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Okay, good day everybody. My name is Maria and today I will start the lecture and then

Professor will join us a little bit later. So a brief recap from last week. The professor

was talking about measuring heart sound signals, then human speech, all different possibilities

that you can like CTG, then magnetencephalography, then vibrations when there is joint movement

and so on. And with that you actually concluded the generation of biomedical signals part.

So today we will start the second part, the measurement of the biomedical signals. So

now that you know what you can measure, we will go how you can measure it. And first

we will start with measurement possibilities. Mostly we will be talking about the electrodes,

so how you can measure biomedical potentials. Then we will talk about a little bit ECG measurement,

then sources of the measurement errors, which is very important to know in order to know

how to filter them or how to deal with them. And then the professor will talk about measuring

of the movement. So the best way usually to start is with the definition. So the measurement

is a collection of quantitative data. The measurement is made by comparing a quantitative

with a standard unit. And actually I really like this definition because it really hits

the bull's eye that the measurement is comparing the quantity with the standard unit. And of

course this comparison cannot be perfect, so the measurement always have some errors. And

also I would like to add that you should be aware that your recording system, that your

measurement system will also have some limits in the sense that you need to know how precise

you can measure one thing. For example, if you want to, you go to doctor and he measures

your blood pressure. You can see that there is like scale that he, with which he is measuring.

So for example, he can't say your blood pressure is 120.5 because he can't see that 0.5. The

smallest signal that he can measure is usually 2. So the measure scale is increased by 2.

So he can't measure that precise. If you want to measure something with more precision,

you need to use other sensors, other measurement systems. But whenever you are measuring something,

you really need to know what is your limits. And of course what you are measuring with

which precision you want to measure things. Okay, so let's start with measurement possibilities.

You should distinguish between in vivo and in vitro measurements. Where in vivo is actually

measuring of living subject. It can be human or animal or plant. And the important thing

is that your measuring part is not extracted from the living human or subject. So if you

are measuring, if you take, for example, cancer out and measuring something on that cancer,

it's not in vivo because it's not still in the human. Okay, so whether you are measuring

in vivo or in vitro, you will use biomedical sensors. And with those sensors, you will

actually measure either physical, electrical, chemical, or biological quantities. And in

order to measure them, you will actually need the transducers. So device that you let actually

convert your quantity into the measurable, usually electrical signals. If you want, of

course, to store that on the computer and use it as a digital signal. But for example,

in my research field, I use optical sensors for measuring carotidogram. But so the pulsation

is transduced to optical signal. But then if I want to store it in the computer, I also

need to use a transducer that will convert that optical signal to electrical. So by the

end, you usually end up with transducing to electrical signals at the end. So transducers

can be seen as sensors that are actually converting physical parameters to electrical output or

as an actuator. So it's other way around. They are converting electrical signals to

physical output. But for measurement part and for things that we are going to talk today,

we use sensors. So what are the things that we can measure? So we can measure dimensional,

mechanical changes, chemical changes, electrical changes. And when we are talking about biomedical

signals, we are mostly talking about measuring biopotentials, which is actually measuring

electrical changes. So in order to make an interface between the body and the measuring

system, you need to have the transducers that will convert the current of the ions. Because

if you remember in the body, there is a current that is carried by ions. And in cables, the