Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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48
votes
7answers
58k views

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 ...
2
votes
2answers
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 ...
10
votes
5answers
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,...
28
votes
7answers
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 ...
0
votes
2answers
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 ...
6
votes
2answers
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 ...
56
votes
6answers
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 ...
20
votes
3answers
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 ?
10
votes
4answers
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 ...
5
votes
2answers
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 ...
16
votes
1answer
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. ...
4
votes
2answers
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, ...
7
votes
1answer
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 ?
3
votes
1answer
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?
1
vote
1answer
7k views

Measuring uA current with DMM?

I'm wondering if anyone knows the accuracy of measuring uA current with a cheep (~25$) DMM? I need to measure some low power circuits (10-500uA) and I'm deciding whether I should get an analog uA ...
6
votes
2answers
183 views

Current measurement maximum time

On my multimeter I have two current measurement connection. One for the mA and one for the A. On the ampere one there's a time limitation but not on the mA one. Also they mention in the manual a kind ...
3
votes
1answer
257 views

How to measure supply currents ranging from 1μA to 10mA?

I’m building a battery powered data logger with a microcontroller and several sensors. I’d like to measure the supply current of individual parts with idle currents in the μA range and peak currents ...
2
votes
3answers
390 views

Measuring Current in Combination Circuit with a Shunt

I've done a fair bit of looking/asking around for help with this but I'm struggling to come up with an answer .... I'd like to measure and record current in a circuit. There is a 12 VDC / 2 A power ...
1
vote
4answers
1k views

Question on the relation between Transformer's primary and secondary coil current

Suppose I have a 12-0-12 1Amp step down transformer. The primary coil is connected to 220V AC. How is the current flow in primary coil impacted in following 3 scenarios: When no load connected to ...
26
votes
2answers
13k views

What are the advantages of a shunt resistor vs. a hall effect sensor?

I'm constructing a boost converter, and I need to measure both the input current and the output current. Currents range anywhere from 25A to 200A, depending on the model. My controller is referenced ...
12
votes
6answers
18k views

How to plot current in ngspice?

I wish to plot out the current and power in ngspice. In the case of voltage, for example, if I wanted to plot the voltage at node 1 I would use: plot v(1) ...
22
votes
5answers
25k views

What is the difference between burden resistor and a normal one?

I just came across the word 'Burden Resistor'. Is it any different from a normal resistor? If it is different, where can I possibly get one? Sparkfun hasn't got one listed. Any help is appreciated....
11
votes
4answers
5k views

Is current flowing backwards a bad thing?

In the circuit below: I find it awkward that the direction of the current on the 2V power supply is running opposite to the direction of the current on the 5V power supply. In the 5V power supply the ...
10
votes
2answers
790 views

Do batteries last longer with constant current draw or spiky current draw?

Do batteries last longer with constant current draw or spiky current draw? Or, as is implied by the accepted answer to "Making a battery last a long time in a microcontroller circuit", do some ...
9
votes
1answer
3k views

Why can't a multimeter measure its own current and voltage?

Well I finally obtained another multimeter, so now I have a Mastech MS8226T and a Ben Electronic M92A. I decided to measure at which voltages would the low battery warning appear and how much current ...
7
votes
2answers
650 views

Best way to calibrate ADC for current sense MOSFET

I'm using the infinion BTS6143 as a current switch and current measurement device in combination with an STM32 controller. The BTS6143 is an integrated MOSFET with internal charge pump and \$I_{sense}...
6
votes
3answers
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). ...
4
votes
1answer
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 ...
8
votes
1answer
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 ...
2
votes
2answers
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 ...
2
votes
4answers
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 ...
2
votes
3answers
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 ...
11
votes
2answers
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?
8
votes
2answers
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) ...
7
votes
2answers
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 ...
7
votes
2answers
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 ...
6
votes
2answers
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 ...
5
votes
3answers
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 ...
4
votes
3answers
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 ...
4
votes
3answers
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 ...
3
votes
5answers
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 ...
3
votes
1answer
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 ...
3
votes
2answers
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 ...
3
votes
1answer
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 ...
3
votes
1answer
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 ...
3
votes
2answers
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 ...
2
votes
3answers
914 views

Possibly Incorrect Current Reading

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 ...
1
vote
2answers
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-...
1
vote
2answers
103 views

High side current indicator/

simulate this circuit – Schematic created using CircuitLab Hi! I am in need to make a high-side current monitor for detecting whether load (R1) is present or not. As currents running through my ...
6
votes
4answers
2k views

High-bandwidth current measurement

We need to measure +-50Amps of current (PWM) on a PCB. We need the measurement to be isolated, so I thought of using an ACS758, and feeding its output to an ADC. However, this hall effect sensor is "...