Industrial sensors used for continuous position or process measurement commonly provide output signals in the form of either an analog voltage or an analog current. Both are relatively simple interfaces, but there are things to consider when choosing between the two.
Industrial sensors with current output are typically available with output ranges of 0 to 20 mA, which can be converted to 0-10 VDC by using a 500 Ω resistor in parallel at the controller input. Output ranges of 4 to 20 mA, which can be converted to 1-5 VDC by using a 250 Ω resistor in parallel at the controller input. Although it requires a shielded cable, current output allows use of longer cable runs without signal loss as well as more immunity to electrical noise. It is also easily converted to voltage using a simple resistor. Most, but not all, industrial controllers are capable of accepting current signals.
Industrial sensors with voltage output are typically available with output ranges of:
0 to 10 VDC (most common)
-10 to +10 VDC
-5 to +5 VDC
0 to 5 VDC
1 to 5 VDC
One of the main advantages of voltage output is that it is simple to troubleshoot. The interface is very common and compatible with most industrial controllers. Additionally, voltage output is sometimes less expensive compared to current output. With that being said, compared to current signals, voltage signals are more susceptible to interference from electrical noise. To avoid signal loss, cable length must be limited. Voltage output also requires high impedance input and shielded cable.
As we wrap up the old and begin to open up the new, let’s take a moment to reflect on what this past year has brought us. Apart from the triumphs and the hard lost battles, we want to bring you some of our top posts from 2015. These posts are as follows:
Who doesn’t like complicated concepts broken down into easy to understand terminology? In this post we break down the differences between point level detection and continuous position sensing as well as provide you with technologies to put into practice.
So you just got a brand spanking new 2-wire sensor for the holidays but you realize you don’t know exactly what wire goes where. In this post we make wiring that bad boy easy and even break down what polarized and non-polarized mean.
So we have covered four of the top posts from 2015, are you ready for the number one post from the past year? So are we! And we will have it for you right after a quick message from our sponsors! (just kidding!)
Through the use of magnetic induction, we are able to reduce the downtime of a machine due to the failure of a slip ring. Inductive couplers pass power and data over an air gap creating a maintenance free, non-contact environment to operate a variety of machinery.
We want to thank you for the wonderful year that is behind us and be sure to be on the look-out for even more exciting news to come this year!
There has been a lot of talk in the industrial automation about RFID. In past blog posts we’ve discussed topics like RFID ROI and when to use IO-Link RFID. We could talk about things to consider when implementing RFID into your plant or different applications for days. In this entry, though, I’d like to get back to the basics a little bit.
Area of Application for a Passive RFID System:
RFID is used to accurately identify an object on which the tag is placed. In addition to identification, bject-specific information, like maintenance data is contained on the tag.
How It Works:
Since passive RFID tags contain no battery, the tag is powered up or “woke up” by the RF waves emitted from antenna of the same frequency. Once a tag is located in range it is powered up by the antenna and its memory can be read and transmitted to the processor. The time it takes the reader to extract information from the tag is usually measured in milliseconds.
Three Main Components of a Passive RFID System:
Tag – A combination of a chip and internal coil. The chip is where the data is held in the memory and can contain a few bytes of data or thousands of bytes of data depending on the capacity of the chip.
Antenna – Connected to the processor by an external cable or sometimes contained inside the same housing, the antenna transmits the data to and from the tag back through the processor
Processor – The role of the processor is to organize the data as it is being read or written. The processor is usually connected to a controller, like a PC or PLC, and performs the task issued by the controller.