Tagged Questions

Measurements of the current flowing through a circuit

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0answers
4 views

CCVS (current controlled voltage source) in practice

In my current project I'll possibly need to deploy a CCVS (Current controlled voltage source). It is transconductance amplifier or converter and many manufacturers offers transconductance amplifier ...
1
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2answers
32 views

Why are null measuring methods considered to be very precise?

I heard a professor saying "it's a null method, so it is very precise". He was talking about the force balance pressure measuring method. I think in this cathegory of methods one can include the ...
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0answers
117 views

How to sense current with transistor based design?

I am planning to build a differential amplifier for current sense purpose of microcontroller's ADC. Single ended CM amplifier should provide 3.3 V output to the ADC pin. 3.3 V, 5.2 V, and 3.7 V are ...
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1answer
18 views

Current Sensing with ACS712 on Beaglebone Black

I am planning to use my BBB to perform some current sensing and was wanting to use the ACS712 chip. The chip operates off of 5V, but the analog inputs of the BBB have a max of 1.8V. How can I wire ...
0
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1answer
26 views

Understanding High Side Current Sense OpAmp Datasheet

I'm considering the INA199A3, AD8293G80 or TS1102-100 (decreasing cost order) for a high-side current sensing application. According to my understanding the output voltage error is mainly affected by ...
0
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1answer
19 views

Si8519 AC Current Sensor usage

I'm trying to find a good and practical current sensor and I found this: Si8519 http://www.silabs.com/Support%20Documents/TechnicalDocs/Si85xx.pdf My idea is monitor AC Mains current, so this Si8519 ...
1
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2answers
75 views

Measuring Electron Beam Currents

When it comes to measuring electron beam currents with a Faraday Cup (or any that will pick up electrons and act as an anode), primarily AC and transient signals, my understanding is that one can (1) ...
1
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0answers
89 views

Reduce analog reading noise on arduino

With refer to this question: I got CTs connected to all analog pins on a Arduino Mega, connections for each pins are as mentioned here. Readings were good indoors, +- 0.1A. However, when located ...
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3answers
79 views

How is a transconductance amplifier used to measure current?

In this post Design for a Precision LCR Meter the author says: Current is measured via a transconductance amplifier (again with programmable gain) which produces a voltage proportional to the ...
1
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1answer
52 views

Current sensor with instrumentation amplifier (LT1167)

Objective I'm trying to make a current sensor that can accurately measure current up to 5A. In order to do this I'm using an instrumentation amplifier (LT1167) to measure the voltage difference ...
3
votes
2answers
80 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, ...
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2answers
93 views

How much current does a typical multimeter draw to measure resistance?

Assuming it's running on a 9V battery like most multimeters are, and the setting is on MegaOhms. How much current will be drawn from the internal battery?
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2answers
75 views

Series RLC measurement result different with theory

I am measuring the current and voltage in simple RLC circuit: However,the result that I measured show big difference with the simulation result using Multisim. Why is there are a big difference ...
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1answer
49 views

Calculate Current [closed]

how to i calculate current( Before Resistance ) from these parameters Voltage before Resistance Voltage after resistance Resistor Value Current After Resistance
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1answer
324 views

What causes inaccuracy over time on a DMM?

Here is a piece of information from a datasheet of a DMM. The accuracy rates seemed interesting for me. I wonder what causes difference in the accuracy, especially the changes after 24 hrs? Is it only ...
0
votes
1answer
122 views

How much power does a wireless mouse use? [closed]

I have seen many answers online to how much power the USB dongle linked to a wireless mouse uses, but nothing about how much power the actual mouse draws from its batteries. What is a ball-park ...
0
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0answers
59 views

Voltage/current Monitoring - MAX4172 + ADC vs. INA219

I'd like to add some monitoring of voltage and current on the +5V and +3.3V supply rails of a development board power supply. I'm currently debating between two approaches. The first approach is to ...
2
votes
4answers
276 views

Current sensor measuring circuit

I am planning to design Rshunt basis current measuring. My current measuring range is 1A~2A. I need analog output of 0~5V analog with 1% accuracy. How can I do this? I found conversion circuit here. ...
0
votes
1answer
90 views

milliwatt-hour meter [closed]

I am looking for a way to design something that can tell me the cumulative power draw of a circuit -- the same concept as a Kill-a-Watt, but measuring mWh rather than KWh. An added bonus would be the ...
0
votes
1answer
51 views

How do I place a long wire to make the EMI and inductance minimum?

I'm going to measure high current. After seeing that there is not a lot of low valued sensor resistors in the market and the available ones are very expensive, I decided to make my own current sensing ...
0
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5answers
153 views

ADC implementation

I want to sense the voltage across the resistor R1 (i.e convert it into digital form). I only have comparators available with me and no other hardware (ADC is not available). Is there any way I ...
0
votes
1answer
67 views

measuring current to 100uA accuracy in a battery powered circuit

I'm trying to figure out the best way to measure and log current consumption in my circuit, which houses an ATMega2560 and a number of sensors and servos. Using a DMM, I see about 100mA draw when ...
0
votes
1answer
92 views

Known voltage/current source

I am working on an EVM for an electricity meter. Its manual says the EVM requires a known voltage and current source for the calibration. I bought a power supply and measure the output of the PSU by ...
2
votes
2answers
80 views

Inductors in series with different currents

I'm having trouble finding the differential equation that describes the circuit, at t=0 10A flow through L1 and 0A through L2, since current can't change instantaneously. But they're in series so ...
2
votes
3answers
288 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 ...
0
votes
1answer
54 views

Three phase motor current verification

I want to verify that the quadrature current through a permanent magnet synchronous motor (PMSM) is actually the same amount as I commanded the field-oriented control (FOC) motor controller to push it ...
1
vote
4answers
238 views

How do I average a complex waveform?

