Measurements of the current flowing through a circuit

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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 ...
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3answers
175 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
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2answers
62 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 ...
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2answers
80 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) ...
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2answers
113 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 ...
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49 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 ...
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2answers
97 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 ...
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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 ...
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1answer
51 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. ...
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3answers
97 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 ...
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2answers
122 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 ...
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3answers
63 views

AC current transducer symbol

What does the symbol in the red circle mean? (Product page)
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1answer
78 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 ...
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1answer
72 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 ...
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0answers
47 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 ...
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2answers
200 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 ...
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2answers
102 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 ...
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3answers
178 views

Working out mAh from current and time

If I know how many millamps I'm drawing, and also for how many milliseconds, how do I calculate this to mAh consumed?
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2answers
94 views

What will be the value of Vo

simulate this circuit – Schematic created using CircuitLab This ckt comes as a question in our previous year exam. what will be current " I " and voltage drop " Vo " . It'll be very ...
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1answer
129 views

How to measure car battery current precisely in wide range (starter current, charging)

I want to measure car battery currents in high resolution and in wide range and both directions (including engine start and charging currents). I don't need very high precision measurement, but I ...
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2answers
116 views

Stepper current measurement puzzle

The basic puzzle: how to conveniently view stepper motor current on a scope? Edit 2014-04-14: More-sophisticated schematic and description. I am building a test fixture to examine the behavior and ...
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1answer
84 views

Measuring smartphone's battery State-of-Charge during charging

I'm designing a mobile device that uses a Li-Ion battery. It is required to indicate to the user the State-of-Charge of the battery, similar to how it's done in smartphones. At first I considered ...
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1answer
114 views

Circuit to provide 0-5 V output proportional to 0-30 A from C.T?

I want to design a circuit to protect oveload current of 30A.I have a controller board(PLC) which accepts the voltage range of 0-5 as an input and C.T with 1:7000 turns which can maesure 0.5 -60 ...
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1answer
65 views

High-current monitoring circuit

I have the following circuitry: Battery Supply => Current Monitoring Circuitry => DC Motors Battery Supply: 4AA NiMH batteries - 4*1.2V (1.5mAh * 4) Current Monitoring Circuitry: Max 4378 chip ...
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1answer
124 views

Max output current per I/O pins from Basys2 (SPARTAN 3E) board [closed]

I am trying to drive IR leds out of spartan 3E fpga on xilinx's BASYS2 board. I will be using external current amplifier to drive the IR lEDs with control singal from the FPGA. I need to know the max ...
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3answers
84 views

Voltage dip on MOSFET switchable current shunt

I have the following circuit built up in LTSpice which will be used to switch in different sense resistors for current measurements. The mAEn signal switches the M1 transistor on at t=10ms which ...
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1answer
130 views

Current Transformer giving a reading when not clamped around a wire

A split core current transformers is currently clamped around a live wire. One end of the transformer's output wires are connected to the analog pin of an Arduino and the other end has a 2.5V bias ...
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2answers
45 views

Galvanic Voltage and Current strength

This is a mouthful! I have a copper pipe fixed with zink coated (galvanised) saddles. I want to ascertain what the voltage would be in the dissimilar metal galvanic reaction between zinc and copper? ...
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1answer
69 views

What determines the frequency range of a current transformer?

Per the title, what physical or construction parameters determine the frequency range of a current transformer? I happen to be looking at these two from mouser, but I'm sure the question is generic ...
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2answers
245 views

How to sense current being used by motors

I have an Arduino project that provides 12v power to run motors, etc... I want to be able to measure the current (amps) that the motors are using (0 to 500ma). 12v comes from a battery, but that ...
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2answers
350 views

Measuring average current with uC and current shunt

This is my first post. I'm a software guy trying to do hardware so be gentle :) Circuit I'm designing a small circuit (see pic, and sorry for messy schematic) that plain and simply is a bunch of ...
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3answers
180 views

Using built-in gain on ADC vs different current-transformer?

