your computer, the computer recognizes that this is a camera, this is a media player. With TEDS it is the same thing. You plug your microphone into your data acquisition system, this is a microphone, this is an accelerometer, this is a load cell.
Question: What is the rest of the industry doing? It sounds like this is expanding to plug-and-play. Give me a little bit of understanding of what is going on through the industry.
Answer: Through the industry what is going on is you have more and more sensor manufacturers including the TEDS feature into their sensors. So when you design a new sensor you have the option to include the TEDS capability or not. More and more sensor manufacturers are adding that as a feature to their sensors, and more and more data acquisition manufacturers are doing the same thing on the other end by enabling and supporting that technology. That is only possible because TEDS is a standard. It is a standard that was written and published through the IEEE Organization. So it’s very well defined. It was published in 2004. Now it is 2011 and we have had enough time where people digested and implemented that into their equipment.
Question: Where do you see things heading? Is there a direction that is clear for the future?
Answer: There is a clear direction that TEDS is a very useful feature. It makes it very convenient. It makes it easy. It makes it plug-and-play. As companies approach and try to make their equipment easier to use and more error proof and so on, I would expect this to be adopted more and more across the board. TEDS technology was led by the sound and vibration industry but nowadays you see, for example, the load cell industry adding TEDS across the board. You are going to see TEDS in other types of sensors that we haven’t even thought about.
Question: With this amount of time and the amount of sensor types that are coming in, are there any challenges with either templates or version compatibility-things like that?
Answer: Yes there is. You always have to make sure that the sensor and equipment that you are going to use, talk to each other. Essentially, if they follow the standard, they will talk to each other. But what happens is there were some sensors that were made in the very beginning and they follow what we call the preliminary templates. There was a lot of equipment that was designed to support those templates. That is what some people call the version 0.9. That was like the Beta version of TEDS. In 2004 the standard was agreed upon and they came out with what we called the version 1.0, which is the de facto standard of what TEDS is. The question is, again, making sure that the data acquisition manufacturer, and the software and the firmware support the particular sensor you are trying to communicate with. If you buy a piece of equipment from a certain data acquisition manufacturer, if that equipment is up to date in terms of soft or hardware, chances are very high that you are going to have no issues. If you have old equipment….
Question: If a vendor supports 1.0 and the user has version 0.9 TEDS, is there a migration path?
Answer: There is a migration path. YES. Sensors can be, the TEDS memory in the sensor can be reprogrammed or updated into version 1.0. You can do that through your annual calibration maintenance of the sensor. Again, there is no reason to change anything if the sensor you have already talks to the equipment that you are using. If they work, fine, if they communicate with each other that is fine.
Question: Is there anything explaining TEDS options or templates that our community might be interested in?
Answer: There are a couple of options and templates, mostly depending on what kind of sensor you are using. For example, the accelerometer is 9 out of 10 times template 25. And that applies to piezoelectric and ICP type of accelerometers.
Question: What’s the basics of template 25?
Answer: Template 25 will list a lot of different characteristics that are common to that type of sensor. For example, if you have an accelerometer, that accelerometer can be uniaxial or triaxial. So you are going to have a few fields that define them. You are going to have the sensitivity for each of those directions. There are other templates. For example, you can have a bridge sensor like a load cell. That type of sensor would have some other parameters like the voltage power level which is unique to that type of sensor. So, different types of sensors would have different types of templates depending on the technology being used and depending on what type of information is relevant to that type of technology.
Question: Is there a lead application or example that has really turned out to be a prime benefit of using TEDS?
Answer: Yes. There are those applications being multichannel, the types of applications where you would have hundreds of channels. So in the vibration world for example, modal testing and ground vibration testing you'll see aerospace as one of the biggest examples where you have hundreds of channels and you are testing the airplane structure for modal analysis. There are applications in the automotive industry like NVH (noise vibration harshness), where you also have multichannel needs, for example acoustic applications such as holography and noise mapping techniques.
Question: If our community would like to find out more information on TEDS, where would you direct them to?
Answer: You can visit The Modal Shop website at Modalshop.com. We have a lot of information there including the Frequently Asked Questions document. There is also the IEEE website where the IEEE standard for TEDS is the 1451.4. So you can go to the IEEE website where they have a tutorial and several documents. They also have the standard that you can purchase and download from the IEEE website.