Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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61 votes
6 answers
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Why am I not dead after repeatedly touching a high-voltage source?

While playing with mosquito racket in my home, I unscrewed the racket and touched the 2 wires with my hands. I felt that my bones were dislocated, I got shocked, but I am not dead. My calculations ...
pankaj prasad's user avatar
55 votes
7 answers
64k views

What is the usage of Zero Ohm & MiliOhm Resistor?

I am new to PCB design and I noticed that some schematics use 0Ω or 100mΩ resistors. What is their purpose and why do we need to use them in our PCB design? Normally if we wish to probe how much ...
Dennis's user avatar
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45 votes
13 answers
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How do I measure 10,000 A DC?

What is the standard way to measure a current of about 10,000 A? DC clamp meters seem to have only scales up to 2,000 A. Edit Some background of this question: I am a high school physics ...
Julia's user avatar
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33 votes
7 answers
36k views

How do I calculate the power rating for zero-ohm resistors?

Based on my earlier question, since there supposed to be zero voltage (V=IR) drop across a 0 Ω resistor, how do we select the power rating of such a component? For example, let's say I were to ...
Dennis's user avatar
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30 votes
2 answers
18k views

What are the advantages of a shunt resistor vs. a hall effect sensor?

I'm constructing a boost converter, and I need to measure both the input current and the output current. Currents range anywhere from 25A to 200A, depending on the model. My controller is referenced ...
Stephen Collings's user avatar
22 votes
5 answers
32k views

What is the difference between burden resistor and a normal one?

I just came across the word 'Burden Resistor'. Is it any different from a normal resistor? If it is different, where can I possibly get one? Sparkfun hasn't got one listed. Any help is appreciated....
Daniel Euchar's user avatar
21 votes
3 answers
117k 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 ?
Arun M's user avatar
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19 votes
8 answers
10k views

Finding the resistance of a resistor without multimeter

So this is a trivial but frustrating issue I’ve come across. I have two 5 band resistors and I am having a hard time differentiating the tolerance band. I don’t have a multimeter on me and I don’t ...
Jake's user avatar
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19 votes
6 answers
2k views

Is there an implicit "unit of time" involved in electricity measurement? (e.g. miles per hour, kb per second, amps per ???)

I'm very new to electronics and I am going through what must be a common difficulty in grasping voltage, current, and resistance. I'll restrict my question to current as I suspect understanding that ...
Cliff Pruitt's user avatar
17 votes
2 answers
2k views

Seven-segment display seems to draw little current

I bought a 1.8-inch seven-segment common cathode LED display from AliExpress. So no datasheet available. I used a 1 kΩ resistor and a 5 V source, as to put a max 5 mA in the LED. I measured 1.6&...
mathieu's user avatar
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16 votes
6 answers
26k views

How to plot current in ngspice?

I wish to plot out the current and power in ngspice. In the case of voltage, for example, if I wanted to plot the voltage at node 1 I would use: plot v(1) ...
sj755's user avatar
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16 votes
1 answer
2k views

Why use an input resistor in this current sense circuit?

In the Linear Technology AN 105 on current sensing one can find the following circuit. I am wondering what the purpose of the 200 ohm resistor on the inverting input is. It appears to have no effect. ...
Max's user avatar
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15 votes
4 answers
1k views

Why would a current measurement shunt design use 4 sense pins?

I am interested in low resistance shunts (tens / hundreds of microohms range) used in high voltage / high current setting. Typically, those are busbar-mounted shunt resistors like this one: The ...
Dainius Stankevicius's user avatar
15 votes
2 answers
8k views

Why don't hall effect current sensors exist for low currents?

There do not seem to be hall effect current senors available for small currents, say on the order of 500mA. I'm guessing this is due to some technical or physical limitation. What is it?
Phil Frost's user avatar
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14 votes
15 answers
6k views

How to measure small, spiky amounts of current?

Let's assume I have a microcontroller with some amount of peripherals attached and would like to be able to make a reasonable estimate of battery life. Because I might have it sleep at times, and ...
David's user avatar
  • 561
14 votes
5 answers
11k views

How to Measure Power Consumption on Extremely Low Power Devices?

