# Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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### 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 ...
2k views

### What's the most economical way to digitally measure 240V mains voltage, current and power factor?

I'm looking to capture and analyse measurements of the mains energy that I use per circuit. I've found a few consumer products that offer powerpoint energy monitoring such as the Kill-A-Watt, but PC ...
6k 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,...
24k 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 ...
469 views

### Ordinary Differential Relay Problem

The answer given in my workbook to the above problem is A. The things I was able to point out secondary c-phase current = 300A and other secondary phase currents = 0A since the entire current ...
4k views

### Measure current in high voltage (10kV)

In a plasma application (Helium or Argon Plasma), we would like to measure the current. The voltage is around 10kV AC and modulated with a function generator. Currently we only have one of those ...
17k views

### 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 ...
93k 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 ?
27k 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 ...
21k 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 ...
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. ...
3k views

### How do I design a current transformer?

I want to make a Current transformer using toroidal ferrites to measure 220/50-60Hz AC current(40A max). Is it possible? And how can I calculate secondary turns count? Ferrite properties: H = 2000, ...
2k views

### Why shunt resistance has 3 line?

I know that the there is two lines to connect it to the integrator like the below picture , so what the 3rd line do ?? how to use it ?? is it necessary ?
2k views

### What's the difference between a shunt resistor and a four-terminal resistor?

I want to know if the four-terminal resistor and the shunt resistor are the same. Is there another use for the four-terminal resistor except measuring current?
7k views

829 views

### Current sense amplifier + op-amp buffer + ADC: Measuring down to 0 with a single supply

I'm thinking about current sensing with a high dynamic range (10 mA - 20 A) and using LTC6102 as a high-side current sense amp (the voltage would be 54.6 V max, a 13S6P Li-ion battery). ...
1k views

### Current sensing at μA accuracy and ADC nonlinearity

Project context A battery-operated positioning device sends location information through GSM at regular intervals. Between the fixes, the device is in low-power mode. The battery is supposed to last ...
3k 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 ...
482 views

### Switching a current source through a MUX

I have a current source of square pulses (0-20 uA) generated by a NI 9265 device. I am trying to build a fast switching circuit using TI CD4051 multiplexer to switch the current signal between ...
2k views

### Measuring low current at very high speed

I have a circuit with a very-low-power Jennic JN5148 module with microcontroller and 2.4 GHz radio, and some low-power sensors. I have to measure the supply current of all these components, in an ...
5k views

### How much current is a powered-down ATtiny84 supposed to take?

I know this sounds like a stupid question, but I'm wondering if the datasheet has an error or something. I have an ATtiny84 connected to my bench power supply set for 3 volts. It's fused for the ...
6k 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?
10k 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) ...
269 views

### AA cells depletion

Currently I have two AA cells in series powering a 3.0v bus line for my application.Recently I am finding that one of these AA cells gets completely dead before the other. What could be the possible ...
15k views

### Calculating a burden resistor for a current transformer

Background: I follow a reference design for a single phase power meter (230 V, max 3 A). The below circuit is to measure current via a current transformer. A current transformer will be ...
968 views

### Recommended Layout for Parallel Current Sensing Resistors

I'm working with 12V DC systems and high currents (up to ~40A). In order to meet the wattage and price requirements for my design, I'm using two parallel sense resistors. The IC I'm using for sensing ...
1k views

### Total current consumed from a battery

I would like to know how could I know the current consumed from a battery using this sensor, or other similar, using a microcontroller. What I would like to know is shown in this video, where you can ...
15k views

### How to build very low cost current transformer?

Im building low cost home energy monitoring system. I want to see how much energy is used by water heater, big water pump, kitchen equipment, lightning, computer. I would be awesome if I could measure ...
6k views

### Current multiplier/divider for current measurement?

You can change a current mirror into a multiplier/divider by adding transistors on either side. Then the number of transistors defines the current ratio. The transistors have to be integrated on the ...
4k views

### Sensing BLDC motor torque using a current sensor

As it is commonly known, the torque supplied by a motor is directly proportional to the current it draws. So when a motor is under heavy load, the torque required will be more hence it would draw more ...
485 views

### Current transformer minimum frequency

I need a current transformer for an induction heating project. After searching Digi-Key for a transformer meeting my specifications (turns ratio, current, mounting type, etc.), the cheapest model I ...
2k views

### Limiting DC motor's stall current draw from power source

I've got a power supply that'll deliver 0.5-1A (depending on a later design decision), and a motor that will normally draw about 150mA, but its stall current is a whopping 2.1A. In my application I ...
652 views

### AC Power measureless using MCU, calculations problems

I'm done from the hardware design sensing the current & the voltage levels using my MCU (AVR) & some circuitry Beside I wrote the firmware to handle the ADC data & so on But I'm, having ...
347 views

### Parasitic Capacitor current of an inductor

I am doing a double pulse test on SiC MOSFETs from 100-800 V and current from 20-80 A. The schematic is shown in figure (the values are not correct though). In my first round of tests (Figure 2), I ...
7k views

### Best way to test a USB wall charger for output current

USB chargers are tricky. Or at least they are when you don't follow the standards. I have a device that uses 5V to charge a battery. The device has a USB socket, with the idea of connecting it to any ...
914 views

I'm not entirely sure if I have done the following equation correct or not, but based on the calculations, my multimeter result seems to be incorrect. I have a very simple circuit, containing a 9V ...
994 views

### Circuit Design for Current Measurement at High Voltage

We're working on a power supply unit for ionic pumps. My supply voltage is 2kV to 3kV with current varying from 0.5mA to 1mA. We wanted to add a high side current measurement indication in these units-...