Obtain ECG leads without using preamplifier

[class]

Hi guys ,this my first thread

I want to know :
can i obtain ECG leads(limb leads ) without using preamplifier or differential op amp ?

**broken link removed**

can i just measure [SUB](at the same time)[/SUB] three voltage of LL[SUB](left leg)[/SUB],RA[SUB](right arm)[/SUB] and LA[SUB](left arm)[/SUB] and using RR[SUB](right leg)[/SUB] as ground
and then in the computer the leads will be obtained mathematically by using a software ?

 

[alec_t]

An instrumentation amplifier will be necessary to bring the signals up to a level which the computer can process.

 

[class]

An instrumentation amplifier will be necessary to bring the signals up to a level which the computer can process.

can i use amplifier to amplify electrode voltage?

my supervisor not allow me to use instrumentation amplifier
what can i do!

 

[alec_t]

Then you will need to use an alternative preamplifier (e.g a readily obtainable opamp).

 

[class]

can anyone give me a suggestion with some explanation ??

 

[kubeek]

You´d first have to say what the supervisor actually wants and what is the goal of this assignement.
You say you can´t use instrumentation amplifier, does that mean you can´t use a signel chip that does the job, or you you can´t use any amplifier in the instrumentaion amp configuration? Also are you sure you are not mixing up instrumentation and differential amplifiers?
What can you use?

 

[alec_t]

What do you want explained?

 

[class]

You´d first have to say what the supervisor actually wants and what is the goal of this assignement.

the main goal is to obtain ECG leads(digital by using computer)

You say you can´t use instrumentation amplifier, does that mean you can´t use a signel chip that does the job, or you you can´t use any amplifier in the instrumentaion amp configuration?
can?

yes my supervisor not allow me to use instrumentation amplifier Regardless if it it single chip or instrumentation amp configuration.

Also are you sure you are not mixing up instrumentation and differential amplifiers?
What can you use?

i not mixing .

 

[class]

What do you want explained?

i want a method to obtain ECG leads,without using instrumentation amplifier (single chip or configuration amp )

i want to obtain ECG leads by read voltage of each electrode,and then mathematically ECG will obtained(by using a software)

the problem is my supervisor is computer engineering, and have basic information about ECG
and he Insists to use this method

i told him i must use instrumentation amplifier,b but he never convince

 

[kubeek]

Ok, but is this an excersise in electronics or in digital signal processing or in biology? And can you use a normal amplifier? Because there is no way that you can sample the waveforms without one.
Yes if you measure the three voltages referenced to the RR, then you should be able to get the three "leads" by substraction.

 

[class]

Ok, but is this an excersise in electronics or in digital signal processing or in biology?

both for digital signal processing and biology

And can you use a normal amplifier? Because there is no way that you can sample the waveforms without one.

yes i can use normal amplifier,to amplify voltage of electrode

but the problem is :the voltage of electrode is about 1 Vp.p
so i can't use amplifier with gain more than 10
because the output signal will be high voltage(more than 10Vp.p), this can't measured by ADC.

Yes if you measure the three voltages referenced to the RR, then you should be able to get the three "leads" by substraction.

do you have practical method to do that??

thank you

 

[kubeek]

The problem is that most of the signal you measure is 50hz noise (just tried with my oscilloscope ), and just a tiny bit is the useful signal, so you need to sample it with huge resolution to be able to substract those two in digital and get anything else but noise.
The practical method is that you substract the two signals from each other, it doesn´t get more practical than that.

 

[class]

i saw the electrode signal on oscilloscope ,it has 50Hz ,
but it even if 50Hz removed, the signal will be about 150mVp that mean it still has a lot of noise

kubeek tahnk you very much

 

[kubeek]

You can´t really remove the 50Hz any óther way than by substracting the two channels.

 

[class]

yes that right