read a pressure sensor with my BS2

farsad

Friends:

i want to read a pressure sensor with my BS2. the sensor is a transducer and its output is voltage (0 to 100 mV). how can amplify the voltage so that i can convert it to digital signal?

Post Edited By Moderator (Chris Savage (Parallax)) : 7/23/2007 5:10:11 AM GMT

Mike Green

You use a type of op-amp (operational amplifier) called an instrumentation amplifier which is designed to amplify these low level signals. Do a websearch for "Wiki instrumentation amplifier" for a discussion. Also, please include a subject in any further postings to these forums. It's required and it helps others who may be reading your questions.

farsad

dear Mike:

thank you very much for your help.

farsad

dear friends:

the problem is that i am not very familiar with electronics. i need to know what amplifier i have to use and how to connect it to my sensor. for example i went to digikey.com to buy a opamp but i didn't know what model i need or how to connect it to my sensor. i know that it should not be that difficult but i just don't know the way.

as far as i know, the plan must be something like this:

pressure sensor (0-100mv) >> amplifier (0-5v) >> ADC0831 (analog to digital) >> BS2 stamp

and i know how to program my stamp (Basic Analog to Digital, Chapter #3, Parallax)
if i just can amplify the sensor output, i will be good to go.

so please somebody help me !

thanks

PJAllen

Near the bottom of this page -- http://www.emesystems.com/BS2rct.htm
you will find·an approach·[noparse][[/noparse] "Measuring small voltages with RCtime" ]

farsad

dear PJ:

can you please NAME the opamp that is suitable for my case?
i hope i can figure out the connections by reading the data sheet of the opamp and the link that you gave me.

Mike Green

Here's one: www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1045,P1870,D1608

Dave-W

Farsad,
There are so many to choose from. The LT1012 that I have used is one of them.

http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1100,P1221,D3013

Look at their application notes.

You can use is with a single supply but if using a +/- supply you have to take care not to go negative into the stamp. A single supply will work.

Check on the Linear.com site for you preference. Ask for a sample.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
D. A. Wreski

PJAllen

An LM741 (741) will do the job.· I think that an LM324 would be even better, it's sort-of designed for "single-ended" supplies (+V and GND).· Good, better, best -- Are lives at stake?·

Don't·finance the project by·begging for "samples," you'll have to buy some parts/components anyway, as the emesystems circuit requires that superbeta ZTX-1051 transistor (it just won't "work" with a garden-variety, general-purpose·sort.)

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=ZTX1051A-ND

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=LM324NNS-ND

farsad

dear friends:
thank you very much for your help but i still can't do that on my own! you have to do me a favor and help me more:

dear PJ:

please give me the detailed circuit map. if i can use:

>> Near the bottom of this page -- http://www.emesystems.com/BS2rct.htm
>> you will find an approach [noparse][[/noparse] "Measuring small voltages with RCtime" ]

please answer these questions:

1. the amount of R1?
2. the amount of R2?
3. what about the other pins of the opamp? is LM324NNS-ND a 14 pin IC?
4. how can i adjust the amplifier to gain the voltage as much as i want?

believe me: i need your help!

farsad

dear friends:

am i asking too many questions?! hey come on! it is not a very complicated problem. dose any body know the answer or what?

i will appreciate your help

farsad

i just cheked my private massage box and i realized that i had received some useful reply from PJ and Mike.

thank you guys and god bless you