Questions tagged [current-measurement]

Measurements of the current flowing through a circuit

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1answer
28 views

High current usage from LDO when not hooked up to VIN

I built a circuit powering an ESP8266 MCU from an MCP1811 LDO so I can use a 5V logic level. The MCP puts out 3.3V as desired by the ESP. The circuit looks as in the data sheet example: Assuming the ...
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1answer
88 views

Low side current sense output waveform

I am trying to build low side current sense amplifier for my motor drive (1 kW BLDC trapezoidal control.) Before that I get confused with the current waveform of BLDC drive in low side. My application ...
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23 views

Calculate average current draw for instantaneous loads

I have a battery powered project with the following statistics: sleep current: 1.5uA activity A: 500uA average in 10ms interval (peak current is 1mA) activity B: 1.2mA average in 20ms interval (peak ...
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53 views

AC Power measurement ( digital sampling)

i want to measure AC power and i want to know what is the best and safest way to digital sample AC voltage and AC current? For AC voltage: We can use voltage divider and feed it to ADC with reference ...
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1answer
28 views

Power Supply Current Display [closed]

Is it possible that my power supply is not able to show on its display the full current is being delivered to the circuit? I am driving a couple of solenoids and if I measure the current with a ...
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1answer
58 views

Measuring soil moisture and using a vintage DC ammeter as the indicator

I have a vintage Weston Model 506 DC ammeter (it has a range of 0 to 20 amps) that has been sitting in my office and I think it would be interesting to use it as a soil moisture indicator for a (long ...
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1answer
40 views

What is the best way to measure and record the power consumption of a servo motor accurately?

I can obtain the rotational angle and velocity of a servo motor. However, I cannot obtain the current nor torque while the motor is turning. What is the best way to measure the power consumption of a ...
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1answer
46 views

AC mains current monitoring

I'm designing an ATmega328 PCB with an optoisolated TRIAC controlling a 100W (~ 0.5A, 230V, PF = 0.98) load. I'd like to monitor the current with the processor and report an error if the current drops....
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1answer
45 views

Isolated DC-DC Converter screws up ADC

I am developing the automated test system depicted in the following picture. The system receive commands and returns result data via Bluetooth to a remote computer DK52 is used to fine tune the ...
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1answer
42 views

Which current types can be measured with a Shunt?

Which of the following current types are typically measured with the help of a shunt resistor? DC AC Impulses (4/10 us, 8/20 us, longer impulses > 500us?)
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1answer
72 views

Circuit distorting AC signal from CT

Below the 60Hz signal from the CT only with the burden resistor connected: When I connect it to the opamp circuit, this is what it becomes: Some points about the circuit below: x1,x2 - z1-z2 are ...
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2answers
60 views

How to calculate the current / power consumption of instrumentation amp with op amp as an impedance converter at REF input

I have a measuring bridge and want to connect it to an ADC with an AD8227 instrumentation amplifier (Datasheet). For the reference voltage, I have connected a voltage divider to an LP358 as an ...
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1answer
48 views

Single shunt with multiple current sense amplifiers vs using multiple shunts

I would like to turn an Arduino clone into a current meter that allows me to measure the the power draw of a sensor node which has sleep and active modes. The sensor node's supply voltage is in the 4-...
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1answer
55 views

Why Does Relative Magnitude of AC Current Waveform Decrease Based on Phase Ange?

Background First off, I apologize if this is comparatively basic theory. My primary profession is firmware and I only do electronics as a hobby. I am attempting to design a power supply for a ~450W ...
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2answers
1k views

Is it practical to use relay contact resistance as a shunt?

I'm driving a DC motor and in its path is a relay with approximately 100m Ω contact resistance, can I use that resistance as a shunt resistor to measure the motor current? I don't want to measure the ...
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2answers
76 views

How to measure the On/Off current ratio in TFETs and MOSFETs

I saw the conventional understandings other questions: MOSFET ON and OFF current As I know, the off current is not zero, however very small, in the cut-off region. When we discuss TFETs, one of the ...
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1answer
40 views

How to avoid negative voltage on MCU pin from RCV420 converter?

I am working on a circuit to convert 4-20 mA signal to 0-5 V to finnaly read with an analog input of an MCU (PIC16F886). The IC I'm using to convert the signal is the RCV420K which works fine. On the ...
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1answer
89 views

Will a light bulb work the same on a car battery?

