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Support in learning the art of electronics
rstofer:
--- Quote from: Mule on July 21, 2017, 12:15:16 pm ---I need help in setting up the very first circuit in 2L. I have 2 BNC leads, a function generator and a scope.
I know this seems very basic but how can I drive my RC circuit with the function generator?
What do I need to be careful of? I don't want to go breaking anything.
Cheers,
--- End quote ---
Hook it up like they show it...
On the left, connect the signal generator input output leads - hot (usually red) to the resistor, ground to the common ground (3 connections should be shown tied together at this point in the book).
On the right, connect the scope probe to the junction of the resistor and capacitor, scope ground to the common ground.
At this stage in the learning process, I would be happier if they showed the 3 ground connections tied together.
Mule:
Ahh yes all so obvious now. Thank you very much.
coolyota:
Hello, I am attempting to do the lab 1L.3 on page 27 but very confused of what to do. It says we are making a voltmeter but doesn't have instructions or parts I need. What am I supposed to do for this section of LAoE? :palm:
rstofer:
1) you need a meter - say 0-1 mA full scale
2) you need to calculate the internal resistance by building a voltage divider with, say, a 1k divider resistor and a variable voltage source 0-2V (or 10k 0-12V). Anything that is adjustable and can provide 1 mA while including the unknown internal resistor
3) set your variable power source to just move the needle to full scale and measure the output of the voltage source
4) calculate the internal resistance from the voltage divider equations by first calculating the total resistance from your measured voltage divided by 1 mA. Then subtract off the divider resistor and what you have left is the internal resistance
5) now that you know the internal resistance, you can compute voltage divider resistors for various ranges like 0-1V, 0-10V, 0-100V and so on.
rstofer:
If you don't have a meter, you can use a DMM on some low current measurement range. I can set my Aneng 8008 (cheap meter) for a range of 0-9.999 mA so I can know exactly where 1.000 mA comes up.
Personally, I would use the DMM even though the instructions recommend a bare meter. That's fine, if you happen to have one. Not so fine if you have to go buy one.
If you buy a quality meter, like a Simpson, you can go to their catalog and find out what the internal resistance is supposed to be. Kind of a cross-check on the calculation. If you buy a meter from Yuan-Hung-Low, you're on your own.
Page 5 shows a 0-1 mA meter as having 43 Ohms of internal resistance. If I want to measure 0-100V then I need to figure a total resistance of 100 V / 1 mA = 100,000 Ohms. My meter accounts for 43 Ohms so I need a 99.957K resistor. 99.95 seems to be available at DigiKey Part number Y145399K9500A9L-ND 0.05%
Available but not in stock and it looks like you have to buy 2500 at a time. I would use 100k and call it good enough.
https://www.simpsonelectric.com/images/File/datasheets/widevue_datasheet.pdf
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