# Questions tagged [voltage-measurement]

Act of measuring voltage

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### Duracell PowerCheck - How Does It Work?

I've been using these batteries for a long time and I've never seen such a feature. There's a band on its outer wrapping having two ends: The white circle on the left side and the another one on the ...
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### What is the voltage range of a standard headphone jack from a phone?

I want to connect the output from the audio jack of an iPhone to an Arduino. What voltage range can I expect to see on the audio lines from the iPhone? I assume that turning the volume up on the ...
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### Why is the voltage measurement of this circuit different when the switch is on?

I built a simple circuit with two lamps and a slide switch powered by two 1.5 V batteries. When the slide switch is off, the voltage of the circuit measured by a multimeter is 3.15 V: However, ...
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### Multimeter exploded during ACV measurment - What did I do wrong?

simulate this circuit – Schematic created using CircuitLab A DT-830B meter. I bought a new transformer, and I was trying to measure the output voltage. I plugged the probes on 'VΩmA' (not 10 A)...
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### Why can a voltmeter still measure potential difference if it has a (theoretically) infinite resistance?

I am a physics teacher who did engineering and hated all things electrical! Hence when my students sometimes ask me how a voltmeter can measure the potential difference between two points if there is ...
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### Measure voltage with no current

Suppose I have a capacitor and I want to observe its charge decay over time. How can I do that without affecting its discharge rate through measurement? AFAIK a typical voltmeter runs current ...
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### Circuit for measuring high voltage DC voltage (up to 1000V)

I am a final year E&E student and I am trying to built a power meter that must be able to measure quite high DC voltages, up to 1000 V DC. I am measuring with a simple 12-bit ADC that has an ...
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### What value does ammeter or voltmeter measures (RMS, Average or Peak )?

What value does these meters measure? Is it RMS, Average or Peak value ?
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### Determine voltage drop over 10G resistors with cheap multimeter

I have two 10G resistors connected in series with a 3V battery. I want to determine the voltage drop across one of them, which of course is 1.5V. When I use my multimeter to check the voltage drop, it ...
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### Is it normal for DC wall adapter power supplies to provide voltages above the nominal ones?

When I measure a 9V DC wall adapter power supply with a multimeter it shows 11.8V. When connected to my board this voltage lowers to 10V. Is this normal? Should I be afraid of toasting my 1117CD-5.0 ...
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### How does a smart phone measure battery percentage?

A smartphone (assume it to be an Android) usually displays the battery percentage from 0 to 100%. I am assuming that this is the usable capacity of the battery. I have several questions: How exactly ...
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I'm doing some testing on a battery (MC002787). I've noticed that the voltage after a load takes a few minutes to go back to the open voltage (voltage without load for a long time). Can anyone explain ...
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### High speed passive probe - contradiction between authors or different points of view?

In a document Hiscocks et al. describes some basics of Oscilloscope probe theory. The document is very understandable and seems coherent. Notice in particular that for him, the bad guy is the parallel ...
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### Why does a multimeter put more voltage to measure a smaller resistance?

I noticed this behaviour on two different multimeters (different models and brands as well). At first I did not put a multimeter in the way to measure how much voltage changed for the different scales ...
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### how to measure the internal resistance of a voltmeter?

How to find out what is the internal resistance of a voltmeter? I imagine the higher the better - it'll have less influence on the measured circuit. What is the approximate internal resistance of ...
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### Monitoring voltage without a known reference

I'm working on a little sensor platform that runs off of batteries. I'd love to be able to trigger an alert when the voltage gets too low. The problem is that anything I use to measure that voltage ...
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### How does a non contact voltage tester work?

How does a non contact voltage tester pen detect voltages and/or currents? Are they limited to voltages of a certain range or type (AC or DC)? Here's some experiments I have conducted that lead to ...
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### Why does an oscilloscope show a different voltage from a signal generator?

I have a Rigol DS1052E oscilloscope and a Rigol DG1022 function generator. I have just changed the oscilloscope fan for a silent one, as I found, as is commonly reported, that the original fan noise ...
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### Is it feasible to measure voltage drop across 0-ohm jumper resistors to determine excessive current draw?

We design very low-power devices which in standby mode use about 8 µA of current. They are powered by 3 V lithium primary cells and are designed to last for many years. Every now and then we see a ...
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### How do I know if a wire is floating or not?

In digital logic, there's a state called "1" which is a defined high voltage, for example 2.7 V - 5.0 V. To achieve it we must connect it to VCC. And "0" which is a low voltage, ...
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### Reasons not to use these leads

I found the following note with a set of test leads we use for our Agilent 34461A[1][2]: This Test Lead Set is designed for use with the Agilent 34xxxA Multimeters, and also the U274A, U3401A, and ...
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### What's the use of the 100 kΩ resistors in this schematic?

I saw a schematic for measuring AC voltage on a 3-phase mains supply (R/Y/B are the 3 phases and N is the neutral) I understand that the 1 MΩ and 2.7 kΩ resistors are for stepping down the voltage (...
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### Arduino: Measure external voltage

I have a "problem" while trying to measure the external voltage from a coin cell. I have simplified my circuit, but basically I have a DS1307 real time clock powered by the Arduino 5v output, and a ...
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### Arduino has an input value in disconnected pin

I'm new to arduino. Maybe is an elemental question... If I load this program: ...
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### Why can't a multimeter measure its own current and voltage?

