Act of measuring voltage

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Question about Battery Charging and Voltages [on hold]

There’s a Lead-Acid rechargeable battery 6V 4.5Ah in an emergency light device. Battery specs say Cycle Use 7.2 – 7.5V Standby 6.75 – 6.9V. I got some idea about what these values mean here. Its ...
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33 views

Battery voltage isolated monitoring on Microcontroller

Is it safe to directly measure high capacity battery (100 Ah to 300 Ah) voltage with Microcontroller's Analog to Digital Converter (ADC)? Would it be enough to use just a simple voltage divider to do ...
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3answers
83 views

Battery voltage select and ADC measurement (OpAmp + uC)

I need to measure battery voltage which supplies my electronics. Vbat supplies buck-boost DC/DC converter then goes to uC and other ICs (3,3V). I want to use 3x2 goldpins in conjunction with OpAmp to ...
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2answers
91 views

Can I measure if current is on or off in cable with 24v DC (in a cheap way)

I have a number of valves that control the heating in rooms in our house. The valves have a pin on top which opens or closes the valve. The position of the pin is controlled by a regulator that sits ...
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43 views

what is the base temperature when using ppm/c

I am not sure If I have phrased the question right but if not please correct me I want to know when Accuracy Parts per Million mentioned in the datasheet of voltage reference they say for example 5 ...
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1answer
48 views

VGA levels, why are they wrong?

I read everywhere on the Internet that voltage levels in the color components of a VGA cable should go from 0 V (dark channel) to 0.7 V (maximum brightness for that channel). However I tried to ...
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3answers
71 views

Correct way to measure a wall wart voltage [duplicate]

I got a full drawer of second hand wall warts which I'm planning to use for powering arduino projects (mostly 5V "pro mini" or "nano"). I'm using a voltmeter to check that they are still working, ...
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201 views

Is voltage measurement of a battery done in series?

This might be a stupid question but I can't find an explanation. Voltage measurement is done in parallel. But when we measure the voltage of a stand alone voltage source, say a battery, it looks like ...
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51 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 ...
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56 views

Measure Voltage (Divide) on a current source

I need to use a constant current source 20mA, the current flows through multiple diodes and resistors which are in series. The resistor value can vary from 0 to 1.6k and also a possibility of Open. ...
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111 views

A DC micro-voltmeter

Basically I will be calibrating circuits to a high degree of precision. Keeping it minimalistic, I figure all I needed for that are resistor networks, voltmeters and a few high precision voltage ...
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65 views

continuous battery monitoring during charging as well as discharging

My application is basically a power monitoring system in which inverter voltage(RMS),current(RMS) and battery voltage,current are measured. 24V battery is being used in the application. I am using ...
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84 views

Measure resistance value between all nodes in a 3x3 resistor grid

I have a Schematic like that: (except the power supply is an Arduino Uno with a voltage divider to measure resistance between any pair of ABC and 123, except C3 of course) How can I get the ...
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2answers
30 views

Type of Wideband Transformer for Measuring 120 V AC signal + EMI

I'm looking to measure line EMI on a standard 120 V AC power circuit using some kind of transformer or other sensor. The device I'll be using to measure the waveform is an Ettus Research USRP N210, ...
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1answer
115 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 ...
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158 views

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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79 views

Increase voltage of signal by 0.6V

I am trying to fix a voltage drop issue. The cable I am using has a voltage drop of around 0.6 V this is then fed into a charger signal input and because of this drop it does not see the alternator ...
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43 views

Old 9v battery - Strange Behavior

The battery in my garage door remote finally quit. Before replacing it, I measured the voltage with a digital multimeter and was surprised to find it reading 9.70v, quite a bit higher than the ...
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84 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 ...
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1answer
65 views

Measuring the amplitude of a sine wave

I want to measure the amplitude of a sine current signal (about 1kHz). The signal is of small amplitude, i.e. smaller than 50 mA. I suppose a simple rectifier is not accurate enough or even doesn't. ...
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2answers
98 views

Accurate RF voltage magnitude measurement

How would you measure the magnitude of a RF sinewave in the KV, MHz ballpark? The frequency is known and the sinewave is very pure, does this help? Can you devise a method that would give ...
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87 views

Why does DMM resistance measurement not settle when probing pins on circuit?

I am probing two pins on a custom circuit board which I believe have been shorted somewhere and am attempting to measure the resistance between these pins with an Agilent 34401A multimeter. When ...
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79 views

When to read Battery voltage and battery current during charging

I am using a micro-controller to drive a buck converter for Li-ion battery charging purpose(Micro-controller providing PWM to the buck converter). During charging the battery's current and voltage ...
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121 views

How do security alarm systems measure zone resistance?

Recent security alarm systems use EOL(R) or DEOL(R) to terminate the line of the zones. Question 1: What method is used to measure the resistance of a zone? I can think of two options: It measures ...
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1answer
48 views

High voltage to low voltage conversion from multiple channels

There are more than 200 lines and every line carries voltages in the range of 0-36V.What are all the possible ways to convert 0-36V (pwm signal,5kHz) to 0-5V for ADC input? Note: I should not ...
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1answer
82 views

Non-contact mains voltage measurement

I am trying to develop a non-contact whole-house power usage monitor. I have reviewed jasonT's project, which uses AC clamps to measure current usage. However, from reading this post on how meters ...
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81 views

Op-amp - dual to Single supply conversion to avoid floating of input signal?

