Low Cost Multichannel Data Logger

[amtex.uitm]

Hi everybody,

I need helps in designing low cost multichannel Data logger using USB to measure:
-Temperature (10 channels, range: 20 - 1700 degree celcius)
- Distortion/deformation (10 channels, range: +/- 20 mm)
- Residual stress (10 channels, range: +/- 300 MPa).

I am doing for research on Welding temperature, distortion and residual stress.
Of course, the sensors WILL NOT be placed in the "super hot" weldment.

Could some one advice or assist me to design this project and, may be, can also give me some ideas which sensors I should use for low cost budget.

Your helps are very much appreciated.

If someone is sitting around Malaysia and can help/support me, please contact me via my email.

Regards,

Amtex
(amtex.uitm@gmail.com)

 

[Acetronics]

Hi,

I'm not really sure "Low cost" and "residual stress" can be married ... as it involves Instrumentation Amplifiers ...
To give an idea ... it's quite the same as using 100 Ohms Platinium RTDs ... with .1°C accuracy ( NOT resolution ! )

I have some strain gages here:

from Tokyosokki Kenkyujo Co.,ltd. ... of course Japanese !!!

Note they are EPOXYIED on the metal ... so, it gives you the max temperature these gauges can bear ...

Alain

 

[Vizier87]

hi amtex, welcome to the forum.

You can try the ones from DataQ, they have a range of products for data logging, there is one as low as $25 but I'm not sure if they still offer it. However, you can always browse for others. They also have student benefits as well if I'm not mistaken.

Most components can be bought from Farnell or RS-Malaysia. We'll proceed more in this thread if you need more info.

 

[amtex.uitm]

Hi Alain,

thanks for your info.

What about the distortion? Do you have any idea about low cost position sensor? We would like to use LVDT but it is so costly.

For both residual stress and distortion, the sensors will be put far away from the high temperature.

 

[amtex.uitm]

Hi vizier,

you know someone in Lembah Klang who can develop the multichannel data logger for our purposes.

Thanks.

Amtex

 

[Vizier87]

hi amtex,
Here is one ready made: Data Logger Starter Kit
this one uses an RS232 port. You can buy an RS232 to USB converter to utilize it further into USB connection. You can buy two of the data loggers to fit your needs.

cheers,Viz.

 

[amtex.uitm]

hi viz,

thanks a lot for your info. Do we have distributor in Malaysia? It's not allowed to buy oversea order, only local order is allowed in our institution :-(. Did you try this starter kit? How is the performance? May be, you have also some infos about low cost sensors for measuring distortion and residual stress?
Sorry for many question coz i am very new in this field.

Thanks a lot.

amtex

 

[Vizier87]

those are the cheap ones, from Malaysia you can try via Farnell. However, I have never used them before, because we build the circuits ourselves in UM.. It's cheaper that way.

I'm afraid either you have to make an exception here, I can't find a suitable one for you in Farnell. You can inform your supervisor regarding the need to expand a bit on policies, since there are lots of specific products not sold in Malaysia actually.

I suppose if you look hard enough in Farnell's page you might find it, 'coz I browsed through it without scrutinizing each product. See **broken link removed**.

Cheers.

 

[amtex.uitm]

Hi Viz,

do you know somebody or shop which can design and develop low cost data logger around KL or Shah Alam? I read in your website that you have designed and developed LVDT. Do you have some infos about that? To save cost, I am planing to fabricate it by myself.

Thanks,

amtex

 

[Vizier87]

it's just a student project, we did manage a crude one. However, you'll find better quality ones by buying it, they shouldn't cost much. If you want to learn to develop it, it may take some time. I suggest that you see the UBW page, which allows communication of external sensors with PCs. Sparkfun also sells them. You don't need it to be wireless, am I right? So analog data from sensors can be fed into the microcontroller and you can monitor the data in your PC.

I suggest you build it yourself, by buying the discrete components and PICs from Farnell, should cost you less than RM30 to build the board. The rest of the stuff doesn't need much expertise, you won't need to know much about USB protocols and such.

If you're not up to soldering, what you need is just to buy the UBW, and the rest of your job is to configure your sensors to be fed into the input pins of the UBW, which detects analog/digital signals. The rest is just programming for the processing and display of the data.

 

[amtex.uitm]

Hi Viz,

thanks for your info. Could you please tell me where to buy cheap LVDT? We need about 5-10 units. Budget is very limited, that's why I was thinking to develop by myself.

Thanks again

Amtex

 

[Vizier87]

What is the design requirement, i.e what is the required range of detection? I can give you instructions on how to build it, it's pretty simple. However, the quality may not be the best, but it should be manageable.

It's best that you give more details on your project? What are trying to detect, what kind of medium, etc?

 

[amtex.uitm]

Hi viz..

Thanks for your support.

The required range is about +/- 10 mm. The accuracy (or might be resolution) should be +/- 0.1 mm.

FYI: we are going to measure welding distortion which can move up or down. The measurement speed can be for first trial about 20-30 measurement per sec.

Thanks,

Amtex

 

[Vizier87]

10 mm is pretty small, shouldn't be a problem. Have you considered other displacement sensors as well? Are you going to be only restricted to LVDTs?

BTW, LVDTs in Farnell cost a lot, I was wrong. They're around RM2000-3000 mostly.
There are several pages regarding construction of LVDTs, but I'm not sure whether that's what you wanted regarding your question.

Cheers.

 

[amtex.uitm]

Hi viz,

which sensor would you suggest me? LVDT is choosen, coz a lot of research on welding distortion are using LVDT. But, if there are low cost sensors, then it also ok. However, could you give me some pages about construction of LVDT?

Thanks.

 

[Vizier87]

hi amtex,

when I built the my LVDT I didn't refer to the internet, but rather the steps are all explained by our lecturer. The DIY pages are also not good for your application, I think. How much do you understand about LVDTs?

This is a basic diagram of an LVDT:
**broken link removed**

The AC voltage can be produced using a DC-to-AC circuit using a 555 timer IC, with some other components. The induced voltage detected at the secondary coils must be read with an oscilloscope for a better observation. Then, if the output is too small, then you can amplify the output (which is a sinusoidal wave) rectify it, and smoothen the output.

The rest is ADC processing in a PIC, and that'll be the UBW's job. You can write a simple Visual Basic/Delphi program to utilize the data in COM port to read the values from the PIC for data processing and display.

I know you'll need more info on this, but this is just to get you started. Pardon me if you don't understand the terminologies here, but it's pretty simple even for a layman actually, nothing to worry about here.