# Questions tagged [voltage-measurement]

Act of measuring voltage

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### What's the most economical way to digitally measure 240V mains voltage, current and power factor?

I'm looking to capture and analyse measurements of the mains energy that I use per circuit. I've found a few consumer products that offer powerpoint energy monitoring such as the Kill-A-Watt, but PC ...
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9k views

### 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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1 vote
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### How to improve resolution and presicion of sensor reading?

I'm trying to measure temperature with an arduino uno and a LM335 temperature sensor. The LM335 can provide differences in temperature between -40C to 100 with a resolution of 10mV. I read the sensor ...
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235k views

### 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 ...
25k views

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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24k views

### 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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111k views

### 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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### ADC for measuring 0-5V but connected to 3.3V device

I have a BeagleBone (BB) and want to connect the analog output of a motor controller to it. The motor controller creates an output in the range of -4V to +4V and the BB anlog inputs only accept ...
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32k views

### 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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9k views

### 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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12k views

### 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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4k views

### Measuring Battery Voltage from Microcontroller using ADC

I am currently using a PIC16f1826 to try and measure the voltage of the 3.7v battery that is powering said microcontroller. From my understanding, the ADC can measure from 0v up to the reference ...
7k views

### What is the voltage drop across the 10 ohm resistor?

What is the voltage drop (V1) across the 10 ohm resistor? Can I use voltage division to get V1? Like V1 = (20 V x 10 Ω) / (10 Ω + 4 Ω) But when I use nodal analysis and mesh analysis I get a different ...
551 views

### Trying to understand prescaling voltage for ADC with least error

I'm teaching myself EE while designing a 12V DC battery monitor. I'm using a pair of Hall-effect sensors to track charge & load current and looking for the best way to measure the voltage. [An ...
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12k views

### What does the moving iron voltmeter measure in a circuit, average voltage or RMS voltage?

What does the moving iron voltmeter measure in a circuit, average voltage, $V_{average}$, or RMS voltage, $V_{rms}$? $V_{average}=\frac{1}{T}{\int_{0}^{T}vdt}$ \\$V_{rms}=\sqrt{\frac{1}{T}\...
• 53
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2k views

### resistor value in wheatstone bridge

I have a resistance based sensor which gives the resistance change when the strain/force is applied. How to measure the unknown resistance change using the Wheatstone bridge circuit.? I mean what are ...
107 views

### Ambiguity in voltage measurement

So I watched this extremely fundamental video about voltage measurement and how it's measured. The one thing that confuses me is what people use a reference for zero potential. The two diagrams shown ...
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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 ...
• 2,242
14k views

### 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 ...
67k views

### 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 ...
• 1,915
52k views

### 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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### 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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### Isolated voltage and current measurement

I'm designing a safety shutoff circuit that monitors several power supplies, both voltage (12V, 24V, 72V) and current (up to 8A). These are entirely independent supplies, so I'd rather not tie the ...
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821 views

### 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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2k views

### Measurement of negative DC voltage

I want to measure -30Vdc up to 0Vdc using a microcontroller. I'm basically measuring a voltage source with an output current of upto 2A. I need to bring the voltage up onto a scale of 0V to 5V so ...
• 157
10k views

### 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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30k views

### 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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18k views

### How to measure mains AC voltage with an ADC from a microcontroller?

I want to measure the Mains voltage (230V/50Hz) using an ADC channel from a microcontroller. This is my current approach ... Below I have two schematics that add two voltages (one direct, one ...
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339 views

### How can I do two points scaling in electronics? 0.6 V - 3.2 V to 0.0 V - 3.3 V

I'm seeking a solution how to do a two point scaling in electronics. I have tried an Op-amp, but it did not work very well. So I wonder if you have some ideas how to do two point scaling from e.g 0.6 ...
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### Measuring noisy signals: Does wrapping the test lead through a ferrite reduce common-mode noise?

