Tuesday, March 28, 2006

a new look! finally

Finally our institute paid attention towards our web page. A new IISc web page is up. I dont know whether i am late to notice it but just now i noticed it. The facade is good! Lots of infos which were hidden inside the old page are now one click away. I liked the limk for ejournals appearing in the front page. More or less its good. I will dig up some more stuffs soon, but did you notice something; in the top corner of the page some games pic appearing. In the cricket pic some lefty batsman is hitting the ball to somewhere, guess who can it be.......... :-D

Sunday, March 26, 2006

Problems in Data Acquisition

Digital data acquisition systems have changed the world a bit! Simulated flight training, cars controlled by automatic systems are reality now. Present day research also exercises a great deal of importance on data acquisition systems. When I look around the characterization tools we use, I found most of the machines are computer controlled and I witnessed analogue to digital transition for quite a few equipment. We have our old Scanning Electron Microscope which has all the controls as buttons or knobs. Whereas, the new SEM we got has all these controls but it’s a mouse click away. One of our distinguished faculties had one mentioned that a trained Chimpanzee can operate these machines with its little finger. Surely data acquisition systems has became integral part of characterization, we no longer sit in front of DTA machine and note down the data for hours, it’s a software which does this, but here is the hitch: Data acquisition system (DAS) can easily put you in trouble if you aren’t careful. For sensitive systems which deal with high pressure or high temperature DAS needs to extremely good otherwise it may lead to catastrophe. Let’s first know where we go wrong most of the time. DAS includes four components: transducer, signal conditioner, data acquisition cards and of course the beautiful softwares. Many of us think that transducers are not a part of it and our control will be better if we have a better DAS, but in practice, the whole DAS is as good or as bad as the transducer is hence the first thing that comes into picture

1. Transducers and actuator are integral part of the DAS and a better control is possible only when a good transducer controls the machine.

2. After transducer it is the turn for the signal conditioning unit. One important feature is where to put the signal conditioner? It needs to be near the transducer as the noise is low at this point. In this regard second important point is the cable. The DA board uses similar connector as the some other ports/boards, but the design will be completely different. We have a tendency to use same connector for all application which may at times become very risky. A system should have a shielded cable in order to reduce the noise level. Wiring is important, its better to check the connection twice before starting the acquisition.

3. I will discuss ignorance here. We do data acquisition from both grounded and ungrounded sources. In case grounded source we assume our ground is at zero potential, which may not the case. Moreover, if you use transducers grounded using different ground with different potential, the data which we are acquiring will be highly erroneous. In case of low voltage measurement its quite a problem, your machine may stop working for such small problem. The punch line is use same ground for all the transducers and make sure it’s a zero potential.

4. Aliasing was one of the problems with DAS. According to Nyqist theory if signal has no frequency component above ½ the sampling rate then the signal can be completely reconstructed, and if there are frequencies above that the data will be corrupted. In practice the complete set of frequencies aren’t free from higher frequencies but there are ways to handle it, but if it goes beyond a limit it’s a problem. Suppose you are using a sampling rate of 300, and reconstructing a signal with frequency of 10 Hz, the system is absolutely fine but is its 280 Hz, well it can not show anything, that’s good but you will get a wrong result when its shows a value of 20 Hz. You have a completely wrong info. The soulution is not difficult and most of good DAS systems have this protection, a low pass filter before digitization is enough to reduce the Nyquist frequency effect, and present day most of the companies take care of it

5. Softwares! They are beautiful with all kind of flexibility to analyze the data acquired and present them in beautiful plots. The problems are in disguise, be very careful in using them and don’t belive the information you are getting without verifying it. These programs are good, but many a times they won’t consider the complexity that is hidden in your system, hence analyze the data in a wrong fashion. Its sound very general and more like software haters speak, but it is really important. Now-a-days DAS companies come up with very good softwares, still there are always ifs and buts.

I could remember few of the issues related to DAS, but there may be more and comments regarding this are really welcomed, as far i am concerned, I felt like putdown this issues.

Some interesting old articles are here:

Mistakes in DA

Article by Strether Smith

Tuesday, March 14, 2006

A day out to Muthati

Last october when Kotts was leaving for Germany, we had decided to go for a trek while he is here in March, the plan was almost spoiled but somehow we pulled out a trek to Mutthatti. We found this place through Karanataka forest dept. trekking web page. This is one of the trek places which are being explored after the death of Sandel wood smuggler Veerappan. Though it was a two day trek, we wanted to cut it short by one day. In order to save the time we went by bike. Four musketeers: Kiran, Me, Kotts and Jackie (santanu) were there for the trek, Galavalli was the only one missing (he is enjoying in US) from the group went to Narasimha Parvata last April. We sorted out our plans the previous day; reaching Muthatti was not much of a concern, only concern was biking back to Bangalore and hence we had decided to come back before Dusk that left us a trekking time of 6 hr.
We started our journey from Metallurgy dept. at IISc at around 5:30 a.m. Me and Jackie in one bike while Kiran was Kotts behind him. We went via Jayanagar and left the city via the Kanakpura road. The roads became better once we left the city! Bangalore to Kanakpura is 55 km by road and that was our first destination. We reached Kanakpura at 7: 00 a.m. and had our breakfast in a small restaurant. Kanakpura is quite big place. Our second destination was Sathnur, which is around 16 km. away from Kanakpura, and the satisfying fact was that road was really good in this stretch too. We reached there at around 8:15 a.m. Sathnur has three diversions at a circle, if you take the straight one you will reach Muthati, Left will take you to Bhimeswari and the right will take you to Cauvery fishing camp. We took the straight road. Muthati is 18 km away from Sathnur. The road was newly polished and you start experiencing bits of hills from here. It is onset of the summer and the traces of leaves on the foreground of clear blue sky appeared really beautiful. Our bikes gave a good service including one skid on the road side, except that our journey to Muthati was quite smooth. Muthati is a picnic spot like, Bhimeswari on the banks of cauvery, and like other picnic spot it was noisy, dirty with bottles and papers and chips packets. We avoided going to the river in Muthati. Instead we went to the forest office and fixed our trek route. The entry fees per head to the hills was Rs. 100/- and guide fee was Rs. 50/- per head. Mystery trails has all these details. Our guide was Mutthuraj, a young chap with cool nature. He trekked all along with us in bare feet. We started our trek at 9:30 a.m. The trails began with a thorny uphill climb. Our first trek destination was Devanamundi hills. The day was quite hot, though not unbearable. It wasn’t a very steep climbing up too. This place has quite a few specimens of wild animals we saw some signs of bear and Elephant while climbing up, but alas we couldn’t see them physically! We had to put few breaks before we reached the top of the hills. It is a typical ghats hill top: rocky and bare, no signs of shade. We took almost 2 hr to reach there. The Cauvary river valley was visible from the hill top. The river flowing by tearing apart the hills was a spectacular landscape to cherish. The complete valley was visible from there. If you have a strong eye you can identify the Chnichi water falls at extremely far away, the falls is like a white streak on the green background. I am sure sunset from that point will be a treat to watch. The peak was almost 4 km from Muthati. Our next destination was Bhimeswary, which is a place on the banks of Cauvary, hence we started descending. Almost complete trail was covered by leaf less trees! We stopped in the middle near a pond which appeared to be the main source of water for the animals; we saw a wild hare too. It was the first water body we had seen in the whole stretch. We traveled almost 3 km and there came a watch tower. We could see the basin and Bhimeswari from there. It was another 3 km before we reached the river. We found a bunch of spotted deer on the way. Mutthuraj took us to a place which was really beautiful, on the riverside. It was already 1:30 p.m. and we had to take our lunch. Kotts and Kiran prepared nice Cucumber, Pickle, Jam Sandwiches, with fruit juice, lunch became quite heavy, and so we decided to trek back to Muthati through the banks of Cauvery. I liked this stretch the most. We traveled almost 2.5 km through this trail. Both sides of the river had hills or forest and the landscape was very nice. We reached the picnic spots soon and our fun also disappeared, it was again a noisy, boozing people who were spoiling the environment. The last 3-4 km. we had to walk on asphalt road which was quite painstaking and took all our energy out by the time we reached Muthati forest office. We bade good bye to Mutthuraj and started our journey back to Bangalore. It was almost 3:30 p.m. Thanks to Kiran and Jackie we had a trouble free journey back to Bangalore. It was a nice one day trek, and a desirable break from droning campus life.

Trek route: Muthati –Devanamundi-Bhimeswary-Muthati
Distance: 15 km, approximate time: 6hr.
From Bangalore –Kanakpura (55 km)-Sathnur (16 km)-Muthati(18 km)
Approximate expenditure: per head Rs.500-600/-
Orgnized by: Kanakpura forest office ( Ph No.080-7522537)

Saturday, March 04, 2006

The small and the large colony

Sometimes back i wrote about them. I wrote about the tiny one and told the story about a big one. I did not have evidences for the big ones that is seen in my balcony. I was expecting them to come back and they certainly did! couple of days back the bees came back to my balcony for the third consecutive year. Like the migratory birds these bees somehow find my balcony! I wish there was a chance for me to build a tourist spot, i could have earned some money. It is really interesting how they come back to the same place and during same time of the year. Although the traces of their hives are wiped out each time, they build it at the same place. Mr. Ponnana from echological studies comes to remove them, he is an amazing guy, fearlessly he removes them. He has developed a technique which is an unique one, it kills less than 5% of the bees while breaking the hives. He showed me how the bees make their next destination. Once the house is under attack the few of the bees, always on their toes, run to find the next place , others find a temporary place to stay which may be a nearby tree or something that sort, once the search bees find the place the all fly to the new place. There are people who does serius resarch on this and can put much more interesting vews than this. For me, they (the bees!) are little bit of nuisance but no complains, i will peacefully share my balcony with millions of bees for next few days.