Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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19
votes
8answers
6k 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 ...
0
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0answers
31 views

Diff Op-Amp in current measurement ignores input [duplicate]

I'm working on a small project which involves current measurement. I'm using R10 to measure Voltage drop (100 mV) when 10 mA current goes through it. Next I'm amplifing that signal around 37 times ...
0
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1answer
53 views

How to select shunt resistor value of the below circuit? We can use Ohm's law but I am still a bit confused

I am very new to hardware development. I am learning all the basics to design a battery management system for electric vehicles in the future. I would like to know how to select a shunt resistor for ...
-2
votes
2answers
58 views

Constant current density

I am reading an article that says ... constant current density of \$−1.0\,\mathrm{A \cdot cm^{-2}}\$ Let's say that I have material that's \$2\,\mathrm{cm^{2}}\$, how would I calculate what's the ...
0
votes
0answers
38 views

Is it needed a relay snubber in an ammeter?

I'm designing a picoammeter for an academic project, with different current ranges. To switch between current ranges I should use some relay, driven by a micro. This kind of ammeter should be able to ...
0
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2answers
81 views

MOSFET with very low Rds_on for very small current

I'm building a uCurrent Gold clone (https://www.digikey.ch/reference-designs/de/sensor-solutions/current-sensing/2637) - with a digital interface (measuring the voltage directly with a microcontroller)...
0
votes
1answer
48 views

Measuring current using ACS712 interfaced with ESP8266

I'm using ESP8266 interfaced with ACS712 current sensor to measure current and voltage. However it displays some values without any load being applied, and after applying the load, the changes are ...
2
votes
0answers
30 views

Trouble understanding how dependent current sources affect a circuit (Two-port networks)

While reviewing a problem from my recent test on two-port networks I noticed that it made its way online. When someone was explaining the solution they utilized a point that I just completely missed. ...
1
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1answer
77 views

Can the two same current monitoring ICs give different results?

Have trouble testing of 30 pieces INA250A4PWR circuits like below. Produced as PCBA. According to test results 21 out of 30 have mainly 1.98 V/A gain ratio. But, 9 out of 30 have mainly 1.55 V/A ...
0
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2answers
83 views

Measuring nano amp range current consumption

I am looking to buy one of Joulescope, ZS-2102-A (angler circuits) or Otii (QOITech) to measure power consumption and get graphs of current consumption for some low power BLE/WIFI devices. Does any ...
2
votes
2answers
88 views

how to measure current of high voltage 150Hz pwm signal?

I have a step-up converter which produces 130V DC and 12mA max current I generate 130V pulses using an optoisolator PWM duty vary between 10 to 50 (255 max) at 150Hz frequency, but my load (...
0
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0answers
38 views

ACS712 interfacing with MCP3208 and Raspberry Pi

I've managed to capture a voltage signal from a 10Vpp @ 50Hz source, level shifted to (0-3.3V). My ADC (MCP3208) is powered by 3.3Vcc. How can I measure the current flowing through it using ACS712 (5A)...
0
votes
1answer
45 views

Calculating Energy Consumption Using a Current Sensor and Voltage Sensor

I'm creating a PCBA that uses a hall-effect sensor to measure current and a transformer rectifier design to measure the mains voltage. The voltage is 110-240 V, ~60 Hz. I wrote a digital filter and ...
0
votes
1answer
84 views

How to set the resistor value for INA219

I managed to understand how to write/read data from the INA219 directly, using just linux/i2c-dev. When I was planning my PCB and Bill of materials with my supervisor he suggested I should use a 0....
0
votes
1answer
30 views

Receiving a 4 to 20mA signal with R Click board

I have this sensor that is supplied with 12V and gives out a 4 to 20mA signal. Would this 4 to 20ma receiving board be capable of reading the signal? I wasnt sure if the 12V would blow the board.
0
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0answers
43 views

Analyzing automatic current switch

I'm trying to learn more about automatic current range switch and stumbled across Nordic's nRF6707 power profiler kit that has very interesting topology to choose between three different current ...
0
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2answers
45 views

AD8221 for high side small current measurement

I'm trying to design a power supply for an academic project, which can supply +/-10V and can also measure the output current, hopefully down to nA range for a maximum of 5mA. To perform the current ...
1
vote
2answers
63 views

How do they produce batteries with the same voltage but different current?

If we take a 12V battery, according to its work place that it works in different current consume. How do they make batteries with the same voltage but different current flow, and why?
0
votes
1answer
42 views

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: ...
1
vote
1answer
58 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 ...
1
vote
3answers
124 views

How to do i solve this electrical circuit? [closed]

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 ...
0
votes
1answer
64 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....
0
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0answers
33 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 ...
1
vote
1answer
58 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 ...
2
votes
3answers
61 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, ...
0
votes
0answers
28 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 ...
0
votes
0answers
21 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 ...
1
vote
1answer
148 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 ...
0
votes
1answer
71 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,...
0
votes
1answer
87 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 ...
0
votes
0answers
53 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 ...
0
votes
2answers
82 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 ...
0
votes
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 ...
0
votes
3answers
101 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 ...
0
votes
1answer
55 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) ...
2
votes
3answers
265 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 ...
4
votes
1answer
187 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 ...
0
votes
1answer
88 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. ...
0
votes
2answers
106 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 ...
0
votes
4answers
92 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 ...
1
vote
1answer
58 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 -...
0
votes
1answer
84 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 ...
1
vote
1answer
71 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 ...
0
votes
2answers
74 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 ...
0
votes
1answer
165 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 ...
0
votes
1answer
76 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 ...
1
vote
1answer
44 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 ...
0
votes
2answers
83 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 ...
0
votes
2answers
130 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? ...
3
votes
1answer
343 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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