Let's assume we have a test set-up involving an oscilloscope and a unit we are testing. we measure the voltage between two points using a standard scope lead and see significant noise, I now take out ...
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726 views

### AC Power measureless using MCU, calculations problems

I'm done from the hardware design sensing the current & the voltage levels using my MCU (AVR) & some circuitry Beside I wrote the firmware to handle the ADC data & so on But I'm, having ...
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### 1000 watts, 220 volt, 52" length, Coiled Nichrome wire

I need to use Nichrome wire for heating purposes. My heating temperature could be among 200 Celsius, voltage should be 220V, wattage should be approximately 1000 Watts, and length should be 52 inches ...
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### How to measure voltage in a PS/2 keyboard cable?

I have an old PS/2 keyboard, I doing a future project with it, but for now I just want to measure the voltage in the cable. However I don't know how to do it, so let me explain. It's a PS/2 keyboard, ...
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429 views

### Designing a battery capacity monitoring system for AGM lead acid battery

I would like to design a battery capacity system for my AGM lead acid battery (12v, 40Ah). My idea is that I have values of the battery voltage and its corresponding capacity, which I will use to plot ...
1k views

### Protecting against over voltage but with minimum leakage current

I have a circuit where I sense an input which is a voltage divider with resistor. Since the voltage divider needs to have high impedance, the current flowing through is in the range of 10's of uA. I ...
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### Differential high voltage measurement using a transformer

I have questions about the limitations of using a mains-rated power transformer (e.g. a small 6VAC 1VA PCB mount transformer) as a cheap differential probe, so that waveforms can be safely observed on ...
2k views

### XBee and PIR sensor

I've ordered XBee wireless transceiver and PIR (motion, here is link) sensor. When I enable DIO0 digital input port on XBee with "ATD0 3" command it becomes high. I measure it with volmeter and get ...
1k views

### How can I calibrate my sound card based oscilloscope?

I'm using Soundcard Oscilloscope software that presents as below You'll notice that the display has a grid, and in the example is set for 100mV/div. Since it's using the sound card integral to my ...
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### Computer line-in voltmeter

I'm about to make a voltmeter from computer line-in. In some strange way I can not see direct current from computer. Why does it work only with alternating current? What information does captured wave ...
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### What's the low voltage displayed by a voltmeter when only one of its probes is connected?

Recently I was toying with a digital multimeter and observed the following. The multimeter was set to measuring AC voltage with the upper limit of 750 volts. It has two probes which I will call "red" ...
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### How To Detect If Two Voltages Are The Same And Trigger An Output If They Are

Basically, I'm struggling to design a circuit with the following requirements: Requirement 1: Output is high (say 5v) when the two input voltages are different. [If it makes it any easier the output ...
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197 views

### How can one use the earth as a second wire?

I read recently that the earth can be used as a wire to save wiring costs. My understanding of how this works is that a power source, say a battery, separates charge, creating electrons on one side ...
175 views

### How to measure voltage of each bank in a Marx Generator?

If I have a 10 stage Marx generator with each stage at 2.5kV, when I erect all the stages the last stage's negative terminal will be at 22.5kV with respect to ground. If I want a voltage ...
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### Ungenerated Voltage across the DMM and random spikes across the Oscilloscope

I am working with piezoelectric material known as PZT-P-43 MY PZT datasheet (please look at the red outlined). So far I have been trying to find the Energy that is being delivered to my 100uF ...
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### Converting variable capacitance value to variable DC voltage level

I need a simple method to convert a small variable capacitance value into considerable variable DC voltage. Capacitance value range = 0nF ~ 14nF DC value range needed = 0V ~ 6V What I've tried is ...
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### How can i measure voltages on each phases of a 3 phase system, Using a microcontoller?

How can i measure voltages on each phases of a 3 phase system. The measurement is to be processed by a microcontroller. Is there any special chips available, or do i need to use the ordinary ...
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### Detect one out of five distinct voltage levels

I got a fan on my roof which is powered via a five step manual transformer to control the speed. The transformer outputs a voltage of either 0, 90, 110, 135, 165 or 230V AC. I would like to use an ...
519 views

### High precision resistance meter

I'm designing a high precision resistance meter, which will measure the change of resistance of a given remote resistor, which is not placed on the circuit PCB, against temperature. I want to do this ...
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### When measuring AC via an ADC, is it bad to have common ground?

I've got a circuit that looks like this: circuit http://img.skitch.com/20111127-m6jqyx9b15brese4rkipayyib6.png My input is low voltage AC at low current and I want to measure this with an ADC at 3....
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