Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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42 views

2 mesh circuit giving me trouble. (steady-stade, mesh current method, dependent current source)

The task is to find Ic in phasor form. The circuit is in steady sinusoidal state. I used mesh current analysis and I got to that: I have no idea how to keep ...
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1answer
599 views

What is the formula for calculating the no load current of a 3-phase motor? [closed]

I am looking for the formula, not a rule of thumb. Is there a way to calculate the no-load current?
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2answers
188 views

How to connect multiple sensors to single PLC input?

Hello. I have a scenario where I have multiple PNP "error signal" from several sensors (let's assume 3 for now). If the sensor output is HIGH, then there is error. If the sensor output is LOW, then ...
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1answer
47 views

Current transducer - understanding of turns ratio connection

I'm using a LEM LAH 25-NP current sensor and I don't understand the recommended PCB connections in the table from the datasheet. I understand the first one, but what is with the second and third? What ...
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1answer
189 views

Why does the IC not respond (INA200)

The questions I have: Is the makeshift IC I use in the simulation a fair representation of the INA200? I assembled the circuit as shown in the picture (except for the current source and the LED) and ...
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2answers
1k views

Why does the measured current differ from the calculated current in this circuit?

I have the following schematic: Now I want to know the (more or less) exact current flow in my circuit. For this I did the following calculations: I = V / R I = 5V / 330 Ohm I = 0.015A = 15mA So ...
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1answer
59 views

Is that any best way to measure High side mosfet drain current?

To be specific, I am using 6 MosFETs (for ex. PSMN030-60YS) to drive an inductive load. I want to measure drain current of High-Side MosFETs. The way I am doing right now is by lifting the MosFET ...
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2answers
226 views

Electric current in mic

For a typical mic a singer uses in a concert, how much current is generated when the singer sings? The current transmitted from the diaphragm into the wire. What does the following specification tell ...
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3answers
143 views

Can I make a ammeter using a voltmeter and ohmmeter that would work in parallel to the device?

I had this small question today when working with an ammeter. Since an ammeter must be in series of the circuit, I had to constantly break the circuit to take current readings. Whereas, when using the ...
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1answer
97 views

How to measure current to detect motor stall on H-Bridge driven motor?

I have DC motor with a gearbox to transforms the rotational movement to linear movement and movie a pin back and forward. I need to know when the pin reaches the two positions: full back or full ...
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1answer
63 views

Understanding current transformer dimensioning, winding resistance and load resistance

I am looking at this current transformer. What I am trying to understand is the following: Can the burden/load resistor of a current transformer take an arbitrary value? What are the limits? Does ...
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0answers
101 views

How to measure currents between 0.1mA and 100mA? [closed]

Summary of question: I need to measure (using a microcontroller, not via a meter) currents between 0.1mA and 100mA, with a reasonable level of accuracy - say, to within 0.2 of a mA. My power supply ...
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2answers
132 views

In measuring relay contact resistance, should I use 4 wire measurement or calculate it using the voltage across the relay and current?

I'm reading mixed things online where a current from a typical ohmmeter is too low to accurately tell us the true resistance of the relay contacts. I've got a 30V 2.5A power supply, electronic load, ...
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4answers
734 views

Why not use a diode instead of a resistor for current sense circuits?

We're building a motor-drive circuit using an L6206 dual H-bridge circuit. The bottom side of its H drivers come out of a pin called \$V_{sense}\$, intended to be connected to ground or to a low-side ...
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1answer
75 views

What is the source of noise in this current measurement?

I'm measuring the current through a 100W motor with a 50A current sensor and I'm getting reasonably good data but there's also a fair amount of noise: This is the current sensor I'm using. It ...
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3answers
165 views

INA168 vs INA169 High-side current sensing

I have read the datasheets of the INA168 and the INA169 and can't see any difference, other than internal resistors value and quiscent current (25uA for INA168, 60uA for INA169). Those two were even ...
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1answer
105 views

Where did I miscalculate ohms law in my experiment?