This might be old news in a half a decade or two but by today's means, I am referring to electronic prototypes and designs which would draw in a μA (uA) and even nA range of current. Some recent MCUs,...
Mehrad's user avatar
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14 votes
2 answers
12k views

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 ...
Dakatine's user avatar
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13 votes
8 answers
3k views

Measure wide range of current 800 µA - 1.5 A

I am having difficulty measuring current into an IoT device that I am making. I need to be able to gather data about power consumption over time, and about the sleep mode current. I was trying to use ...
Reid's user avatar
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13 votes
5 answers
8k views

Ways to measure current in picoamperes

I need to check the low power consumption of a microcontroller in the range of picoamperes. I only have a multimeter capable of measuring milliamperes and as such it shows 0. Is there an easy and ...
Tedi's user avatar
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13 votes
4 answers
3k views

Why are current probes so expensive?

I notice that clamp-type current meters range in price from a few dozen dollars to a few hundred, but current probes for oscilloscopes cost significantly more, with many close to $1000 and some well ...
Caleb's user avatar
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12 votes
9 answers
7k views

In which scenarios is it important to measure microampere?

With the situation of finding a new multimeter, I found myself lost to the number of available devices on the market. For sure, to find the most suitable device I have to set some requirements. While ...
Toby N.'s user avatar
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12 votes
5 answers
9k views

What is the difference between high precision resistors and current sense resistors

Actually, I am trying to build a current monitor for a wireless sensor network. I am going to use a current sense resistor as the current will pass through the resistor. By measuring the value of the ...
Sabir Moglad's user avatar
12 votes
4 answers
35k 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 ...
JWVincent's user avatar
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12 votes
2 answers
4k views

Measuring average current with uC and current shunt

This is my first post. I'm a software guy trying to do hardware so be gentle :) Circuit I'm designing a small circuit (see pic, and sorry for messy schematic) that plain and simply is a bunch of ...
ltj's user avatar
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11 votes
8 answers
14k views

*Very* high precision, *very* stable current source

My background: experimental physics. Not an electrical engineer, but I have some experience putting together basic electronic circuits for physics experiments. So please be kind and explain as if I'm ...
ugachmaaz's user avatar
  • 127
11 votes
4 answers
7k views

Is current flowing backwards a bad thing?

In the circuit below: I find it awkward that the direction of the current on the 2V power supply is running opposite to the direction of the current on the 5V power supply. In the 5V power supply the ...
T555's user avatar
  • 1,599
11 votes
9 answers
2k views

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 ...
JYelton's user avatar
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11 votes
3 answers
2k views

Why does a 50 Hz, 200 mV sine wave appear sometimes on my portable oscilloscope without a probe connected to anything?

I have a portable oscilloscope, and when I connect just one probe to it, sometimes, moving the probe into the air without connecting it to anything, then I can see (in some of the places of my house) ...
Roger's user avatar
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11 votes
2 answers
836 views

Do batteries last longer with constant current draw or spiky current draw?

Do batteries last longer with constant current draw or spiky current draw? Or, as is implied by the accepted answer to "Making a battery last a long time in a microcontroller circuit", do some ...
davidcary's user avatar
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10 votes
4 answers
3k views

Why does a brushed DC motor current draw differ with direction of rotation?

I was trying to test the capacity of a battery pack I'm building and was trying to measure the current draw using a 35 turn 540 brushed DC motor (the website I had purchased from said something about ...
The_Vintage_Collector's user avatar
10 votes
2 answers
2k views

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 ...
Mast's user avatar
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10 votes
3 answers
2k views

How OPA333 withstand 400V bus without burning in this current sensing application?

I went through following app note, where OPA333 is used in 400V bus current sensing application, also i have seen current sensor which have term called common mode voltage, which is specify the max ...
kobi89's user avatar
  • 194
10 votes
3 answers
1k views

Amplifying High Voltage nA Current

I have a circuit that is essentially just a 1kV DC source connected to a very high resistance (basic circuit outline), within which current in the range from 0.1nA to 500uA flows that I am trying to ...
Jack's user avatar
  • 211
10 votes
1 answer
7k views

Transistor current mirror circuit

simulate this circuit – Schematic created using CircuitLab Can somebody please explain me how a transistor mirror circuit works and how can it be used as over current detector? I badly need a ...
IamDp's user avatar
  • 1,885
9 votes
6 answers
2k views

Do you have to use an instrumentation amplifier to measure voltage across a 0.01 ohm shunt?