So I have an incandescent light bulb that is rated for 100W at a voltage of 220V. So, I calculated that the resistance of the bulb is 484Ω. I wanted to connect it to a car battery (24V). I know most ...
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1answer
75 views

Can't find non-invasive dc milliamp sensor [closed]

Why is it impossible to find a non-invasive DC current transformer in the milliamp range that is split core (can open and close around wire)? I would like to sense when a wire is carrying current or ...
0
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2answers
60 views

Detecting very high voltages

I work for a plastics molding company and we manufacture containers that we need to verify do not have holes in them. I am looking design a fixture that will apply a very high voltage (about 15-30KV) ...
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0answers
48 views

Allegro ACS71020 unable to read voltage SPI register

Hi I'm trying to read from the registers of the ACS71020 over SPI, but I can't seem to get any values other than 0. The only time I am able to get anything other than 0 on the MISO line, is on the ...
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2answers
90 views

Measure DC current with current transformer

Is it possible to measure DC electrical currents with some type of split core current transformer? Or it is only for varying currents? EDIT Considering a zero-flux CT, could someone show me the basic ...
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3answers
115 views

Current sense resistor for high voltage

I have a 5KV DC output from a Cockcroft-Walton multiplier. The current is around few microamps as per the simulation. To prevent discharge, the 200Mohm resistor holds the voltage of the Cockcroft-...
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1answer
75 views

Can you please help me solve this circuit?

So I'm trying to solve for \$V_n\$. the way I solved it is by: $$4I_x5+ 15I_x+ 5I_x= 15$$ $$I_x= \frac{15}{40}$$ then \$v_n= 7.5\$ What do i do wrong ?
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1answer
172 views

Charge, Voltage, or Current? What can be measured with the highest SNR?

Suppose I have a Faraday cup and a certain number of ions hit the detector. What is the highest signal to noise ratio way / circuit to measure this... does one measure the charge (coulombmeter), ...
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1answer
85 views

Where did my thought go wrong (electrical circuit )

The circuit on the right has two identical diodes, D1 and D2. These diodes have a scale factor n = 2 and a value of saturation current IS = 9nA. The currents in the diodes are as shown. Use the ideal ...
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0answers
35 views

Will the measured powers & energies of two 120V circuits == that of the 240V circuit?

I'd like to design a circuit using the STPM34 (2 channel power meter) that can measure either the power and energy delivered on two separate 120V circuits (one circuit Red Wire, other circuit Black ...
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1answer
56 views

Building a Bio-impedance system

I currently have a project that has integrated sensors to monitor human health and related biomarkers, my domain is human-performance so giving athletes the tools to get better at their respective ...
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2answers
77 views

How to measure small AC currents from mains?

I want to measure AC current from the mains connected to an isolated source - such as a single 10 watt bulb. The standard multimeter measures the current only in DC, so I needed a device that provides ...
0
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1answer
49 views

Sensors - How to convert 4-20mA output to temperature and pressure values?

I'm dealing for the first time with two sensors, of pressure and temperature. Both have output of 4-20mA, then I'm using a 47 ohms 1% to convert to voltage. When flows 20mA, 20mA * 47 ohms = 940mV, ...
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1answer
51 views

Can these small Hall-Effect Current Sensor Modules really handle 30A?

These don't look like the could reliably handle 30A to me. The terminal block is small, the chip is tiny. Please help me understand what the considerations are when sizing components & traces for ...
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46 views

DRAM Self-Refresh not the Lowest Power Mode

I have a DDR3L Samsung DRAM on my Laptop. Based on page 23 of its datasheet, IDD6 or the ...
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2answers
43 views

ACS712 overcurrent consequences

I have a motor that's rated at 28A. I want to monitor the power it's drawing so I got an ACS712 in its 30A variant. Knowing the voltage and multiplying by the output I get the power. But what happens ...
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1answer
62 views

What is the minimum PWM frequency that LT1999-10 can capture with smooth output settling?

I am referring data sheet of LT1999-10, My PWM signal is 100Hz duty 5% resolution 8 bit I have a doubt, Data sheet - 2MHz bandwidth Is this IC able to capture 100Hz PWM signal? will output of IC ...
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0answers
40 views

Is it possible to measure pwm load current using opamp based high side current sensing?

