Paradigm shifts in automation are always occurring. The need for cost savings and higher diagnostics caused the shift from IP20 I/O to IP67 I/O. Now, we are in the midst of a shift to reduce or eliminate enclosures in industrial applications by removing control and power from the cabinet. With the reduction of IP20 I/O and enclosures, adding more I/O (discrete and analog) or specialty devices (RF identification, measurement devices, etc…) is now more difficult. In the past it was relatively easy, but expensive, to add another “slice” of I/O to an existing IP20 solution.
Reducing Planned/Unplanned Downtime with Vision Sensors; Part 1
One of the things I am often asked about is “why use machine vision in packaging”? There are many reasons, including dealing with the perceived complexity of serviceability and cost. I will show you where the use of vision in packaging can significantly decrease a major cost factor called “planned downtime”, along with other benefits in this 3 part blog series – so stay tuned for my later posts.
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Hit Me With Your Best Shot: Sensors Must Withstand Punishing Applications
In today’s competitive manufacturing environment, the name of the game is increased throughput. Unprecedented global competition means that industrial manufacturing machinery must be able to run better (faster, longer, hotter, etc.) and more reliably than ever before.
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8 Selection Criteria to Remember When Choosing an Inductive Sensor
Written by: Jeff Himes
Selecting the correct inductive proximity sensor for an application can be an intimidating process. There are literally thousands of models available from various vendors so having a good starting point to narrow down the field is essential.
At this point is will be assumed that an Inductive Proximity Sensor is the type of sensor being selected. If you are at the beginning of your selection process, please read and earlier blog post pertaining to your initial sensor selection.
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Get Rid of Remote I/O Cabinets Once and For All
Every time I travel, customers tell me, “we just wire everything into a box.” Every equipment designer goes through a phase of their design process where they need to decide how their I/O gets from their sensors and their valves to their controller. Some people use I/O cards on their PLC, or networks with IP20 solutions inside remote I/O cabinets.
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Capacitive Sensors – Part III
Written by: Bjoern Schaefer
The general sensing principle across this myriad of applications is nearly the same. As seen in last months post, the total amount of capacitance, as we remember, the ability to store a charge within an electrostatic field, depends on mainly three factors. Those factors are the ones which determine the success of your application.
Utility-Scale Power from Wind Requires High Reliability
The 2010 Windpower Expo & Conference in Dallas, held recently at the end of May, was a hotbed of technical and commercial activity this year. I had not attended the “Wind Show” since 2004, and I was amazed at the explosive growth of the event and overall industry in just six short years. This was a very substantial gathering, with about 1,400 exhibitors and 20,000 attendees.
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Better Alternatives to Pneumatic Cylinder End-of-Stroke Detection
There are better alternatives to detect pneumatic cylinder end of stroke position than reed switches or proximity switches. By better, I mean they are faster and easier to implement into your control system. In addition, you can realize other benefits such as commonality of spare sensors and lower long-term costs. So what are the better solutions?
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Analog Signals: 0 to 10V vs. 4 to 20 mA
In the world of linear position sensors, analog reigns supreme. Sure there are all kinds of other sensor interface types available: digital start/stop, synchronous serial interface, various flavors of fieldbus, and so on. But linear position sensors with analog outputs still account for probably two-thirds of all linear position sensors sold.
When choosing an analog-output position sensor, your choice generally comes down to analog voltage (e.g., 0…10 V), or analog current (e.g., 4…20 mA). So which should you choose?
0…10V versus 4…20 mA
When it comes to sensor interface signals, 0…10V is like vanilla ice creamr. It’s nothing fancy, but it gets the job done. It’s common, it’s straightforward, it’s easy to troubleshoot, and nearly every industrial controller on the planet will accept a 0…10V sensor signal. However, there are some downsides. All analog signals are susceptible to electrical interference, and a 0…10V signal is certainly no exception. Devices such as motors, relays, and “noisy” power supplies can induce voltages onto signal lines that can degrade the 0…10V sensor signal. Also, a 0…10V signal is susceptible to voltage drops caused by wire resistance, especially over long cable runs.
A 4…20 mA signal, on the other hand, offers increased immunity to both electrical interference and signal loss over long cable runs. And most newer industrial controllers will accept current signals. As an added bonus, a 4…20 mA signal provides inherent error condition detection since the signal, even at its lowest value, is still active. Even at the extreme low end, or “zero” position, the sensor is still providing a 4 mA signal. If the value ever goes to 0 mA, something is wrong. The same can not be said for a 0…10V sensor. Zero volts could mean zero position, or it could mean that your sensor has ceased to function.
In some cases, 4…20 mA sensors can be slightly more costly compared to 0…10V sensors. But the cost difference is becoming smaller as more sensor types incorporate current-output capability.
For more information on linear position sensors, click here.
That 1 Channel of Analog!
In most industrial applications 80-90% of the I/O going back to the PLC is discrete points. Multiple times I have been asked, “How can I easily, quickly, and cost effectively get one channel of analog back to my PLC”. The solutions in the past have either involved an IP20 slice I/O solution in a J-box, which is expensive and labor intensive, or an IP67 network module, which reduces labor costs but still carries a high cost. A common drawback to these solutions is that you have to pay for 2, 4, or even 8 channels when only one is required.