97 votes
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Duracell PowerCheck - How Does It Work?

According to the German Duracell website: As you press the points, a current will flow through a metal strip getting warm. The display is a thermochromatic one. So the increased temperature will ...
Arsenal's user avatar
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54 votes
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Why is the voltage measurement of this circuit different when the switch is on?

First of all, well done for doing the practical experiment. It's good to see people trying things and wanting to discover the answers to their observations. It may be easier to visualise this with a ...
MCG's user avatar
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38 votes
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What is the voltage range of a standard headphone jack from a phone?

Commercial line out specification is to be able to drive 1 milliwatt to a 600 ohm load. For a sine wave, this means a voltage of 0.77 volts RMS (2.2 volts peak-to-peak) and a current of 1.3 ...
PkP's user avatar
  • 7,677
37 votes

Measure voltage with no current

Neat physics solutions aside, the practical way to do this is with a very low input bias current op-amp running in a buffer configuration. One of these op-amps with a properly designed layout can draw ...
Synchrondyne's user avatar
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37 votes
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Determine voltage drop over 10G resistors with cheap multimeter

Do what the ancients did ==== use a Wheatstone bridge. Like this simulate this circuit – Schematic created using CircuitLab Rotate the 10,000 ohm potentiometer for ZERO reading. Then measure ...
analogsystemsrf's user avatar
36 votes

Circuit for measuring high voltage DC voltage (up to 1000V)

A resistor divider will do what you want, but at this voltage there are some issues you can normally ignore: The top resistor has to be able to handle 1 kV. Those are harder to get than "ordinary" ...
Olin Lathrop's user avatar
35 votes

Multimeter exploded during ACV measurment - What did I do wrong?

Ok, let's first get some things out of the way that may have to do with misapplication of a multimeter... Depending on the exact type of multimeter you use, your mileage may vary, but here's my guess ...
zebonaut's user avatar
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28 votes
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Why does battery voltage slowly return to the open voltage?

The main reason is the time it takes for the active chemicals in the cell to diffuse into the electrodes and reaction products of the chemical reactions to disperse. The active chemicals are consumed ...
Kevin White's user avatar
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27 votes
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Can anyone identify this circut?

If you sum the capacitors to just one, then it looks like an envelope detector. If you put capacitors in parallel then you can sum them together to just one. $$C_{tot}=C_1+C_2+C_3+C_4$$ And then you ...
Harry Svensson's user avatar
24 votes

What is the voltage range of a standard headphone jack from a phone?

Unfortunately there is a lot of "audiophile" nonsense around headphone amplifiers and headphone impedance. Probably the top 5 results for "headphone impedance" on Google are just wrong. This site ...
Timmmm's user avatar
  • 1,183
23 votes

Why is the voltage measurement of this circuit different when the switch is on?

This is an extremely nice experiment! I have an idea to add to jonk's comment: It is super-good that you are testing out what happens like this! As already provided, the answer is that the battery ...
Marcus Müller's user avatar
23 votes
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How do I know if a wire is floating or not?

So what tool/method should i use to check if wire is floatinf? Measure the voltage when the pin is pulled to Vcc by a high value resistor, like 100K. Make the same measurement when the pin is pulled ...
ErikR's user avatar
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22 votes
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How to read 0 -10V analog voltage with lower voltage tolerant ADCs without a voltage divider

However because this is for a prototype that should be up to Industrial safety standards, my boss wants me to isolate the 10V from the 3.3V logic. I question your boss's logic when it comes to ...
Marcus Müller's user avatar
21 votes
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Reasons not to use these leads

In addition to the excellent answer given by @JorenVaes there is also a simpler electro mechanical reason for this caution. If you take a close look at the lead connections for the 34xxxA multimeters ...
Michael Karas's user avatar
21 votes

Why is my 50-600V voltage tester able to detect 3V?

plugging it into a 120V outlet means there should be a 3V drop across each bulb, so my 50-600V tester shouldn't be able to detect that Your tester is not detecting the voltage drop across a bulb, but ...
Chris Stratton's user avatar
19 votes
Accepted

Does an oscilloscope subtract voltages as phasors?

