The iphone is for more than Angry Birds… Apps for Engineers

Recently I came across this link on control engineering’s website and I just had to share it.  They have created an app that organizes and summarizes all the available useful apps for an engineer on the go.  From Autocad/Solidworks reference tools to basics on engineering topics to standards document references they have collected the perfect library for you to find the tools you need and maybe didn’t know existed.  And in the long run I think the goal is to make us more productive, even when sitting in baggage claim waiting for our toolbox.  As for me, I can’t wait until April when I can trade in my blackberry and get my iphone to give this app a spin.

Take a look at their offering, let me know what you think.  What apps are you using today for your designs?  What apps do you wish were out there for engineers?  Which apps should I download first?

The Forgotten Proximity Sensor

If someone says proximity sensor, what is the first thing that comes to mind?  My guess is inductive and justly so because they are the most used sensor in automation today.  There are other sensing technologies that use the term proximity in describing the sensing mode.  These include diffuse or proximity photo electric sensors that use the reflectivity of the object to change states and proximity mode of ultrasonic sensors that use high frequency sound waves to detect objects.  All of these sensors detect objects that are in close proximity of the sensor without making physical contact.

One of the most overlooked or forgotten proximity sensors on the market today is the capacitive sensor. Why? Perhaps it is because they have a bad reputation from when they were released years ago, as they were more susceptible to noise than most sensors.  I recently heard someone say that they don’t discuss capacitive sensors with their customers because they had a bad experience almost 10 years ago. With the advancements of technology this is no longer the case.

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Basic Operating Principle of an Inductive Proximity Sensor

Did you ever wonder how an Inductive Proximity Sensor is able to detect the presence of a metallic target?  While the underlying electrical engineering is sophisticated, the basic principle of operation is not too hard to understand.

At the heart of an Inductive Proximity Sensor (“prox” “sensor” or “prox sensor” for short) is an electronic oscillator consisting of an inductive coil made of numerous turns of very fine copper wire, a capacitor for storing electrical charge, and an energy source to provide electrical excitation. The size of the inductive coil and the capacitor are matched to produce a self-sustaining sine wave oscillation at a fixed frequency.  The coil and the capacitor act like two electrical springs with a weight hung between them, constantly pushing electrons back and forth between each other.  Electrical energy is fed into the circuit to initiate and sustain the oscillation.  Without sustaining energy, the oscillation would collapse due to the small power losses from the electrical resistance of the thin copper wire in the coil and other parasitic losses.

 Inductive proximity sensor cutaway with annotation Read more of this post

Position Monitoring with EtherCAT

Much has been written here on SensorTech about the value of industrial networking in the machine automation realm.  As the trend towards industrial networking continues to expand, we see more and more network-capable sensors coming to the fore.  Linear position sensors are no exception.

Network-connected linear position sensors take the concept of continuous, absolute linear position feedback a step or two forward by allowing the position sensor to be directly connected to the network, and also providing additional information in the form of sensor-level diagnostics.

Two such examples of network-connected linear position sensors are the newly introduced Micropulse EtherCAT position transducers.

Available in two varieties, one for basic position monitoring, and one capable of closed-loop positioning tasks, the Micropulse EtherCAT transducer is a good example of the continuing evolution of basic sensors towards more “intelligent” network-capable sensors.

For more information on industrial networking products, start here.

Level Detection with Ultrasonic Sensors

Liquid measurement can be a demanding application therefore selecting the most effective sensor technology is imperative. Ultrasonic sensors are the ideal solution for distance measurement or position detection of granules, fluids and powders. They measure fill levels, heights and sag without making contact as well as count and monitor the presence of objects. They are extremely versatile, operate independently of color and surface finish, and are not affected by transparent objects that generate strong reflections. And because they are not affected by dust, dirt and steam, they are the ideal choice for critical applications.

