# Search results

1. ### How do you create best fit line?

Like the title says, if you have a bunch of data you can create a best fit line For example back in school, for a linear line, y = mx + c, you just need 2 points to get a line. But what if you have more than 2 points, say 10, what is the best fit line equation or how do you do it...
2. ### Difference in index refraction

What does a higher index of refraction really mean? I know about speed wavelength etc but lets say you have 2 different material to choose and ignoring other variables, and focal length, diameter are all the same between both material, would you choose a lower index refraction or higher. Thanks
3. ### Spot size and focal length lens

why does the spot size increase with lower f#. Lets says you have 2 lens of the same material, and diameter, just different focal length. F/2 has higher spot size than F/3 but F/2 is faster. Is spot size a characteristic of a lens? So if your detector is fixed in size you need to get a lens...
4. ### How do you solve 'unknown power' in an equation

Title is a bit off but i don't know what it is called. Basically, If you have something like 3.35*10^10 = (400)^(4-x) - (300)^(4-x) and you want to solve for x. Putting inside TI89, i get the answer x = -0.106072 But what if you do not have any calculator. I'm just wondering because i have a...
5. ### Solve for y - has power 4

I tried TI89 and it did not work Trying to solve for y in the following equation. I don't have a lot of software resource available to me so no matlab/mathematica/mathcad etc I'm going try in excel if it can do it. -383^(4-y) + 408^(4-y) + 297^(4-y) - 301^(4-y) = 3.358*10^10 Thanks edit...
6. ### Understanding poles and zeros

Hi, I'm trying to gain a better understanding on poles and zeros. Seems everywhere i read it says the poles and zeros can tell you the system response, characteristic and you can do lots with it from filter design to controls. Its a broad area but was hoping someone can provide further...
7. ### Guard rings for ic input

What are these? Is it like some 'physical ring' where you out a wire through it or just a connection to make both input to the op-amp common? How does this really help? Seems like you're making a source common to both like gnd so if the gnd is noisy it becomes common for both and rejects it...
8. ### Removing/creating phase lag or lead in circuit

My square wave is lagging/leading the sine wave (depending how you interpret it). i want to make the transition of my square wave be at 0 deg for the sine wave. right now the square wave transitions at 130 deg of the sine wave how can i shift this so that it transitions only at 0 deg or 360...
9. ### Signal processing and data correction

Is it possible to perform some form of data correction by finding the variance/std dev and covariance? I have a bunch data all related to a specific observation. For test purposes, i have 1000 samples of each data for certain condition. I can find the covariance between each data under this...
10. ### Getting a sine/cosine

I have a sine wave. i want to make it 90 degrees out of phase. if i remember correctly i could use a capacitor to create a phase lag of 90 degrees (like on of those motors where they put a capacitor to create the offset so it starts to turn) Do you put the capacitor in series? What value...
11. ### DPDT Question

Are there any DPDT switch that can take negative input? i want to put a sinusoidal as input and use the output to go through a difference amplifier to create a rectifier. does it work the same if i put a DC offset so i only get positive sinusoidal input to DPDT, and then use the output to...
12. ### Is there a way to create equations from numbers?

Like the topic says, is there some software or method you can use (maybe excel?) to create equations? For example if i knew my graph is going to be a straight line, and i had a few points, i can find the slope, intersection and get my equation. Then if i knew my graph is a 2nd order and i...
13. ### Getting a large change from small change

Need some help or suggestion here. I'm trying to collect some data resulting from very small changes. What i want is for example a change from 40pF to 40.5pF to result in a bigger voltage change say 0.5V to 0.8V, enough for me to see some difference. In other words, a very big SNR. The way...
14. ### Understanding impedance

I know the formulas, to some extend what impedance is. But i guess i would like to know what it really means in real world and how to use it/match it or manipulate it. Please help correct my understanding or increase it. :) High impedance is like high resistance and vice versa. You want...
15. ### What is a good lens holder material

I am just wondering what is a good material or a material i should look for when choosing to make for the lens holder. From my detector to the lens (focal length), does it need like a non-absorbing or non reflective material? When a manufacturer sells the complete camera set (regular camera)...
16. ### Reducing fringe effect, measuring values

Hi, I'm trying to measure some low capacitance using parallel plates i built. We're probably looking into the pF, say maybe 20pF (with the pcb board etc). The change in capacitance that i am really interested is very small. For the moment, i have use water as my dielectric. The capacitance...
17. ### Creating sine wave

Trying to create a sine wave. Any oscillator or chips that do it? Looking at 100kHz. Seems like most of the oscillators i find put out 0~3.3/5V square wave. But i am m looking for -2.5~2.5V 100kHz sine wave output. I would think the chips create the square wave by taking the sine wave and...
18. ### Capacitor measurement and understanding

Hello everyone, I'm trying to find more information to get a better understanding on capacitors. I made a small parallel plate capacitors basically to use it as a sensor and for data collection/analysis to see if there is any correlation with my ongoing research. The capacitor formula C=...