Questions tagged [current-sensing]

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19
votes
4answers
4k views

Current sensing nA to mA

I need to sense the current of a target MCU through various periods of its on/sleep/off state and then need to send this data back to another interface MCU to read out the value. They will be both on ...
7
votes
1answer
561 views

Can a floating capacitor terminal be used to collect electrons?

I want to collect charge from an electron beam source. For that, I'm proposing to put a floating capacitor with its bottom terminal floating and directly exposed to the electron beam gun. The top ...
6
votes
8answers
14k views

What is negative current?

I understand that voltage is relative to ground, so that can be negative. However, I'm currently looking at current-sensors (ACS712 current sensor) and in the performance characteristics table, it ...
5
votes
2answers
761 views

The benefit to make or use a surface mount 4-terminal current sensing resistor

I find some precision SMD resistors are 4-terminal, like vishay's CSM3637P. It's constructed as below: It seems it only make a slot on each pad, then get two extra pad to do the voltage measurement. ...
5
votes
2answers
2k views

Measuring average current consumption in hardware

I'm working on a very low power budget, battery powered project. This project is allowed to draw 15uA (average) at 3v. The microcontroller we're using draws 4-10mA when active, and 2-3uA when asleep....
5
votes
1answer
278 views

Wide range current sensing at +5kVDC

I am working on a control and interface board for high voltage supplies, which requires some current measurement to be implemented. The general terms of the question are similar to this one. The ...
5
votes
1answer
901 views

Noise problems in current sensing

I have the following circuit: simulate this circuit – Schematic created using CircuitLab I am using a motor from an electric bike, as a generator and I am rotating it using a drill, to test ...
4
votes
3answers
2k views

Op amp with transistor in feedback

I am currently looking for a high side current sense IC. I have noticed that most of them that are without galvanic separation, are using an op amp with bjt transistor like in bellow schematics: The ...
4
votes
4answers
106 views

Charge indicator with comparator - very sensitive to noise

I need an indicator when the current from my charger is larger than 100mA. I tried the below circuit but this seems very sensitivity to noise. Probably I am getting some ripple in the mV range from ...
3
votes
2answers
3k views

Transimpedance vs. Non-Inverting Amp for high sensitivity application

In simple analysis, these two circuits give the same result ... i.e. producing 1V output for a 10pA input. Is there any advantage of one over the other in practice? I am measuring currents in the ...
3
votes
2answers
220 views

High side current sensing for negative high voltage

I need to monitor the current for a negative high voltage supply. I implemented the following circuit in a simulation program: https://www.maximintegrated.com/en/app-notes/index.mvp/id/1867 But ...
2
votes
3answers
629 views

Detecting switch closure

Any techniques/circuits/sensors that can determine the open/closed state of a set of contacts, independently of whatever power or signals are being switched by the contacts? Obviously easy if there's ...
2
votes
1answer
921 views

Shunt resistors and PCB layout

I have several questions about the current sensing through a resistance. The resistances are 2-SMD package and I will use the 4-wire kelvin method for the layout.(see image) Specifically, there are ...
2
votes
1answer
6k views

ESP32 using acs712 give wrong values

I'm trying to measure current with acs712 30A current sensor connecting to NodeMCU-32S but I'm getting wrong and unstable values. For zero current the ADC pin should read value of 2048 (esp has 12 bit ...
2
votes
1answer
92 views

Low Side Current Sensing Grounding Question

I recently made a low side current sense circuit to test a power supply. It works well, but I am trying to understand the strange behavior that happens when I apply the negative lead of my probe to ...
2
votes
1answer
81 views

Measuring AC Current at High Voltages (up to 600VAC)

I've been looking at various ways to measure current for a while now, and am stumped on how to read high-side AC Current Measurements ohmically (no Hall Effect sensors). My initial thought was to use ...
2
votes
2answers
101 views

Current Sensing Amplifier Circuit explained

I've been trying to understand why each every comment is in the circuit shown. I understand that the amp is taking the voltage drop across the Rsense and amplifying it such that the current across it ...
2
votes
3answers
1k views

