Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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Measuring power consumption of Wiimote adapter not working, what am I doing wrong?

When I try to measure the power consumption of various Wiimote accessories, the multimeter only says 0.0mA, so I wonder if I'm doing it wrong. Here's how I measure: A more detailed explanation: ...
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26 views

Input leakage current affect on CMOS multiplexer ( TMUX1208 )

I am working on a board that operates with the current range up to pico ampere, I am looking to include a mux to provide multiplexing (8:1 multiplexer) between the sensor and the MCU within this ...
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2answers
86 views

How to do i solve this electrical circuit?

I've been trying to solve this circuit with two current sources: Following is given: ia = 1mA, ib = 2mA R1 = 1K, R2 = 0.5K, R3 = 2.2K, R = 4.7K Personally I've been trying to use KCL to determine ...
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63 views

how to interpret this scale?

I have been taking current lectures, but I'm confused about how must be taking the reads, using the scale selector as show next there is 310 number, but this are 310mA? I almost never take current....
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18 views

Understanding IMON and PMON in LT2940

I have two 12 bit ADC-channels that I am suppose to use in order to read measurement pins in lt2940: Imon Pmon To make it easy, I have 16 Vin and want to scale the input so that I can calculate the ...
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1answer
42 views

High side current sensing using differential amplifier

I would like to measure current making use of a shunt. Since the solution needs to be scalable I wanted to have a circuit that would be easily adjustable to various current ranges, and therefor opted ...
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3answers
47 views

Controlling cardreader numpad input with microcontroller

I am trying to automatically input a pin code into an electronic card reader so I can automate the process. First thought was to build a small robot finger and control that to input the code, ...
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19 views

Why this switch's current sense ratio sometimes increases and sometimes decreases?

The Infineon BTS50055-1TMA is a "smart" power switch that is basically a FET with current monitoring. The equation for calculating current is given by the first entry in the truth table on datasheet ...
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17 views

How to determine the minimum current a Core-Balance CT can sense?

I have a core balance CT with these specs: 950 +/- 15 turns of #39 AWG mV output test: 30 mA (60 Hz) through one turn primary with a 1K resistor across secondary winding should give an output ...
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1answer
143 views

Should a grounded case have voltage across it?

Ok so simple question though it might seem stupid. I'm wiring up a simple metal enclosure with a control unit inside. AC current from the wall, 240v~ to the unit. I'm containing it in a metal case ...
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1answer
62 views

Non-invasive Low Current Measurement

I've been tasked with non-invasively measuring a 200 mA pulse signal through a wire. The solutions that come to mind are using a current clamp or a hall effect sensor. I don't need an accurate reading,...
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83 views

Multimeter can't measure current. Maybe broken?

So basically when I put red jack to 10A mode it shows amperage fine, but when I switch to other, it shows 00.0 eveywhere, even when I set to micro amperage it doesn't react to my tongue and skin. It ...
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46 views

ACS712 current measurement not working

I have ACS712ELCTR-20A-T and I have connected it with the 5 Volt/10A converter. Vout in the schematic diagram above, is connected to ...
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2answers
76 views

confusing multi meter scale

In testing for a parasitic drain in my truck with this meter in ammeter mode, I realized the scale of the amp reading is ambiguous in that the reading does not change with the decimal point. This ...
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1answer
45 views

How to sense a small current while handling larger ones

For one of the projects I'm working on, I need to monitor a DC power line for reverse current; the solution has to output a 24V signal when around 10A or more of current is flowing in reverse through ...
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3answers
96 views

Can a multimeter really accurately measure the output current of a SMPS?