I am referring this app note, hope to use as unidirectional current sensing for a PWM load PWM load - load is a resistor, PWM signal - 100Hz, 150V. Load current 18mA Duty 5% (PWM resolution 8 bit) ...
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3answers
2k views

How OPA333 withstand 400V bus without burning in this current sensing application?

I went through following app note, where OPA333 is used in 400V bus current sensing application, also i have seen current sensor which have term called common mode voltage, which is specify the max ...
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0answers
35 views

Library file error while using a Third party component( INA138)

I want to use the INA138 as a current sensing amplifier but its symbol is not available in Ltspice so I downloaded the .lib File from https://www.ti.com/lit/zip/sbom140 here. I then opened the file in ...
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1answer
60 views

Op Amp High Side Current Sensing

I'm trying to build a high-side current sensing circuit with a differential op-amp which can be seen below: The LT1006 is actually an LM358 IRL(I know it's a peanut op-amp, but it's what I have ...
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2answers
47 views

Voltage in a circuit with variable resistance and diode in series?

I came across some examples to calculate the current in a circuit with diode and resistance in series. Consider the circuit below: Current was calculated as follows: I = (9 - 0.7)/R1 Does that mean ...
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1answer
66 views

How do I know that enamelled wire is actually conducting the current?

I am trying to make an electromagnet so I bought magnet wire to wrap around an iron core. I am pretty sure that there is a current running through the copper wire because I attached an alligator clip ...
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2answers
56 views

How to calculate current drawn by microchips, transistors and diodes? [closed]

So far, I've dealt with only devices like resistors, capacitors and inductors. Calculating the current drawn by these devices is very simply by using the formulas I read in my Physics textbook (e.g. V ...
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1answer
73 views

Why INA293 provide discontinuous reading on low duty PWM signals?

INA293 has 110V common-mode voltage 1MHz gain bandwidth my signal 90V, 100Hz PWM, 10%-25% duty, load current 30mA max shunt resistor 5 Ohm the gain of ic 20V/V Vout = 30mA x 20V/V x 5 Ohm = 3V i use ...
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33 views

How do I conduct an experiment to find the discharge curve of a lithium ion battery?

I want to conduct this experiment with a multimeter only. What sort of load do I put? I used a Sony Li-ion Np-BPL battery model and after full charge, I put the battery across a load of 1k Ohm; ...
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3answers
788 views

Why cap across shunt resistor, input bypass caps and small resistors on current sensing inputs?

I want to build a sensitive current sensing circuit using shunt, and since I also repair MacBooks occasionally, I have some contact with the schematics of real working expensive devices (although ...
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2answers
43 views

Help needed to determine inductor material/turns needed

I am trying to formulate a circuit to sense current in a standard US 120V AC power line. I'm planning on using an inductor as a current transformer to sense current flow and allow a microcontroller ...
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1answer
51 views

Microamp-milliamp Measuring Circuit: will my circuit work? Feedback/Advice

I'm developing a device which must be able to measure milliamps and microamps on one of its lines (down to 1 microamp, but also clearly seeing if it's less than 1uA). It's going to be DC of different ...
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1answer
53 views

Measuring Current in Coax Cable Using Clamp on Current Probe

I once again find myself needing to measure the RF current in a coaxial cable. The signal in question is a high power (100W-1kW range) signal which is a stepped waveform with a 5MHz fundemental with ...
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0answers
35 views

Current / power measurement using ACS71020

I am having some hard time in understanding and comprehending the value for ACS71020 current and power measurement. In the manual, rms_avg_1 and rms_avg_2 has been mentioned stating that "The ...
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2answers
59 views

Voltage drop of a PWM signal

Hello so i have a microcontroller that is driving the following circuit: Both the MCU and the circuit are powered by a 5v power supply, when PAD_PWM and PAD_PWM_return are not shorted ore there is no ...
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2answers
66 views

Reading +/- 12V with 3.3V micro

I have 3.3V micro and +/- 12V square wave input I need to measure. As my MCU can only read 0 to 3.3V, I would like to ask the best way to "translate" this +/-12V signal into 0 to 3.3V. I try to ...

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