I thought I finally had a grasp on how ohm's law works but when I set up an actual experiment, the numbers don't match up. To keep a long story short, I converted a computer power supply into a lab ...
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1answer
229 views

Analog input like in a PLC: Thermistor or 0-10V

Depending on the configuration, PLCs can often measure 0-10V, resistance or 0-20mA on the same set of screws. How to use the same screw terminal to measure resistance of an NTC element, voltages in ...
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1answer
88 views

Current monitor circuit not working

For part of a project, I am needing to monitor the current draw of 4 low power loads simultaneously. I like experimenting with circuits and I found one online in a TI application note (AN-31 page 35) ...
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1answer
165 views

High side current sensing

I want to sense 30 amps of current using op amp in high side. I know that there are many dedicated current sensing amplifiers for this purpose. But I'd like to try it with an op amp. I have tried high ...
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1answer
217 views

Measurement of current with hall effect sensor

I have a setup using 3 hall effect current sensors and my goal is to measure the DC current flowing through cables. The sensors are HSTS016L. I attached a picture of the manual. The sensors have 4 ...
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1answer
89 views

When I checking the hot terminal in the socket, multimeter shows the current through me?

I set my multimeter in AC voltage measurement, connected + wire of multimeter to the hot terminal of the electrical socket, and take - wire in my hand. Now it measures the voltage. This procedure ...
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2answers
118 views

Measure volt, amps, watt and kWh of an external 12 V DC system

I saw online some cheap hardware ~10$ that can measure volt, amps, watt and kWh and display the results on an LCD screen. I could buy and plug these on my 12 V solar panel system to monitor it. (5 of ...
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2answers
100 views

Pulsed DC current measurement using arduino and shunt resistor

I am currently working on a project ( to develop a constant current pulsed DC supply) in which current has to be measured using Arduino's analog input (Upto 20A) passing through a variable resistance ...
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1answer
78 views

AC current measure using CT, 10-bit 200 ksps (mcp3008) or 12-bit 100 ksps (mcp3208), which is better?

First, sorry for my bad English I try to build my own wifi energy metter using esp8266 and mcp3208. My electric knowledge is very simple, now my design use mcp3208 to measure AC current from CT, but ...
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3answers
219 views

Clamp multimeter RMS current measurement, AC versus DC confusion

This question doesn't relate to a specific meter, I am using AMPROBE AMP-220 manufactured by Beha-Amprobe. I believe am an experienced engineer but only in the digital world, not really in power and ...
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0answers
107 views

ST VNH7070 current sense specification

I don't understand the way ST specifies their current sense pin in the VNH7070 H-bridge motor driver, see the datasheet below. How do I know what the current Isense will be? Why does the voltage ...
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1answer
38 views

What is the predictable difference of the voltage drop between the V+ and V- lines on a shunt resistor?

I am making an electronic speed controller, and the half-bridge driver I am using has a built-in overcurrent protection feature. In order to utilize this feature, I have to supply the pin (a ...
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3answers
291 views

Current measurement with shunt

I need to measure pretty high currents (maximum 100A) flowing from one battery to another. I came up with a solution involving the measurement of the voltage drop across a shunt resistor. The supply I'...
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1answer
33 views

What's the easiest way to implement portable current measurement for a ~200W dc motor?

I'm tinkering with an electronic skateboard build and I'm looking for a way to do some current measurements "on-the-go". What's the easiest way to implement this? It wouldn't be a part of the final ...
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4answers
272 views

Understanding “Current Draw” in terms of “Ohm's Law”

I'm having trouble understanding Current Draw as it relates to Ohm's Law (V = IR). I have a power supply rated at 5V and 500mA. I'm trying to power a string of LED lights. According to my ...
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2answers
117 views

Arduino + Current Sensor -> Not always working

I am trying to measure power consumption of devices by using an TA12-200 power sensor with a Arduino Uno board. This sensor is using a 800 ohms resistor and a 1:2000 ratio. My measure to get mAh ...
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0answers
55 views

micro controller cant able to sense analog value (ADC input) from op amp output

I am trying to sense the current in my motor controller using shunt resistor and an op amp. Opp amp amplifies the voltage drop of the shunt resistor, multi meter shows the output voltage good. But ...
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0answers
183 views

measure 4-20 mA and also power from loop powered

we know to give a command to an actuator in instrumentation we use 4-20 mA loop power. for reading this 4-20 mA I used the circuit below.so the problem is if my circuit only consumes 3mA, how should ...
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2answers
364 views