Ultrasonic Sensors operate with propagation of sound waves providing a reliable detection source for level detection applications where liquid measurement monitoring is necessary. They will enhance the flexibility of the application with additional advantages of being a non-contact sensor so there are no mechanical floats or arms that can retain residual liquid build up. This residual material can cause machine application downtime as interruption of production is needed to maintain and clean the mechanical monitoring system. Because the distance to the object is determined via a sound transit time, ultrasonic sensors have excellent background suppression. With their transit time measurement, ultrasonic sensors can record the measured value with highly precise resolution (some sensors to even 0.025 mm). Ultrasonic Sensors can monitor
and detect nearly any liquid.

Level Detection with Ultrasonic Sensors2Level Detection with Ultrasonic SensorsAn ultrasonic sensor is not affected by the color, transparency or glossiness of a surface. They can reliably detect bulk materials, liquids and material surfaces. Good reflective materials include:

  • „„ Water
  • „„ Paint/varnish
  • Wood
  • Metal
  • Plastic
  • Stone/concrete
  • Glass
  • Hard foam rubber

Additional advantages ultrasonic sensors provide when monitoring liquid is their ability to have two independent outputs programmed into one sensor. This is a great way to monitor upper and lower liquid levels with one sensor. This sensor feature allows one independent output setting to indicate a minimum level and the second output to indicate a maximum level concurrently providing constant feedback along with a voltage or current output.

WOW! It’s a bolt!?

Our Databolt never fails to grab the attention of everyone who has ever ventured to take a look in my sample case. In a kit of a hundred plus RFID tags which vary in frequency and form factor, it’s the one that draws the most questions, by far. Without a doubt, it is unique, it is rugged, and it is a pretty ingenious method of attaching an RFID tag to an item that needs to be identified and tracked through a process.  However, I couldn’t help but think…it’s just a bolt.

If you have ever been to a manufacturing trade show then you know that the “wow factor” is pretty common in this industry. From Blackjack dealing robots to machines the size of a typical suburban home, you must admit there is some impressive stuff out there.

Never did I consider the Databolt a “wow” product until a recent issue of Popular Mechanics featured the Balluff Databolt in an article regarding RFID traceability at GM’s engine plant in Tonawanda, NY. After reading the article I realized that wow can mean different things. So when I see a friend I haven’t seen for fifteen years and the first thing they say is wow. Is it wow, I haven’t seen you for a long time? Or wow, you’ve gained sixty pounds and are losing your hair? I guess it is to be left open for interpretation.

My vanity aside, it is now pretty clear that when the Databolt produces a wow, it is not necessarily a wow, this is the coolest piece of technology I have ever seen. More accurately, it is most likely wow, this simple little bolt can save my company millions by:

  • Creating visibility into the production process
  • Helping to comply with regulatory and quality standards
  • Proactively managing product recalls with near-real-time corrective action
  • Improving customer safety and satisfaction
  • Reducing the cost of nonconformance

So, that is my take on what people really mean when they say “wow” in regards to the Databolt. Check out the article and determine for yourself how wow should be interpreted.

http://www.popularmechanics.com/cars/news/industry/this-bolt-is-the-key-to-gms-high-tech-assembly-line-16324897

Pathways to More-Precise Linear Motion

In a previous SensorTech post, we discussed improving the accuracy of linear motion systems while lowering total system cost by employing external linear position encoders as secondary feedback.  The secondary feedback supplements the primary feedback provided by a rotary encoder mounted to the drive motor.

Now Clint Hayes, Sales and Product Manager for Linear Technologies at Bosch Rexroth, has written an excellent “How To” article for Machine Design magazine entitled “Six Keys to More-Precise Linear Motion.”  Mr. Hayes identifies precision as a combination of accuracy and repeatability, where accuracy is the discrepancy between target and actual position, and repeatability is the ability of a motion control system to return to a given position when repeatedly approaching that position from the same direction   He discusses the important effects of various mechanical design elements and operating conditions for linear guides that can influence these important motion control system specifications.

One of the important specifications discussed in the article is Positioning Accuracy.  Mr. Hayes points out that positioning accuracy is dependent on the capabilities and tolerances of the mechanical drive mechanism.  He also highlights the technique of implementing electronic position correction to compensate for rising mechanically-induced deviation as travel distance increases.

