We Don’t Make Axes Out of Bronze Anymore

Every technology commonly in use today exists for a reason.   Technologies have life cycles: they are invented out of necessity and are often widely used as the best available solution to a given technical problem.  For example, at one time bronze was the best available metallurgy for making long-lasting tools and weapons, and it quickly replaced copper as the material of choice.  But later on, bronze was itself replaced by iron, steel, and ultimately stainless steel.

When it comes to detecting the presence of an object, such as a moving component on a piece of machinery, the dominant technology used to be electro-mechanical limit switches.  Mechanical & electrical wear and tear under heavy industrial use led to unsatisfactory long-term reliability.  What was needed was a way to switch electrical control signal current without mechanical contact with the target – and without arcing & burning across electrical contacts.

Example of an inductive proximity sensor

Example of an inductive proximity sensor

Enter the invention of the all-electronic inductive proximity sensor.  With no moving parts and solid-state transistorized switching capability, the inductive proximity sensor solved the two major drawbacks of industrial limit switches (mechanical & electrical wear) in a single, rugged device.  The inductive proximity sensor – or “prox” for short – detects the presence of metallic targets by interpreting changes in the high-frequency electro-magnetic field emanating from its face or “active surface”.  The metal of the target disrupts the field; the sensor responds by electronically switching its output ON (target present) or OFF (target not present). The level of switched current is typically in the 200mA DC range, which is enough to trigger a PLC input or operate a small relay.

In my next post, I will explain the do’s and don’ts for applying inductive prox sensors.

Aw, yiss…BiSS!

BiSSThere’s a cool new serial data interface coming on the scene.

It’s called BiSS (Bi-Directional Synchronous Serial), and is an open-source, free-to-license digital interface for sensors and actuators. BiSS is hardware compatible to the industrial standard SSI (Serial Synchronous Interface) but offers additional features and options. Here are a few highlights:

  • Serial Synchronous Data Communication
  • 2 unidirectional lines Clock and Data
    o Cyclic at high-speed (up to 10 MHz with RS422 and 100 MHz with LVDS)
    o Line delay compensation for high-speed data transfer
    o Request processing times for data generation at slaves
    o Safety capable: CRC, Errors, Warnings
    o Bus capability for multiple slaves and devices in a chain
  • Unidirectional
    o BiSS C (unidirectional) protocol: Unidirectional use of BiSS C
  • Bidirectional
    o BiSS C protocol: Continuous mode
  • Actuators
    o Operate actuators via two additional lines

bmlFor more information and FAQs, visit http://www.biss-interface.com/

Click here to learn about absolute, magnetically coded position measurement systems for large measurement sections with BiSS interface.

 

Optical Window Sensors

Optical window sensors are utilized where reliable part counting is needed. This type of sensor technology is based on an array of LEDs on one side, opposite an array of phototransistors on the other side. This array covers the whole area of the window’s opening with an evenly as possible distribution of light. The more evenly distributed the light is throughout the window, the higher the resolution.

Optical window sensors are usually assigned a particular term to reveal their specific functionality type. The two typical functionality types for an optical window sensor are either static or dynamic. The differences between the two functionality types are briefly outlined here.

Static functionality looks for unchanging events. In the case for an optical window sensor, static means it detects the percentage of signal blocked by an object present in or passing through the window. Dynamic functionality looks for changing events. In the case for an optical window sensor, dynamic means it detects moving objects in the window and ignores non-moving objects. Still, in either case whether static or dynamic, the sensor detects objects as they pass through the window.

A common follow-up question is: what are the pros and cons for using either functionality over the other? This is a good question, because there are definite benefits and disadvantages to both approaches. A few of these benefits and disadvantages are briefly outlined below.

Read more of this post

Asset Tracking – Top 10

The goal of plant-based asset tracking is to reduce non-productive time and asset losses, while increasing overall productivity and utilization by accurately tracking assets. Bar code and RFID technologies track changes to an asset’s location, condition, conformity status, and availability.

Balluff has been in this business for over 25 years. Based on that experience, we have compiled the top 10 list of commonly tracked plant-based assets:

1. Dunnage containers
2. Machine tools
3. Plant-floor Equipment
4. Stamping dies
5. Torque Wrenches
6. Plastic Molds
7. Storage tanks and vessels
8. IT equipment
9. Automated Guided Vehicle (AGV)
10. Modular automation sub-systems

If you are looking to gain tighter control of your assets, visit www.balluff.us/traceability

tool-room_060412

 

Error-proofing in Window Mode – Ultrasonic Sensing

In my previous post, I talked about Ultrasonic Sensors utilizing reflected mode. Window mode is an extension of the reflective mode setting. When the sensor is set up in window mode the sensor is only activated when the object target is located within the detection limit setting defined within the detection range of the sensor. So, for example a sensor that has 65…350mm operating range could be set up to see a target within 100…150mm. This mode is commonly used when target sizes require wider tolerances or size such as detecting tall to short targets or simply detecting the correct size of the target. Additionally, if the sensor selected offers an Analog output you can receive output within the new defined window.

