# Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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### 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 ...
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 ...
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 ...
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 ...
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 ...
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)...
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 ...
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. ...
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 ...
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 ...
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 (...
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)...
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 ...
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....
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.
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 ...
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 ...
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?
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: ...
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 ...
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 ...
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....
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 ...
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 ...
61 views

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, ...
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 ...
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 ...
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 ...
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,...
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 ...
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 ...
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 ...
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 ...
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 ...
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) ...
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 ...
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 ...
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. ...
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 ...
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 ...
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 -...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...