The reference measurement for this electronic correction can be derived from an externally mounted linear scale encoder.  The external encoder provides actual load position data that the motion controller uses to calculate the required amount of correction needed to compensate for the non-linear mechanical deviation over distance.

If you’d like to know more about the benefits of external position feedback, there’s a White Paper available called “Motion Control Primer: Direct load position sensing with secondary feedback encoders”.

Are you taking a chance with low-cost sensors?

Don’t take chances with low-cost sensors. Some companies have been severely scaling back on sensor quality to meet price targets. Be on the lookout for these telltale signs of poorly engineered or manufactured sensors:

  • Varying sensing distance: to drive out costs, some manufacturers are eliminating the final distance calibration step. This means the actual sensing range can vary up to 30% from the specifications.
  • Temperature compensation: affecting mostly inductive proximity sensors, this is one of the more technical areas of sensor design. Special circuits and design methods eliminate the large operating distance variation seen with some low-cost sensors.
  • Adequate electrical protection: there are numerous methods to protect a sensor’s output circuit, not all are created equal. Many do not take into account overvoltage, overcurrent, short-circuit, reverse supply polarity, mis-wiring, and energy backfeed from the load.
  • EMI resistance: influence from electro-magnetic interference (EMI) noise can cause false triggers leading to machine malfunctions. It takes years of experience and testing to make sensors that will operate reliably near motors and drives.

Fortunately, there is an answer to these potential problems: the Global line of sensors offered by a reliable sensor manufacturer with decades of proven experience. These products are not built down to price, but instead are built up to the highest standards in the industry. By utilizing highly automated product lines and funneling usage to fewer part numbers with broader application potential, the Global line is one of the most cost-effective sensors programs available today, and without sacrificing any quality or reliability. Bottom line? You don’t need to sacrifice quality or reliability in order to meet your cost budget. For more information, see the entire Global line here.

global

Stop Industrial Network Failures With One Simple Change

Picture1

It’s the worst when a network goes down on a piece of equipment.  No diagnostics are available to help troubleshooting and all communication is dead.  The only way to find the problem is to physically and visually inspect the hardware on the network until you can find the culprit.  Many manufacturers have told me over the past few months about experiences they’ve had with down networks and how a simple cable or connector is to blame for hours of downtime.

2013-08-19_Balluff-IO-Link_Mexico_Manufactura-de-Autopartes_healywBy utilizing IO-Link, which has been discussed in these earlier blogs, and by changing the physical routing of the network hardware, you can now eliminate the loss of communication.  The expandable architecture of IO-Link allows the master to communicate over the industrial network and be mounted in a “worry-free” zone away from any hostile environments.  Then the IO-Link device is mounted in the hostile environment like a weld cell and it is exposed to the slag debris and damage.  If the IO-Link device fails due to damage, the network remains connected and the IO-Link master reports detailed diagnostics on the failure and which device to replace.  This can dramatically reduce the amount of time production is down.  In addition the IO-Link device utilizes a simple sensor cable for communication and can use protection devices designed for these types of cables.  The best part of this is that the network keeps communicating the whole time.

If you are interested in learning more about the benefits that IO-Link can provide to manufacturers, please take a look at this flyer.

Direct load position sensing with secondary feedback encoders

Motion control system designers have found a way to eliminate or reduce common sources of position error, such as mechanical backlash, non-linearity, and hysteresis.  The method is called direct load position sensing and it employs linear encoders as a source of secondary position feedback.  Secondary feedback encoders supplement the indirect position measurement taken by a rotary shaft encoder by measuring the position of the moving load directly.

This method can save money by delivering the specified motion system performance at lower initial cost, and helps maintain system performance over time by getting around the problem of mechanical wear and tear degrading the accuracy of position measurements taken at the motor.

If you’d like to know more, there’s a White Paper available called “Motion Control Primer: Direct load position sensing with secondary feedback encoders”.

linear-actuator-with-encoder

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