The math subtraction function in an oscilloscope subtracts the instantaneous values of waveform 1 from the instantaneous values of waveform 2 to create a new waveform comprising all those ...
Andy aka's user avatar
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19 votes
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What does the horizontal bar indicate in the DMM display?

That bar at the bottom of the screen simulates an analog meter - the length of the bar increases with increasing digital readings. It is often easier to observe a varying voltage by looking at the ...
Peter Bennett's user avatar
16 votes

How do I measure a voltage greater than 5 V with Arduino?

Step down the voltage with a resistive divider and buffer it with an rail-to-rail input and output op-amp wired up as a voltage follower. This buffers the resistance in the resistive divider from the ...
DKNguyen's user avatar
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16 votes

Are there any tricks for measuring high voltages (~1000 V) efficiently?

Battery powered designs prefer voltage dividers with large resistance values. ADCs want low output impedances. An expedient way to lower the output impedance of a resistive divider is to add a ...
Nick Alexeev's user avatar
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15 votes
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How can I collect data from a hydrophone?

Basic parameters To summarize, you want to log a analog signal of up to 100 mV amplitude at 10 kHz sample rate. That's quite doable. You want to collect data for up to "weeks". Let's see how much ...
Olin Lathrop's user avatar
15 votes

How can I collect data from a hydrophone?

You need three things: an amplifier (sorry, unavoidable), an ADC, and some digital storage. With the quality of modern op-amps, you totally do not need to be concerned about noise and distortion; you ...
William Brodie-Tyrrell's user avatar
15 votes

Reasons not to use these leads

The 3458A is an 8 1/2 digit, calibration/metrology grade instrument. When measuring 1V, your least significant digits will be nanovolts. At this level of accuracy, you need to pay attention to ...
Joren Vaes's user avatar
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15 votes
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Is it normal for a lithium ion battery to read with a very low voltage on a multimeter?

Almost any charging circuit for Lithium batteries has a low voltage protection built in. This will protect against charging dead batteries (which might overheat) and this also inhibits enabling the ...
le_top's user avatar
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15 votes
Accepted

Can I use capacitor to measure time?

Yes, this is a well-established method of measuring with resolution in the picoseconds without requiring impossibly high clock frequencies. You switch a current source to a capacitor. The generic term ...
Spehro Pefhany's user avatar
14 votes

Measuring a small resistance, ~0.001 ohm

You can't "accurately determine" such a low resistance using household DMMs, which are likely completely lack of any calibration whatsoever. Accuracy class of your household DMMs is way worse than 1%, ...
Ale..chenski's user avatar
  • 40.5k
14 votes

What does the horizontal bar indicate in the DMM display?

From the Fluke 87V datasheet page 11 point 18 : The number of segments is relative to the full-scale value of the selected range. In normal operation 0 (zero) is on the left. The polarity ...
Sorenp's user avatar
  • 1,287
14 votes

What does the horizontal bar indicate in the DMM display?

The bar is a fast-responding 'analog meter', that can be useful for following variations in the input voltage, for instance when you're adjusting a circuit with a potentiometer in real time. In the ...
Neil_UK's user avatar
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14 votes
Accepted

What is the voltage drop across the 10 ohm resistor?

Millman's theorem is a kind of multi source voltage divider theorem based on this topology: - So, re-arrange your circuit to use a 3rd source that is actually 0 volts and you're good to go: - Hence \...
Andy aka's user avatar
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14 votes
Accepted

Measuring high voltage with a microcontroller

simulate this circuit – Schematic created using CircuitLab The resistors divider works always exactly the same. For very precise measurement you need a low TCR value resistors. The tolerance ...
Marko Buršič's user avatar

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