High-side current sensing diagram

I have a load that can be connected or disconnected from a +5V source (let's assume there is a switch). My target is to trigger an output to high-level voltage if the load is connected, and trigger it ...
2
votes
1answer
739 views

Automatic ranging current sensing

I am trying to implement a current shunt sensing circuit. This should be automatic and currently i want it to measure uA to around 200mA, and Change to the mA range at around 200uA. This is to profile ...
2
votes
0answers
175 views

High voltage 1100 V current sense on the high side

I have the circuit that you see below. My load is a photomultiplier tube equivalent to a 3.63Mohm resistor. My power supply can deliver max 4W (2kV and 2mA). I use it on 1100V and the load draws ~...
2
votes
0answers
127 views

Problem simulating LMP8645 current sense amplfiier in LTspice

Basically the problem i am getting is that the output offset voltage is extremely large (58mv) here is the datasheet for the amp: http://www.ti.com/lit/ds/symlink/lmp8645hv.pdf on page 9 it shows ...
1
vote
2answers
655 views

High-side current sensing with a rail-bound instrumentation amplifier?

I know that current shunt monitor ICs and high common-mode voltage differential amplifiers like the INA117 and AD629 exist but I'd like to know if it's possible to use a regular instrumentation ...
1
vote
2answers
4k views

AC Current Sensing Switch Using Current Transformer

I'm struggling to design a circuit that will interpret signals from a SCT013 current transformer and trigger a constant 5v signal (which will go to a microcontroller) when a certain current threshold ...
1
vote
1answer
285 views

What are shunts, as related to their use in current sensing in microcontrollers?

Within the manual for the I/O module I'm using (a Loytec LIOB-153) there are wiring diagrams to aid in wiring up your sensors and other inputs/outputs. There are two wiring diagrams for the purpose of ...
1
vote
2answers
400 views

Four-terminal resistor pinout?

Anyone can tell me (or preferably, point me to a source that explicitly shows) the pinout of the 4-pin current-sense resistors? I'm seeing the datasheets for three different models (including Rideon'...
1
vote
3answers
473 views

AC current sensing using micro-controller and suitable circuit

I'm working on the project in which I need to measure AC current. The main problem I am facing is small current amplitude. I have to obtain the current waveform(I need complete waveform not just RMS ...
1
vote
1answer
41 views

XADC Current Sensing Reference Design

Please refer to this reference design for AC701 (snippet below). The schematics, specifically the current sensing sections in pages 34-36, show this: I want to understand why, for the REF output of ...
1
vote
1answer
197 views

Precision of estimating power consumption with a current sensor

When estimating power consumption with a current sensor, what is the usual precision that can be achieved for home appliances? I'd like to make a simple circuit using such a sensor and a ...
1
vote
2answers
791 views

Current sensing with Rdson?

I'm fooling around with a PMOS, a Fairchild FDD6637, and pondering whether it would be possible to use Rdson as a sort of shunt-resistance for measuring the voltage drop, to get the amount of current ...
1
vote
1answer
30 views

Dedicated current sense amplifier vs simp,e difference amplifier

I need to implement low-side current sensing for a H-bridge motor driver. While there are dedicated current sense amplifiers such as TI’s INA180, can I use a simple difference amplifier for this with ...
1
vote
1answer
363 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 ...
1
vote
1answer
528 views

High side, high voltage, micro ampere current sensing

I am working on a project in which I am required to sense current in micro ampere range from a 2kV power supply. Here is a link of an article which I am referring. https://www.maximintegrated.com/en/...
1
vote
2answers
56 views

Why most non-invasive current sensors have a minijack at the other end?