I am trying to figure out how long my project will last on a single battery. It's powered by a single AA battery with an NCP1402 3.3 volt boost converter. I've determined that the target circuit draws ...
2
votes
2answers
223 views

Solar power monitoring with Raspberry Pi

I want to measure the current and voltage from a set of small solar panels (about 10V and 100mA but not settled yet) using a Raspberry Pi. There will be between 4 and 6 panels. This project will ...
0
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0answers
82 views

How to measure the peak current (inrush current) and results assessment

I would like to peak the inrush current of a controller. The voltage input of the system is 24V and the only thing which is available, is an oscilloscope and a variety of resistors. The basic idea is ...
0
votes
4answers
124 views

Is it possible to power AVR micro project with just one coin cell battery?

My current project setup is: ATmega328P micro with 32 LEDS driven by 4 8-bit shift registers. System without LEDs draws 20mA of current continuously. With all LEDs lit at the same time, it draws ...
0
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0answers
75 views

DC shunt current measuring

I am trying to build DC shunt based high current measuring using bus bar. Each bus bar has a 1000V 20A rating. Is any IC available to measure? I have done with hall sensor based. So my plan to build ...
2
votes
2answers
516 views

calculating a burden resistor for a current transformer

Background: I follow a reference design for a single phase power meter (230V, max 3A). The below circuit is to measure current via a current transformer. a CT will be connected to...
17
votes
1answer
852 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 ...
0
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0answers
47 views

Determine current so that you have circular polarization

I have a problem in resolving the first point of exercise on antennas. Note: if it wasn't clear \$\phi_1\$ and \$\phi_2\$ are phase of alternate currents \$I_1\$ and \$I_2\$ I know that to have a ...
2
votes
3answers
635 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 ...
2
votes
2answers
93 views

Simple PWM regulator, current measurement without high-side current sensing

I have a very simple Lead-Acid battery charger with slow (1kHz) PWM regulator. I would like to add current and voltage measurement (with PIC18F ADC - 200kSPS). I have no problem with voltage ...
1
vote
2answers
155 views

Measuring Current Consumption of USB Devices

I was trying to measure the current draw of a USB-powered device (a Raspberry Pi) to determine the suitability of powering from an external battery pack. So I took a USB cable, split the +5v (red) ...
-1
votes
2answers
767 views

RMS vs DC(mean value) when calculating power of pulsed or rectified signals

When I have either a rectified signal (like the unfiltered rectified sine wave out of a diode bridge) or say a fast pulsed signal feeding a LED and resistor, in which both the DC component and the RMS ...
0
votes
0answers
310 views

How to measure current waveform in Proteus?

How are current waveforms measured in Proteus? There is a current probe in Proteus but I think it is giving me absurd results. I want to plot the current flowing through a resistor. There is a graph ...
0
votes
2answers
109 views

Small-value current sense resistor value changes after assembly

I'm using a small value (~60milliohm) and small-package (0402) resistor to measure current. When I probe the resistance with a (nice Agilent) DMM, the resistance is more like 100millohm though and ...
1
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0answers
24 views

Current consumption estimate for frequency dependent specification

I am carefully calculating current consumption for current budget limited device. Certain switching devices such as integrated opto-isolator gives current consumption specification in a form of X ...
0
votes
1answer
75 views

Shunt capacitance in applications not involving photo diodes

I have read a lot of articles about how to determine the correct feedback compensation capacitors capacitance in transimpedance amplifier circuits, but they "all" use the photodiode as an example. ...
2
votes
3answers
140 views

Measuring DC Currents

I developed a board and I like to measure the power for each block. Power can be a few micro amps to a few hundred mAs. (Depending on the block). I have zero ohm resistors at the input of each block ...
1
vote
2answers
331 views

What is the significance of 75mV in available 100A current shunt resistors?

I'm considering doing part of How to Install an Ammeter in the Black & Decker CMM1200 Cordless Electric Mower but first with just a shunt resistor and voltmeter, versus hooking in a dial ammeter ...
0
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3answers
97 views

AC current transducer symbol

What does the symbol in the red circle mean? (Product page)
2
votes
3answers
197 views

What is the unit V/V?

I came across this when I was browsing through the data sheets for a current sense amplifier such as the LT6100. It reads: "Fixed gains of 10, 12.5, 20, 25, 40, 50V/V are obtained by simply strapping ...
0
votes
1answer
169 views

Lightning Connector Power Output rating/ Apple Policy

I am currently in the process of developing an external antenna for smartphones, so the answer of the following question(s) pertains to the feasibility of this product. What is the line level output ...
0
votes
0answers
76 views

Analog output using a current-output DAC and resistors

Does it make sense to have a 4-20mA output DAC and use a precision (~1%) load resistor to convert this to a voltage output with the goal of having a selectable current/voltage analog output? For ...
0
votes
2answers
250 views

What's the best MOSFET for switching small currents?

What are the most important characteristics to look for in a MOSFET for switch a precision 50nA load? The MOSFET should be able to switch the load on or off within 1us. The overshoot/undershoot ...
0
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2answers
135 views

Transistor for 4-20 mA voltage drop resistor connection?

This is for converting a 4-20 mA current loop signal to a voltage. Is it okay to connect the resistor for measuring voltage drop with a transistor to allow for switching between voltage and current ...