Most multimeters are bandwidth-limited to below 1khz while the current ripple of most SMPS is well above that. Even benchtop multimeters usually have bandwidth up to ~300kHz, which is not enough to ...
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1answer
38 views

Understanding Power/Current/Voltage drawn by LED Strips

I am trying to create a LED lamp which will be powered up by a battery. Lets assume I want it to run the lamp for 1hr. My LED Strips operate at 12V with 19.2W/M. I am using around 1.7 Meters(198 LEDs) ...
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208 views

large voltage spike over shunt resistor even at no load

I'm trying to build a stepper-motor driver. Each windig is driven as shown: at the moment, im feeding this with PWNM signals of constant duty cycle, just to see how everything response. (PWMs are ...
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38 views

Phase and Gain of transimpedance amplifier and effect of input impedance

I am new to hardware design. I am designing measurement circuit for Impedance Spectroscopy of electrochemistry cell. I need to measure the current coming from electrodes which have range from few ...
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1answer
133 views

Dave Jones' uCurrent Gold - trace to shunt resistors has no soldermask

I was going through the uCurrent project and noticed something that seemed unusual to me. In the image, the trace connecting R1 to the input jack is (a) of differing trace widths, and (b) has no ...
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1answer
72 views

Arduino current measurement

Hello I am planning to use an Arduino to make a joulemeter for a current range of 0-30 amps and voltage range of 0-24V. The voltage measurement is fine but I have questions about current measurement. ...
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2answers
73 views

Measurement current consumption of low power circuit [duplicate]

I have a circuit which has uC, Bluetooth module and some other ICs. Current consumption of it varies between 100uA and 20mA. I want to see current waveform using oscilloscope. I worked before high ...
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4answers
89 views

Alternating voltages on vintage calculator circuit board

I am an electronics novice. I have a vintage calculator with six secondary wires coming out of its transformer and ending on the board, as shown below: Using the AC portion of the multimeter, I ...
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1answer
54 views

Is ferrite correct material to use for a DC current sensing application

I am trying to build a non-invasive current sensor using a hall effect sensor and ferrite core. I am using a hall effect sensor sandwiched between 2 halves of a ferrite core like this: ferrite core -...
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1answer
47 views

Current Transformer noise in idle state

[ *Violet is the bias voltage. Yellow is the CT output. You can see it drifting from bias volt a little. * I want to build a power measurement circuit using STM32F407. I am using LM324N opamp for the ...
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69 views

Voltage and Current Sensor for Alternating Current

I want to measure the voltage and current of a AC powered device using a micro controller like Arduino. I am unable to find it.(I am new to these). Is there a circuit or sensor which isolates from the ...
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2answers
54 views

How to find I(t)?

so I'm trying to find the current I(t) passing through the node above the switch. I have already found the DC response of the RC circuit which is in the form of: so, after the switch closes a short ...
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151 views

Impulse response function single coil

How can I measure the impulse response function of a single coil - like an electromagnetic shaker? The construction of a second winding would be difficult. I was thinking about a T/R switch but there ...
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1answer
68 views

How to measure amplitude MHz sine wave with 50 volts common mode

For a resonant switching power application I need to measure the amplitude of a differential signal that is a sine wave with frequency between 1 and 2 MHz, and amplitude up to about 2 volts. There is ...
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1answer
31 views

Can an INA219 current sensor operate with a FET body diode present over the sensing pins?

I'm designing a board with optional current sensing modules (based on INA219) that can be plugged into it for monitoring the current on some 12V lines that go to peripheral devices. The schematic for ...
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2answers
72 views

Motor stall detector with a voltage divider in parallel to the motor and ADC: it does not work as expected

I'm trying to replicate a motor stall detector I found on a PCB of a commercial device (chinese). This is the schematic: I'm using an ESP8266, resistors with same value as in schematic, two MMBT3906 ...
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2answers
67 views

Connecting a low-side gate driver to a FET with current sense resistor

When connecting a low-side FET gate-driver to a FET (N-channel MOSFET) that has a current sense resistor connected between its source and ground, where should I connect the ground of the gate driver? ...
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1answer
320 views

Can I measure current with a 0.1Ω shunt?