If I search on google for non-invasive current sensor and click on the images tab, in most cases, I see a minijack at the other side of the wire. What is the reason for this? Is this minijack supposed ...
1
vote
1answer
182 views

Current sense op-amp with integrated shunt vs expensive resistor

To simplify my question lets assume: I need to convert +/-7.07A RMS AC current into +/-707mV RMS voltage with high acurracy (0.1% or better). It may be also higher voltage, up to +/-2.5Vpk. For now ...
1
vote
1answer
62 views

Load sensing relay/power switch/adapter which switches on when it detects some load on its input

Complete newbie here. I'm not using the right terms, so my apologies in advance. The problem is simple. I want my powered computer speakers (2.1) to turn off when the computer is turned off. I have ...
1
vote
2answers
136 views

Over-current sense

I am using a circuit shown below. it is designed to sense 1.5 A whenever the load takes current >= 1.5 A. Rsen senses the related voltage and activates the transistor. Here I use a Rsen = 0.46 R(0.7V/...
1
vote
2answers
327 views

Placement of sense resistor on DC-DC converter

For my design I am using DC-DC converters LTM4620 and LTM4644, which integrate the MOSFETs and the inductor in the chip. For measuring the output current, I will add a sense resistor in each output ...
1
vote
2answers
340 views

Design of low current sensor from 50mA to 2A in a dc-dc buck converter

I would like to sense the current from a path where a current of 50mA to 2 A is flowing to the load. Can I use simple differential amp with gain across the Rsense =20mohm or is there any contemporary ...
1
vote
1answer
1k views

Unipolar Hall current sensor signal conditioning for 5v ADC

Need help. I need to convert signal (0v to 5v) from Hall-based unipolar current sensor measuring the power line from the 84v 4kW battery pack to 5v MCU based ADC converter. Although both – the sensor ...
1
vote
0answers
43 views

Detect Battery Insertion in USB Charging Circuit

I'm using an MCP73831T as the charger IC, I've figured out how to detect the charging/charged, this was easy, however, I would like to know when the battery is actually plugged in, I know when the usb ...
1
vote
1answer
144 views

Reading registers from ACS71020 over SPI

I'm trying to read registers from current-sensing chip ACS71020 connected over SPI. This is how I initialize the SPI: ...
1
vote
2answers
70 views

AC phase current sensing using Isolated delta-sigma modulator

I am trying to design a isolated AC current sensor. I've chosen the AMC1106 Isolated Delta-Sigma Modulator. (change my mind if you think there is a better solution for 220V AC; 2A Max; 0.25%) The ...
1
vote
1answer
249 views

Current Sensing with Op-Amp, do I need a shunt resistor in series with the load on the output?

Hi I am building a circuit to measure current draw from a load, I opted for a voltage follower with a transistor and a shunt in between, The transistor is needed to allow higher currents to flow ...
1
vote
0answers
47 views

Buck converter design using MCP1630V

I have already designed a buck converter with the following specifications using an MCP19035: Vin=14V, Vout=1.8V, Fc=63kHz(Crossover frequency), Vref=0.6V, Iout=10A step load High IOH=7.5A step ...
1
vote
0answers
51 views

Using a switching DC-DC converter in high dynamic range current/voltage sensing

I'm thinking of making a power meter circuit which will have a high-side current-sensing amp (LTC6102), a resistive voltage divider for sensing the voltage, a dual op-amp (OPA2365) as a buffer for the ...
1
vote
2answers
338 views

Differential amplifier for current measurement

I'm studying reference design from TI (pdf).This design shows the solenoid control circuit. I was interested, why a differential amplifier is used to measure the current? Why not use non-inverting ...
1
vote
1answer
84 views

Current sensing application

The purpose of the application is to maintain a constant current at the load, even if the resistance changes. I understand that the ADC is reporting the voltage and current values at the load to the ...
1
vote
3answers
1k views

Spikes - DC Motor Current Sensing

I'm using a drv8838 to run a small dc motor (<1A). For current sensing I set up a INA199 (see layout). I'm also using a RC lowpass with a cut off frequency of around 70Hz to filter the shunt ...
1
vote
1answer
131 views

Common mode error formula from TI seems counter intuitive

I'm working on an application to measure current in a buck converter using a current sense amplifier. According to this video from Texas instriment, the equation for common mode error is same as eqn 1 ...
1
vote
1answer
167 views

Current sense amplifier working principle

i am running a bldc motor Infineon TLE9879 chip. Now i want to measure the current flowing through the motor. so i use the current sense amplifier where the motor current is converted to a voltage by ...