Read more of this post

RFID – It’s Not a Matter of Privacy

With the recent boom in RFID implementations by organizations all over the globe, there is a buzz in the on-line communities and social networking sites about how the technology is an attempt to invade the privacy of every “Jane and Joe” on the planet. I have to admit when I first started to come across these public concerns I just assumed this was the vocal minority being overly paranoid. However, as the technology has progressed into many different areas of our life it has become pretty clear that little has been done to address the concerns of the public. So, I am going to address a few of those concerns here.

Recently, the GM plant in Tonawanda, NY incorporated RFID into their engine production process. They simply attach a Balluff Databolt (a specialized bolt with an RFID tag embedded in it) to every engine before it goes onto the assembly line. As with many manufacturing processes the engine will go to many different stations to be assembled and tested. At each of these stations data from the previous station is read and new data is written to the tag to ensure everything in the process went as planned. When the engine is completed the information written on the tag is uploaded to GM’s database and stored. In addition, the tag is removed, its memory erased and placed on another engine that goes through the same process. The tag DOES NOT stay with the engine. And, even if it did there would be no way to secretly track your vehicle by “pinging” this tag.

The GM example is just one of tens of thousands of applications where RFID is used to ensure quality, manage the production process, and manage product recalls in the manufacturing world. So, what about other applications like in retail where clothing is tracked via RFID or the livestock or pet industry where a small RFID tag is implanted in the animal?

Read more of this post

When to use a Vision Sensor for Error-Proofing Applications

Vision sensors are powerful Poka-Yoke tools ideal for error proofing your process. However, traditional sensors still solve more applications at a much lower cost. So, how do you decide when to jump up to a vision sensor? There are three application categories that require the use of a vision sensor, which include:

  

  1. Parts are not well fixtured: If the part is not contained in a fixture, or there is no opportunity to bring the part into an inspection station that has better tolerance, then a vision system is the best choice.
    Example: parts directly on moving conveyor belt.

    Parts on free conveyor

    Parts on free conveyor

    Read more of this post

Meeting the Challenges of Precision Sensing: Very Small Target Displacement

Fundamental application problem: Inductive prox sensor is latching on (or…failing to turn on)

  • The prox sensor gap is set to turn on when the target approaches, but it does not turn off when the target recedes (latching on)
  • The prox gap is opened up until sensor turns off at maximum target approach, but it fails to detect the target upon the next approach cycle
  • The prox sensor gap is set to turn on when the target approaches, but later on the operation becomes intermittent (prox fails to reliably detect the target)

Solution: High-performance miniature inductive prox sensor

Critical sensing performance specifications:

o   Low variation of switch point from sample to sample
o   Tight repeat accuracy of switch point
o   Low temperature drift of switch point
o   Low maximum hysteresis (distance between switch-on to switch-off)

Read more of this post

The Other Retro-Reflective Sensors

Most of the time when we think of Retro-Reflective sensors the first thing that comes to mind is a photoelectric sensor. Photoelectric offerings use a reflector to reflect light from the internally mounted emitter and receiver. Retro photoelectric sensors come in many form factors with light source options such as infrared, red light and laser types.

Ultrasonic sensors are commonly forgotten when reflective sensors are needed in a particular application. Ultrasonic sensors when set up in “Window Mode” are similar to a photoelectric sensor however the ultrasonic sensor can use an existing background as the reflective surface such as a metal plate or a solid background. The sensor simply returns a signal as soon as an object fully covers the reflector. This mode is ideal for detecting difficult targets that photoelectric sensor can have trouble with such as poorly reflective materials

ultrasonicThe example shows an Ultrasonic sensor set up in window mode. The sensor is sending a sound wave to the background (reflector) so a target can be detected when entering the detection area between the sensor and the reflector background.

For more information Ultrasonic sensors, click here.

 

 

 

Improved Feedback for Valve Actuators

Here on SensorTech, we frequently talk about the need for high performance, rugged, reliable position feedback in modern industrial applications. A recent article in Valve Magazine, entitled “The Case for Magnetostrictive” illustrates how linear feedback transducers using non-contact magnetostrictive technology help to improve the performance and reliability of valve actuators used in the petrochemical industry.

It’s worth a read. See a variety of linear feedback transducers here.

Illustration of Magnetostrictive Linear Displacement Transducer (MLDT) inserted into a gun-drilled cylinder.

Illustration of Magnetostrictive Linear Displacement Transducer (MLDT) inserted into a gun-drilled cylinder.

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