Logbook 7/31

 On Monday Mario and I met at his gym and he gave me the breadboard with the amp circuit built on it. He didn’t have a potentiometer so just included the last two needed resistors on the side so I could put them once I got a potentiometer. On Tuesday in Addison I went down to the lab and ran some tests.

I inputted a 100mV sinewave signal to the side where the electrodes would attach, and attached a scope probe to the output. The circuit requires +9v, -9V, and ground, luckily they do have a power supply in Addison capable of such.   I was sad to find out that the output was VERY fuzzy, and only around 100uV amplitude. I tried first at frequency of 10hz, then at larger frequencies, and the amplitude increased to 1mV as the frequency rose.

This indicates our filter is backwards, being a highpass instead of lowpass, but I don’t understand why this would be the case. I put the scope probe at different spots on the chain of amplifiers (ordered as follows: 60hz, lowpass, highpass, high gain amp). The signal became weaker after every section! There was no signal at all after the high gain amp, something was simply killing it.

I triple checked the circuit with the schematic and could findno problems.

I am going to try to get a high gain amplifier working and disregarding the filters for now. Amplification in the most import part. Hopefully Mustafa will be able to meet with me this week.