I was planning on implementing a current sense feature on the STM32 Bluepill to measure the current output of a solar panel (150 mA short-circuit current, 14 V Open-circuit voltage) using LM358 ...
A.H.Z's user avatar
  • 633
9 votes
4 answers
3k views

How to detect high current

I am working on the project which involves running a DC motor which is used to raise/lower window glass in the vehicle. While running, motor draws about 1.5A of current. However, when the window ...
Nikola Malešević's user avatar
9 votes
8 answers
1k views

Measuring the activation time of a solenoid

I'm trying to measure the activation time of a pull-type solenoid. When the solenoid doesn't have a load connected to it, you can measure its activation time through the current it consumes. At first,...
Florian Humblot's user avatar
9 votes
2 answers
951 views

Bad Measuring Equipment?

I was measuring the current through current mirror, when I experienced a problem. But first, I want to mention that I measured this with two ammeters of same manufacturer and same model (Mustool MT826 ...
lucenzo97's user avatar
  • 2,430
9 votes
4 answers
4k views

Sensing DC motor current

I am allowing the current through a DC motor to flow through a small resistor and measuring the voltage across it. I need to give this analog Voltage to an ADC of micro-controller to do some signal ...
Aashish Thite's user avatar
9 votes
1 answer
3k views

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 ...
AndrejaKo's user avatar
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9 votes
3 answers
2k views

Short time-scale coulomb counting

There exist many coulomb-counter chips which measure the integrated current going into or out of a battery for purposes of estimating the charge state. Are there any good chips for easy circuits for ...
supercat's user avatar
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9 votes
2 answers
609 views

Why do some of my IE converter circuits have a large offset voltage?

The following circuit is an active current to voltage converter with switchable gain. Schematic Not shown: The inverting input is held low through a 10K resistor when the circuit is powered on but ...
Steven T. Snyder's user avatar
8 votes
11 answers
3k views

Easy and cheap way to sink more than 5 A from a power supply

For an experiment I need to check a current sensor but I need to parallel too many resistors to achieve that without damaging the resistors. I don't want to do that. The PSU is 12 VDC, 10 A and I want ...
cm64's user avatar
  • 2,141
8 votes
3 answers
2k views

Why is my circuit's current far lower than expected with 2.6v / 220Ohm / and LED?

I have a very simple circuit which I have measured the current to be only 3mA but should be in the range of 18mA. I have a simple circuit using 2 AA batteries (NiMH) at 1.3V each in series for a total ...
raddevus's user avatar
  • 1,252
8 votes
4 answers
1k views

How to design a circuit to measure really small currents (nanoamperes for example)?

I have to design an analog circuit to measure currents in the nano ampere range as part of a course, and from what I found on Wikipedia and some documentation available online from Tektronix, it seems ...
Koustubh Jain's user avatar
8 votes
2 answers
12k views

Why does an ideal capacitor give rise to a rectangular cyclic voltammogram (CV)?

Many scientists are interested in developing supercapacitors, which have electrolyte rather than solid dielectric between the charged plates. In the field of electrochemistry, cyclic voltammetry (CV) ...
Andrew's user avatar
  • 175
8 votes
4 answers
8k views

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 ...
Sam's user avatar
  • 515
8 votes
1 answer
4k views

Using a Shunt Resistor to measure current

Usually when we measure current, we have to break the circuit and place the ammeter in series. However, if we want to make it easy to measure current at various points in a permanent circuit(for ...
Ammar's user avatar
  • 491
8 votes
2 answers
27k views

How to measure max current of a power supply

I have a 220V to 12V adapter. According to the adapter label, the max current can reach 1.5A. But I want to measure the max current it can reach without depending on the information written on the ...
Wuthian's user avatar
  • 257
8 votes
2 answers
2k views

Under what conditions would using a voltmeter be more accurate than an ammeter to measure current?

Suppose you have a simple circuit with a voltage source V1 connected to a resistor R1, like this: simulate this circuit – Schematic created using CircuitLab You could connect an ammeter in ...
kieransquared's user avatar

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