I'm designing a voltage measurement adaptor. And my signals are PWM type which ranges from 0-36V. I thought of using Op-amp to step down to 0-5V range and use an ADC to convert analog signals into ...
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198 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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24 views

Measuring and classify stepper motor

Hi guys I've got a little projet running and need your help: I am going to use a stepper motor and a motor driver, in my mind that should work (maybe with a heat sink for the driver). What do you ...
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1answer
50 views

Correct way to choose resistors for load

I've come across two ways to determine which resistor value is needed for a load. The first one, which is always titled 'How to determine resistor value for an LED' says that you can use the formula: ...
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1answer
53 views

Strange behaviour of real log amp

I'm facing some problems with my log amp circuit. My configuration is this: http://i.stack.imgur.com/nrF12.png and the "gain" function in case of ideal op-amp is: V_out = -V_t log(V_in/R1 I_es) with ...
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1answer
71 views

Measuring battery voltage and saving energy [duplicate]

We have a pcb with an Atmega (MCU) on it, that most of the time is in sleep mode, consuming 50-100 uA . When it wakes up, and only then , we need to take a sample ...
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128 views

Three-wire Voltmeter [closed]

I have a boat with a dual battery system and have purchased two 0-30V voltmeters similar to this one, it has three wires which I understand is negative, positive and a wire for the voltage to be ...
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99 views

Voltage Regulation

I am a young engineer and I need a help from you. I need to design a driver circuit which must power-up a LED (OC) if the measured volatge is greater that 50V (Voltage to be measured can be upto ...
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2answers
65 views

Efficiently sensing the voltage of a battery pack

I'm looking to sense the voltage of a battery pack that is powering a device by the device. Depending the the level of the pack (2 cell LiPo 1200mAh) the device will change it's behavior. As the pack ...
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1answer
100 views

Is it possible to measure the voltage produced in heart

I learnt from my high school biology that human heart will produce about 1mV from the sinoatrial node.(voltage will vary like the graph in ECG test).Is it possible to measure the voltage with any ...
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61 views

Dual integrating ADC to interface with micro-controller?

I would like to measure voltage with an IC similar to the 7106 but I don't want all of the 7 segment display circuitry that it comes with. I just want to interface it to a micro so I can perform other ...
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63 views

Instrumentation Amplifier output mysteriously increases upon connecting across a resistor, compared to connecting the same voltage directly across it

I am designing a simple resistance measurement circuit. Resistance range is from \$10m\Omega\$ to \$10k\Omega\$ and desired accuracy is 0.1%. The circuit provides constant current to the resistance ...
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142 views

RMS OR DC value of the waveform is measured by DC voltmeter for the below input?

The DC voltmeter measures the average value of the waveform right? I have read that ac voltmeters (high end) measure the RMS value based on heating effect while DC voltmeters measure the average ...
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104 views

Clarification about AC and DC coupling on oscilloscope

I was measuring voltage on zener diode and found unclear behavior of oscilloscope. So I have function generator which puts saw wave(or sine, doesn't matter) of 20 Vpp. It goes through 1k resistor to ...
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54 views

fast current pulse

I am wondering if there a way to convert a pulse train with a 200 kHz rep rate, a duration of ~100 nanoseconds, and an amplitude of ~4 volts to a DC voltage in such a way that the area under the ...
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3answers
98 views

What values for current and voltage are considered “relatively small” or “relatively large”?

Background I am working with a Yokogawa WT310 power analyzer. A section of their getting started guide, available here, has this diagram: I understand the purpose of these diagrams, and they make ...
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144 views

Using a Piezo sensor to detect audio frequency

I recently posted here without much success on this subject but I've moved forward a bit and got stuck, again! I have Raspberry Pi and a MCP3002 ADC chip because RPi doesn't have any analog pins. I ...
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2answers
260 views

Under which possible conditions is measuring with an multimeter a danger to life ?

My knowledge of electrics is very limited, I am planning to buy a Multimeter, but I am confused when it comes to safety. I do not really know what is a danger to life when measuring a circuit with a ...
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44 views

Determining the input voltage range of an adaptor [closed]

The label of a power adaptor is damaged so no information if the input voltage is 110V only or 100-240V range. The output is 500mA at 5.5V. I would like to use the adaptor in a 220V country. How ...
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1answer
81 views

More voltage than supplied

I stripped the ends of a 14v DC power supply to power a small 6-12v DC motor. I first measured the voltage coming from the supply and found an actual 17 volts coming out, but then when I connect the ...
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2answers
179 views

How can I calculate DC motor continuous current?

I have some information for a brushed DC motor: ...
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54 views

Strange frequency of audio output voltage

For a school science experiment, we have stripped an audio cable and hooked the right channel and ground wires up to a voltage graphing device. The audio cable is plugged into the audio output of our ...
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2answers
133 views

Why we want to convert a voltmeter to an ammeter or vice versa?

Why in laboratory experiments do we want to convert a voltmeter to an ammeter and vice versa? What is our main aim here that is for what we are doing it? If our goal was to change the range of the ...
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2answers
135 views

Getting negative voltage reading when negative voltage does not exist. Why?

I am beginner trying to make sense of some weird voltage readings I am getting. Please take a minute to look at the circuit below: If I take my oscilloscope and capture the voltage activity across ...