I am currently trying to make a game console out of a Raspberry Pi 4 and a hard drive, with an Arduino to control boot, shutdown or reset, plus temperature. I got a degree in engineering in ...
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92 views

Is Inductor peak current same as the Inductor Inrush current

I am using a DC-DC converter which is having an inductor rating of 68uH and 2.05A. Output Voltage of dc-dc is 23V and output current max is 300mA Schematic : I am using a current probe and ...
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1answer
64 views

Why does this USB device draw different currents from different sources?

What would cause a USB device to draw drastically different amounts of current, but still function properly? Background & Research: I purchased a Playstation 2 Graphics port->HDMI converter (...
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34 views

Interfacing CT signal to Arduino

I want to interface the following CT to Arduino: So I have the following data: Primary Current: 600 Arms Secondary current: 5 Arms Burden: 2 VA Burden = 2 VA means that: Rmax = P/I^2 = 2/25 = 0.08 ...
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1answer
53 views

Ammeter with 2 voltage sources without superposition

I'm studying for the exam of this very basic circuit analysis class that I'm taking, and there is this particular problem in the textbook: You are supposed to solve this without using the ...
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1answer
77 views

Understanding low current measurement

I'm trying to understand a current measurement of a hobby project. This project consists of several ICs and is battery operated. At a certain mode (deep sleep) it should consume a very low current, ...
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27 views

How to calculate the maximum current that a wire can handle? [duplicate]

What are the methods that manufactures used to do so ? What is the formula used if there is a one to do so?
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1answer
83 views

Problem with high-side current measurement

I am having strange failures in a high-side current measurement circuit that I have not yet understood. The U3 measurement chip is getting damaged and shorts out. Perhaps someone can help identify ...
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55 views

Measuring just half the sine wave of a current measuring transformer?

I'd like to measure current of electrical devices using one of those split-core transformers you clip around an AC wire, which has a built in shunt resistor and hence outputs a voltage. I'd like to to ...
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1answer
62 views

Detecting low currents in high current industrial environment

I would like to detect if a current flows in a 3-phase industrial environment where currents can go up to 120A. Anyway, for me is only important information current is flowing/current is not flowing. ...
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4answers
2k views

Measuring voltage across 1 ohm resistor

This might be a very stupid question, but I can't seem to figure this out and I'm going nuts thinking about it. Assuming you are trying to adjust the fixed bias of a tetrode push pull pair in a tube ...
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1answer
124 views

Current measurement opamp, is this circuit flawed? Output all over the place

This is a circuit to measure a current flow that is 0-10A DC. The output goes to an ADC. The circuit itself works fine, however, over a dozen cards, the output of this circuit is all over the place. ...
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77 views

Measuring micro-amps with INA series

I'm designing BLE devices and other low power embedded systems that can consume very low energy in the range of a few micro-amps. I can't afford any expensive precision multimeters. Hence, I'm trying ...
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3answers
1k views

A really basic question about ammeters and their ranges

I was performing a basic verification of Ohm's law in a DC circuit experiment the other day, during my exams and I mistakenly used an ammeter with range 0-10A instead of the 0-1A ammeter that the ...
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36 views

How to find current and voltage of a certain appliance connected to an outlet?

Objective: I'm new to electricity and trying to convert my mirror integrated with LED work with a power bank. I need to find how much voltage and current is needed to make it work. How can I measure ...
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2answers
47 views

Explanation for Method of Monitoring Current from a Power Supply

I recently came across an interesting way to monitor current, but was not certain exactly how it works. Likewise, I was hoping that someone might be able to explain how the device measures current. ...
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1answer
58 views

High voltage and cheap differential amplifier

Can I use a LM324N (very common) op-amp to act as a high-side differential current sense op amp at high voltage? The Differential Amplifier The differential input voltage rating is 32v, but my load ...
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1answer
57 views

Low-side current sensing, raising the ground?

One of the main reasons why we don't use low-side current sensing for PSUs is that we want the ground to be, 'ground'. adding a shunt resistor will rise the ground slightly higher. In real world ...

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