Measurements of the current flowing through a circuit

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4
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1answer
71 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 ...
2
votes
2answers
68 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 ...
0
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1answer
33 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 ...
0
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1answer
66 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 ...
0
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1answer
50 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 ...
-3
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1answer
50 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 ...
0
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3answers
70 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 ...
2
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1answer
83 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 ...
0
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2answers
42 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? ...
4
votes
1answer
46 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 ...
0
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2answers
120 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 ...
10
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2answers
253 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 ...
2
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3answers
112 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 ...
3
votes
1answer
77 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 ...
0
votes
1answer
67 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 ...
6
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2answers
202 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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2answers
86 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
107 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 ...
1
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3answers
280 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 ...
3
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2answers
50 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 ...
2
votes
1answer
148 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 ...
0
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1answer
87 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 ...
0
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0answers
48 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 ...
0
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1answer
152 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
75 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 ...
0
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2answers
129 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 ...
0
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2answers
92 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
104 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). ...
0
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1answer
124 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
101 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 ...
6
votes
2answers
249 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 ...
0
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2answers
159 views

Wide range current conversion transimpedance amplifier

I am struggling trying to think out a solution to design a transimpedance amplifier (TIA) which can convert 100 nA to 10 mA. This is 5 decades. I want to be able to amplify these to 1.5V minimum. (3V ...
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1answer
84 views

Digital potmeter in transimpedance amplifier feedback

I am considering using a digital potmeter with, e.g., I2C interface as the resistor in the feedback loop of my transimpedance amplifier. I am concerned about this. Will this add any additional noise ...
1
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1answer
263 views

PLC to act as or simulate 4-20 mA transducer

I have a PLC Control system that measures a few 4-20 mA pressure sensors. Today we test these with loop calibrators on each channel. I want to set up a PLC that simulates these pressure sensors so I ...
8
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2answers
276 views

Why does a multimeter put more voltage to measure a smaller resistance?

I noticed this behaviour on two different multimeters (different models and brands as well). At first I did not put a multimeter in the way to measure how much voltage changed for the different scales ...
3
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3answers
162 views

I'm looking for a low budget current sensors for AC

I'm looking for a low budget (< 10$ per sensor) sensor for measuring AC current up to 20 A. I found many current transformers but they go up to 5 or 10 A. Any idea what types would fit? ...
0
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1answer
261 views

Reading AC signal from a XBee analog input pin

I'm trying to use a ACS756SCA-100B - 100A Hall Effect-Based Linear Current Sensor IC (SCT-013-030) with a precision of 20 mV/A. My objective is to read input voltage coming from the sensor into the ...
0
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1answer
129 views

What is the minimum current a current transformer can sense?

Datasheet of AS-100 mentions a maximum current it can sense before saturation, but what is the minimum current it can sense. For instance, if I put 10 mA 50Hz through a conductor passing through the ...
3
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0answers
107 views

Calculating reflections

I just solved a problem in my homework. I had to calculate the reflection waves and I was given the following data: // Resistance R0 = 120 Ω line impedance Ri = 90 Ω resistance at input Rb = 1 ...
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2answers
94 views

Hall Effect Current Sensor IC Data Sheet

I'm feeling like an idiot here. I've found this great little IC that will do the job I want but I can't seem to figure out what the max voltage is that can be supplied for sensing. The IC runs on ...
0
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3answers
174 views

FPGA Power measurement

Are there any methods by which one could measure the current being drawn by an FPGA in real time i.e., when it is actually deployed in a working system? Where can I get some information about them?
2
votes
1answer
113 views

Split-Core Current Transformer - Disconnecting secondary load questions

I have heard that disconnecting the secondary load from a current transformer while the primary line is passing current causes a huge voltage spike (from a question about CTs that I can't find again). ...
0
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2answers
422 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 ...
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2answers
205 views

Current transformer as Sensor, can it sense rectified DC current?

I have been using an inductor around a 230V AC wire ground-side of the switch to check for current in a wire, it is part of control mechanism. I have to add a rectifier now, so occasionally the ...
3
votes
2answers
266 views

Low side Current sensor design

I need a suggestion on a good amplifier design for a current sensor. The requirement is: Operating voltage between 2.7 to 6.0V Able to output 3.3V when a 10A current is flowing through sensing ...
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3answers
395 views

Circuit to switch power when detecting current (40mA/12V)

I am looking for a way to supply power to some consumers (sensors) only while another consumer (datalogger) draws power. All consumers run from the same 12v car battery. The datalogger wakes up ...
0
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1answer
54 views

Low TC resistors for current measurement

I have a back-burner project to take an old bench power supply and retro-fit it with two 4 digit LED displays for current and voltage. The power supply is 3A/30V, so four digits means 3000 count and ...
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1answer
114 views

Can current still be (alternatively) measured with a blown multimeter fuse?

With a blown fuse in a multimeter, is it still possible to measure current of a device by somehow measuring voltage and resistance? If so, how would this work? Do specific probing/measuring points ...
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6answers
805 views

Is there an implicit “unit of time” involved in electricity measurement? (e.g. miles per hour, kb per second, amps per ???)

I'm very new to electronics and I am going through what must be a common difficulty in grasping voltage, current, and resistance. I'll restrict my question to current as I suspect understanding that ...
0
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2answers
67 views

Question about sign

I need to answer this question using PSpice: It seems it's -15mA, BUT in the exercise, the current source is < (I understand it's + < -) in Pspice I set it to < as well, but there is - ...