I'm looking to eventually build an energy monitoring circuit using a raspberryPi as the controller and some type of ADC as the collector. I'm generally following the architecture of the emonTx used ...
4
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1answer
197 views

How to measure the PWM current with a DMM

I have a Fluke 87V, which is a True-RMS DMM, and I would like to measure the current in my circuit. I have 2 motors being driven by a PWM so I wonder if the DC current or the AC current measurement of ...
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1answer
155 views

burden resistor and/or voltage divider in an energy-sensing CT setup

I want to (eventually) build myself a home power monitor using basic current transformers. While reading on various circuit designs, I've stumbled upon what must be a very basic question. If we look ...
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310 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?
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130 views

Isolation in Resistive Current Sensor

In resistive current sensor, can it have two different supplies for the voltage divider circuit and the differential op-amp circuit? Since the op-amp only gets the voltage difference.
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4answers
123 views

Check if electrical current exists in high voltage

I'm thinking about a simple home automation project, containing a Rasberry Pi, a Sainsmart SPDT Relay, I would like to switch the state of a ordinary bulb (ON , OFF) using both the relay and the old ...
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3answers
356 views

Home Current Meter - is this a good solution?

I want to build a simple current meter to measure my power usage at home, and have the data sent to my blog's database. (I know there are similar solutions out there, but this project seems engaging ...
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2answers
54 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 ...
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1answer
205 views

Measuring the Current Draw from a LIPO Battery

I have been working with LIPO batteries to power my portable projects for a while (mostly in RC aircraft), but when using them, I have always had to guess as to how much charge is remaining. Now, I am ...
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1answer
112 views

Current Transformer - example (basic) circuit request

I'm trying to setup an XBee to monitor power usage of a device. At the moment, I'm trying to get a basic circuit setup on a breadboard, without the XBee. I have purchased a ...
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0answers
55 views

Choosing the correct transimpedance amplifier for my application

Intro: I am to convert current to voltage using a transimpedance amplifier. I have some specifications and I need to know what op. amp. parameters I have to worry about and approximate values of ...
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1answer
252 views

Measuring 230V AC current with low sample rate

I have a resistive load of order of 1kOhm, on a 230V AC circuit. The load's resistance varies a little over time - the current draw may float between some 0.2 - 0.25A, slowly (order of minutes). I ...
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2answers
90 views

Input current in an ic

I know that measuring amperage in a circuit, makes sense when you have load, but what if you have an ic component? I want to power supply operational amplifier LM741 ...
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2answers
151 views

How to measure current with multimeter

I want to measure both voltage and current from an output expansion port, of the BeagleBoard-xM. I managed to measure voltage by putting measuring lead (red) to the expansion port and reference lead ...
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2answers
115 views

Correct calculation of conductance/susceptane and from there to admittance, impedance, resistance and reactance.

I am sending a sine wave through a unknown RC circuit. At the other side I have a current-to-voltage converter (transimpedance amplifier) measuring the current indirectly as voltage. I am using IQ ...
5
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2answers
112 views

Accuracy when measuring current (mAmps) and small voltages

I'm looking at a circuit (part of a bigger circuit) that consist of a 10 ohm resistor and a red LED. It's running on 2.05V (checked with 2 different multimeters, ranging from from 2.047V to 2.05V). ...
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1answer
143 views

Battery measurement after charge

I got a Ni-Cd battery (8 AA) 9.6 V, 700mAh. After a 2 hours charge by an AC/DC adaptor (9.6 V, 250 mA) I take the following measurements by the multimeter: Voltage: 11.28 V (DC) Current: almost 10 A ...
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1answer
157 views

Clarify multimeter current reading range?

I'm a bit confused about the range on my multimeter. I have connected the multimeter to a 5V USB wall charger rated at 1.3A. When I'm measuring voltage, everything makes sense. It shows a 1 for 200m ...
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2answers
256 views

Checking for a short in a circuit with a large capacitor?

I'm developing a small testing application for my company that tests various hardware and software functionality. I do however have a problem developing a simple way to check for short circuits in ...