Full wave rectification by opamp

I am trying to read a current waveform from a shunt resistor series with the power line. Using a full bridge rectifier, I got the following waveform: The waveform was sampled every 2 millisecond ...
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1answer
48 views

Current readings of Ammeter

I was trying to solve this problem (number 27) and as per the KCL equations I am getting that an infinite number of Ammeter readings are possible. I used KCL after taking the outer loop as the ...
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0answers
352 views

Unstable speed with A4964 BLDC controller

I am using an Allegro A4964 for controlling a BLDC micromotor. I have tuned the PID and all available parameters according to the documents available from Allegro. Problem: In the control modes I ...
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4answers
149 views

LTspice - analyze current with varying resistance

I would like to graph current from V1 over varying resistance instead of voltage. Is there a way to do this?
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1answer
48 views

Best method to determine current in ESR meter

I've recently found the need for a ESR meter(My daughter and her boyfriend brought me 8 broken LED/LCD TVs and 6 have power problems). I also decided to go all out and build a full blown ESR meter. ...
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2answers
49 views

Rogowski coil current rating

Is there any relationship between sensitivity of rogowski coil and voltage rating of coaxial cable with it. For example if I just have the sensitivity of the coil and spec of coaxial cable, is there a ...
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1answer
75 views

Current calculation for circuit diagram

I am new to this field and need help calculating current I2 through voltage source 2. U1=1V U2=3V R=10 Ohm Unfortunately I have no clue how to calculate this. Would be so thankful for help!
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2answers
78 views

multimeter, current measurement (beginner)

From this little circuit I try to calculate the current for Ic, Ib, Ie. For Ic , I put the multimeter on 20mA and positive wire connected to 10A and I got 0.01 ... 10mA ? for Ie it is the same (Ie = ...
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3answers
49 views

How to measure current in very low duty cycle circuit with DMM?

My circuit has 4Hz 50% duty cycle. How do I measure the average current using a DMM? I have a Fluke 87 DMM. It has an average setting but for 100 ms which less than one complete duty cycle. My ...
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1answer
65 views

How to connect INA321 in order to measure current across a resistor?

I need to measure control over a resistor using an instrumentation amplifier. I am using INA321 but for some reason, it does not work. Here is my circuit: In this circuit, the output voltage is ...
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1answer
158 views

Switch current sense resistor: series or parallel?

I am building a device that measures current in various ranges. For this I want to switch in different current sense resistors. To do this I see two ways: the resistors in series or the resistors in ...
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2answers
192 views

Real-time measurement of motors' current draw for a mobile robot

Found an Arduino-compatible Voltage-Current Sensor; it could remove the need for a separate voltage sensor. Is there a more recommended method to continuously and simultaneously measure the current-...
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1answer
137 views

AD8217 High Side Current Sensor Output at Low Currents

I am using an AD8217 high side current sensor to measure currents up to 20A. It works as expected when testing with lower currents and sense resistors of 1\$ \Omega \$ and 0.3\$ \Omega \$ and ...
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4answers
2k views

Why are current probes so expensive?

I notice that clamp-type current meters range in price from a few dozen dollars to a few hundred, but current probes for oscilloscopes cost significantly more, with many close to $1000 and some well ...
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3answers
602 views

How Much Current is Usually Used with IR Transmitting LEDs, in Remote Controls?

If you take various Remote Controls from your home, such as for a TV, Audio System, TV Box, etc, and measure the current that is supplied to the IR LED in the remote, what would be common current ...
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1answer
331 views

Resistor values on a 12v 10a circuit with LT3045 LDO

I am currently working on a project that aims to provide 12v 10a in the final output. I am quite new to EE and wasn't quite sure if I have choose the correct resistors value as highlighted in the ...

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