Well I finally obtained another multimeter, so now I have a Mastech MS8226T and a Ben Electronic M92A. I decided to measure at which voltages would the low battery warning appear and how much current ...
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### Help me calculate voltage drops through this circuit

Home hobbyist here, just trying to learn. I'm trying to calculate voltage drops across the various components, and I'm stuck on R4. I calculated R1 and R2 no problem (I think), using: ...
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### Is it normal for a lithium ion battery to read with a very low voltage on a multimeter?

I have a PS Vita and I suspect the battery is dead and needs replacing, as the Vita won't charge at all. But the issue could also be the charge circuit, as when plugging it in to charge the charging ...
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### Measure high voltages with a multimeter

My multimeter is rated to 600V. How can I readily (and safely) use it to measure higher voltages?
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### How can I measure battery voltage with my MCU?

I am currently using the PIC24FJ128GA010 and I am planning to use Input/Output port to connect my 4.2 V LiPo battery and to check if the voltage value doesn't go below 3.7 V. I am thinking to ...
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### How to measure Voltage & Current with a single multimeter, Simultaneously?

I have bought a cheap but neat Uni-T UT61E multimeter, which only has one display as most multimeters. For 40 Euro's I cant complain. It's on the way to me. Q.1 If I would like to measure both ...
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### Is voltage an accurate metric for testing the charge of an NiMH battery?

I regularly use rechargeable 1.2v AA NiMH batteries, and I'd like to be able to use my multimeter to test both how much charge they have when I've finished charging them, and how much charge they have ...
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### Instrumentation Amplifier - how to use it correctly

I am trying to perform some measurements based on a special technique used to detect corrosion in rebars of concrete bloc. The idea is to measure the potential difference between an electrode and the ...
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### Auto-Ranging Meter Design

I'm designing an auto-ranging voltmeter using the on-board ADC of my micro for A to D and a digital potentiometer as a programmable resistive divider to control the range. My concern is the ...
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### Can anyone suggest a voltmeter that can do the job? [closed]

I am trying to make a high voltage measurement on an industrial sputtering machine. The voltages are in the 50V to 1000V range. Right now, we're using a Fluke DMM because we need a true floating ...
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### How to read 0 -10V analog voltage with lower voltage tolerant ADCs without a voltage divider

Background Information I want to implement an ADC as an extension to a Raspberry Pi, so that it has the capability to read analog signals. I will be using the MCP3004/3008, as I got lost in the ...
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### What does the horizontal bar indicate in the DMM display?

What does the horizontal bar indicate and how to use it in my measurement?
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### How do you calculate power loss for a diode?

For example, the DSB20I15PA Schottky diode datasheet mentions a threshold voltage of 0.23V and a slope resistance of 7.2mΩ. I need to calculate the power loss at different voltages, as the battery ...
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### Are there any tricks for measuring high voltages (~1000 V) efficiently?

The simple way to measure voltages above VDD is to use a resistor divider. However, once you get into the 100s of volts these dissipate significant power. For example, one of my current designs ...
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### Measuring AC voltage without a transformer using a microcontroller

As I have no practice with AC voltages, I'm asking if the following circuit is reliable for measuring AC voltages about 110Vca and 220Vca 50Hz/60Hz. I have already made it with a small transformer. ...
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### What is the easiest way to monitor a 120v line via software?

I'm wanting to count how often a water pump turns on, how long it's on for and when it turns off for an extended period of time. My plan was just to monitor the pressure switch, which is at 120v on 1 ...
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### Peak to Peak vs. Amplitude

For a sine wave, Amplitude is the fluctuation or displacement of the wave from its mean value. Peak-to-peak (pk-pk) is the difference between the maximum positive and the maximum negative amplitudes ...
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### How does a voltmeter work?

Let's say I've got a circuit with a two-pole Thévenin equivalent that has DC voltage difference U and out-resistance Ro. What does the voltmeter do? I suppose it has an internal, very large resistance ...
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### How do I measure a voltage greater than 5 V with Arduino? [duplicate]

I want to measure a varying voltage with an Arduino and real time data plotting has to be done. But the supply voltage will be 10 V and the Arduino is not supposed to have more than 5 V. Is there a ...
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### ATTINY85 measuring internal voltage

I'm using an ATTINY85 for a portable application that uses a Lithium-ion battery; therefor I need to monitor the battery voltage so I don't kill the battery. Is there a way to go about this without ...
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### Does the 1x oscilloscope probe setting slow down MHz digital signals?

I was debugging what I thought was a weak LVDS driver fed with a 10MHz clock for hours when, out of other options, I've set my scope probes to x10 and although the signals were showing some ringing ...
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I just got my first multimeter and when I measured a 12V 1.2ah lead-acid battery I get AC 28.8V and DC 13.4V. Is this normal? In addition I tested an AA 1.5V battery and I got 2.9V (AC setting 200) ...
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### A proper way to determine correct voltage of unmarked components?

My kids have been tearing apart a number of different gadgets, from RC cars, to toys, to coffee makers. There are a variety of cool little motors and lights in these devices that we would like to use ...
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### Can I Test Bug Zapper's Voltage With Multimeter?

I have The Executioner bug zapper: Although it uses 2 AA 1.5v batteries, it also has voltage multiplier like Cockcroft–Walton generator i guess and would like to know if it is safe and would make ...
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