Posts Tagged ‘telemetry system’

A Brief Description of SCADA System Signals

Sunday, June 19th, 2011

It has been a while, I left this site without any updates. So, here I present a basic of a SCADA system signal. It’s basic and have to describe it a way earlier but, left out with an assumption every SCADA engineer should have known it. Anyway, as a general reading, this topic should be one of important information for public readers.

basic circuit of instrument signal tappingThe most common current signal standard in modern use is the 4 to 20 milliamp (4-20 mA) loop, with 4 milliamps representing 0 percent of measurement, 20 milliamps representing 100 percent, 12 milliamps representing 50 percent, and so on. The use of a 4 mA reading to indicate zero is known as “live zero.” This helps to distinguish a zero reading from a “dead signal” or non-functioning equipment. The range of readings possible for a properly functioning system then is only 16 mA (20 mA – 4 mA). This 16 mA range is known as the “live signal.” The actual reading being recorded in mA is called the “process variable.” The PV indicates a percentage of a particular measurement being monitored. The table below shows the relationship between various PVs and their corresponding percentages.

signal comparison tableA convenient feature of the 4-20 mA standard is the ease in converting these signals to 1-5 volt indicating instruments, as the table on the left shows. A simple 250-ohm precision resistor connected in series with the circuit will produce arange of readings from 1 volt of drop at 4 milliamps to 5 volts of drop at 20 milliamps. The current loop scale of 4-20 milliamps has not always been the standard for currentinstruments. In the past, 10-50 milliamp signals were used more frequently. That standard has since become obsolete. The main reason for the eventual supremacy of the 4-20 milliamp loop was safety. Lower circuit voltages and lower current levels (compared to 10-50 mA systems) mean less chance for electrical shock injuries and/or the generation of sparks capable of igniting flammable environments in certain industrial applications.

An Overview of  SCADA Signal Calculations

Definition of terms

Dead signal: A reading from a non-functioning system that can be mistaken for a measurement.
Live signal:
The range of possible process variables. In a 4 – 20 mA system, any signal below 4 mA or above 20 mA indicates malfunctioning equipment. The range of useable signals is between 4 & 20 mA. Therefore, the live signal = 16 mA.
Live zero:
A reading other than zero used to indicate zero so that a zero reading can be distinguished from a dead signal. In 4 – 20 mA systems, the live zero = 4 mA.
PV:
Process variable. The signal reading, in mA, that represents a percentage of a particular measurement.

One of the more common uses for SCADA systems is the monitoring of storage levels. Formulas for making these calculations include:

mA to feet conversion

So, given a SWH of 30 ft, and board reading of 14.67 mA, the water level would be calculated as follows:

water level calculation

Kindly, do enjoy to use or share this information. Have a nice day.

Reference: Water Opcert School

Save sensor data to Google Spreadsheets by Codebox

Saturday, December 25th, 2010

I found this is really a good way to gather data, since Google Spreadsheets is free and can be accessed from any places in the world as long as connected to the internet. Plus, you can share it with selected persons you want. It’s quite useful for scientific researchers to share and analyze their findings. Check this out (completed with the codes):

The “Hello Arduino” section in Chapter 11 of Getting Started with Processing shows how to read data into Processing from Arduino. In a nutshell, the Arduino code (example 11-6 in the book) reads data from a light sensor and writes it out to the serial port. The section then goes on to describe a number of increasingly sophisticated sketches that retrieve and visualize the sensor data using Processing’s Serial library.

This Codebox shows you how to save this sensor data to a Google Spreadsheet. The cool thing is that you can then use any of the goodies that Google provides (charts, gadgets, maps, etc) directly with your data. While the light sensor is pretty basic, you can use this basic setup to record data from more sophisticated sensors, such as a Parallax GPS receiver module into Google Spreadsheets, and then create a map of where you’ve been that you could post as a gadget.

The sketch relies on the Google API Client Library for Java, which is a set of code libraries for interacting with various Google’s services (not just Spreadsheets). In researching this article, I found Processing guru Jer Thorpe‘s article Open Science, H1N1, Processing, and the Google Spreadsheet API a great inspiration. While it’s based on an older version of the API (version 1.0, while the APIs are now up to version 3.0), it’s a great introduction to interacting with Google.

Courtesy Make

Brilliant SCADA System that failed

Sunday, September 19th, 2010

A friend of mine shared an article about software failures. it’s a good stuff to read, where we can avoid some mistakes that previously been made by software developers. there is a SCADA software there – some of the problems that I’ve been encountered too in my life. check this out:

http://images.nakedmaya.com/Troll-Link1-sm.jpgNet-Herald – a monitoring application for water supply companies. It was a complex client server application that would receive monitoring data from specialized hardware and store that data inside a SQL database. The client displays that data in different graphs, provides printable reports or sends alarm messages via SMS if a monitored value is not within its specified limits. I developed Net-Herald as a perfect fit for that specialized hardware that is provided by a local manufacturer. That way, so I hoped, I could profit from their sales leads and would find a smoother way into these water supply companies. The downside of course, was that my software would only work with their hardware. (more…)

Talking Tire Monitor detects traction & Tire Pressure

Tuesday, May 11th, 2010

tire-pressure-monitoring

Some cars have tire pressure monitoring systems for a while now, but this new system from Schrader Electronics takes that useful concept into the future.

It’s not quite explained whether this wireless Talking Tire Monitoring System actually talks to you, but one way or another it notifies you when your tire pressure is low. But it’s a whole lot smarter than that, showing you how much tread is left on those tires, and even sensing slippery road conditions in real time, notifying you how much traction your tires are getting.

In other aspect, it also could help motorists significantly reduce their carbon tyreprint as vehicles with properly inflated tyres boast an improved fuel efficiency. In addition, underinflated tyres wear out quicker and need replacing more frequently.

Courtesy Guardian via  Dvice

Distributed earthquake monitoring using laptop accelerometers

Thursday, May 6th, 2010

laptopNPRquakecatcher

This is a kind of brilliant idea, since current trends of laptops manufactured with accelerometer sensors. And this would be a large peer-to-peer earthquake warning system. Sounds like SETI@home, but for collecting data instead of processing it. From NPR.org:

Newer models of laptops manufactured by companies like Apple and Lenovo contain accelerometers — motion sensors meant to detect whether the computer has been dropped. If the computer falls, the hard drive will automatically switch off to protect the user’s data.

“As soon as I knew there were these low-cost sensors inside these accelerometers, I thought it would be perfect to use them to network together and actually record earthquakes,” says geoscientist Elizabeth Cochran of the University of California, Riverside.

So a few years ago, Cochran got in touch with Jesse Lawrence, a colleague at Stanford. They whipped up a program called the Quake-Catcher Network. It’s a free download that runs silently in the background, collecting data from the computer’s accelerometer and waiting to detect an earthquake.

Laptop accelerometers aren’t as sensitive as professional-grade seismometers, so they can only pick up tremors of about magnitude 4.0 and above. But when a laptop does sense a tremor, it’ll ping the researchers’ server. “And when our server receives a bunch of those, we then say, ‘This is a likely earthquake,’ ” Lawrence says.

No accelerometer sensor but still want to participate? That won’t be any problem since you can purchase a USB sensor for use on your desktop computers. A lot of these, reportedly, are being installed in public schools.

Courtesy: Make

Data-logging shirt for analyzing baseball biomechanics

Friday, April 16th, 2010

baseball-shirt.jpg

The shirt was developed by Marcus Moche, Alexandra Morgan and David Schmidt as a Capstone Design Project—a senior-level team project that requires students to solve a “real-world” engineering problem or develop a viable product.

Pitchers become more susceptible to injury when they lose consistency in their mechanics—the physics of how they throw the baseball, pitch after pitch. After this, is going to be logged for analysis.

Courtesy: Northeastern

Flood Triggered Automated Camera System (FTACS)

Tuesday, April 6th, 2010

flood-triggered-automated-camera-system_4.jpg

When the Department of Natural Resources of Australia decided that they needed to capture data about the natural flooding of a cave, they turned to a hacker to get results. The goal was to photograph the area during these floods with an automated system. In the end, they used a gutted Lumix digital camera mounted in a trash can, covered in aluminium foil. Though it sounds a bit silly, the final product turned out quite nice. You can see the build log, schematics, and results on the project page.

In this case the event they are trying to capture pictures of a cave flood with a Flood Triggered Automated Camera System. The system consists of a camera that is connected to a moisture sensor so that the a camera can start taking pictures when the sensor gets wet. Pictures will continue to be taken every 15 minutes until the moisture levels go back to normal. Since it is being installed in a remote location it needed to be self sustaining.

The water sensor is an interesting design since it has the ability of killing the power to the entire system when the conditions are dry. This is done by using a Darlington transistor feeding a relay.

Courtesy of Penguins Lab

Keep tabs on your car with Multidisplay

Wednesday, March 17th, 2010

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Stumble upon MultiDisplay car monitoring system. Unlike traditional systems that rely on interfacing with the OBD-II protocol and existing car computer, the MultiDisplay uses an Arduino and custom shield with a combination of sensors; including temperatures, pressures, throttle, Boost, and etc. The data collected can then be displayed on a 20×4 LCD or streamed to a PC with visualization and event recording. It’s an Arduino based open source display for interesting measurand´s of a car hosted on Google Code.

Courtesy: Multidisplay via Hackaday

Logging weight changes

Saturday, August 15th, 2009

scale.jpg

This is a classic example of a well done hack, simply for the sake of hacking. [Jorge] wanted to be able to chart his weight changes.  His solution wasn’t to simply buy a scale that could be hooked to the computer. Those are available and aren’t really that expensive. He could have even used pencil and paper to chart it in a few seconds. Instead, [Jorge] started hacking. He took apart a digital scale he already had and installed his own circuit to display weight and write the values to a CSV. The CSV resides on a removable card which can then be put in his computer to chart the data in openoffice.

source: Hack A Day

Adaptive Cruise Control Goes Mainstream

Tuesday, August 4th, 2009

pl_motor_f.jpg

Heading south on the New Jersey Turnpike, Ford Motor Company engineer Jerry Engelman swings his 2010 Taurus into the left lane to pass a semi. The Taurus hesitates, slowing down, and then Engelman adjusts his heading. The car takes off. “Larry,” he calls to his colleague in the back seat, “write that down!”

Engelman is driving, but just barely. The Taurus has a radar-based adaptive cruise-control system that lets him set a top speed and then simply steer while the car adjusts its velocity according to traffic. He’s been weaving and changing lanes, doing between 45 and 70 mph—and hasn’t touched a pedal in an hour. Over the past few years, Ford engineers have driven 60,000 miles to test, tweak, and optimize this system, which also provides collision warning alerts. They’ve been focused on the future in a financially dismal present—analysts actually praised Ford for losing only $1.4 billion in the first quarter. “It’s a tough market,” says Derrick Kuzak, VP of global product development, noting that the Taurus is important for “reestablishing us in the large-sedan market.” That’s executive-speak for “This car really needs to sell.”

source: wired.com