Questions tagged [shunt]

Electrical shunt -- relating to a small resistance usually used to sense current. This is what your multimeter uses to measure current. This tag does not cover magnetic shunts.

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1answer
41 views

SMD "power" resistors : what constraints on PCB layout

I'm looking for current sens resistors. As those are rather big (and beeing for now the limiting element for my PCB size), I would like to stop using over-rated one and take some with "just" ...
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4answers
1k views

Why would a current measurement shunt design use 4 sense pins?

I am interested in low resistance shunts (tens / hundreds of microohms range) used in high voltage / high current setting. Typically, those are busbar-mounted shunt resistors like this one: The ...
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2answers
63 views

Do battery shunts (e.g. 500A/50mV) lower the final voltage on the system side by 0.05V / 50mA?

So I have this shunt in my power system connected just a few inches from the battery bank's final outgoing (to system) negative terminal. But I can't seem to find any data on whether or not these ...
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49 views

High Side, High Voltage Shunt Measurement with Differential ADC

I need to measure the high-side current out of an LED driver. The problem is that the output voltage can be as high as 250V. One solution would be to float an ADC and digital isolator just below ...
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3answers
111 views

Why is it important to eliminate ground-shift at the ground of a microcontroller?

I've asked a question about differential amplifiers and their uses in measuring current through a shunt. In doing so, lots of people advised me not to sense current on the low-side since that can ...
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6answers
2k views

Do you have to use an instrumentation amplifier to measure voltage across a 0.01 ohm shunt?

I was planning on implementing a current sense feature on the STM32 Bluepill to measure the current output of a solar panel (150 mA short-circuit current, 14 V Open-circuit voltage) using LM358 ...
4
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2answers
697 views

Where does one find the minimum voltage above the negative rail an op-amp can output in their datasheets?

I was planning on using a UA741CP (from TI) as a differential amplifier (to get a current value from a shunt resistor and then administer that value to the ADC of an MCU to avoid noise). However, I ...
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0answers
77 views

Shunt current measurement on phase

I measure the current of two phases (directly phase current, not the low side MOSFET current) of a PMSM motor and on some hardwares (2 of 10) I have issues with the phase current measurements. As a ...
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2answers
131 views

How to calculate the pulsating current flowing through a shunt resistor?

If the current flowing through the shunt (0.5 ohm) is in pulsating form (PWM with 50% duty cycle and 100 Hz frequency,) how do I calculate power loss through shunt in order to choose proper for ...
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2answers
862 views

-25mV output from op-amp with 0V input

I have this simple op-amp circuit used to amplify the voltage drop across an unknown resistor with a value between ~0 and ~20 ohms. The circuit works close to expected, but there is an offset - when I ...
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1answer
107 views

Why does the value of shunt resistor need to be very high for solar cell's greater efficiency?

In the circuit equivalent of a solar cell, shunt resistor is described as "The irregular polycrystalline lattice grain boundaries that resist to the flow of electrical current in the silicon ...
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0answers
52 views

Why do I keep blowing this current shunt amplifier?

I'm using an INA293B3-Q1 current shunt amplifier in the standard high-side configuration as shown below. The supply is a variable DC power supply (0-20V). Rsense = 1 mOhm. And, the load is a ...
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0answers
46 views

How do I determine the S-matrix for a combined series and shunt capacitors circuit?

I need to compute the S-parameters for the following two-port circuit, with combined series and shunt capacitors. simulate this circuit – Schematic created using CircuitLab I have tried ...
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1answer
41 views

High current thermal bypass

I am using a shunt to measure the current on a 12V system on a boat. Most currents are very low (under 4 A) but when using the starter the peak current reach peaks of 250 A. I've sized the shunt to 50 ...
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1answer
86 views

Current sense resistor - Should I consider self-heating contribution?

I am trying to implement a precision current sense amplifier. I am calculating now the tolerances introduced by the resistor. I know the maximum drop will be 20mV and I will use a 5mΩ resistor. Max ...
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2answers
2k views

Resistor in shunt regulator not following Ohm's law?

I was reverse engineering a power tool battery charger (21V SMPS) that derives its 5V rail from a simple shunt regulator, employing a TL431 programmable precision reference and a NPN transistor, as ...
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2answers
213 views

creating a differential amplifier for low voltages (current shunt)

I'm trying to create a "precision" fully differential amplification stage, to measure uA on a 10R shunt, and mA on a 0.01R shunt. shunt resistance values are set at those values for burden ...
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1answer
125 views

Shunt resistor after MOSFET and op amp to amplify voltage

I'm trying to figurate out how to measure current in circuit. I have idea to use shunt resistor but after connecting op amp on shunt I have some unpredicted measurements on output of op amp. I want to ...
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1answer
79 views

Best practice for paralleled four leg shunt resistors connection to a shunt amp, and best placement

I am using three WSK12161L000FEB paralleled together on a four layer PCB for a three phase motor controller (9 shunts total in design, 3 for each phase) From my understanding, a kelvin connection to ...
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1answer
69 views

Limiting current with a shunt resistor

For my project, I am using a 3.3V source to run two motors. If the motors pull more than 1A, then they have to stop. I was told to do this with software and hardware protection. As a programmer, I ...
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0answers
49 views

Fixed voltage drop (current and temperature independent)

simulate this circuit – Schematic created using CircuitLab Is there a clever way to create a fixed voltage drop say 2V that is not affected by current or temperature? Voltage stability should ...
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2answers
137 views

Voltage stability factor of voltage regulation circuits

Here a shunt voltage regulator circuit with two Zener diodes. One Zener diode Z gives the reference voltage at the comparator given by T1 for the feedback signal out Ra-Rb potentiometer. I can't ...
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1answer
208 views

Hall effect current sensor ACS712 for battery application

I want to measure the current of 12V lead acid battery for charger application. So mostly, I need bidirectional current sensing.The current measurement can be done using shunt resistor or using hall ...
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1answer
71 views

Killswitch: switchable high voltage path/shunt to ground without any additional power supply

I have a circuit with a high voltage source (rectifet 400VAC) (part of a capacitor discharge ignition.) High voltage should only be available if normal power (low voltage DC power supply for the rest ...
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0answers
37 views

Load/Shunt resistor value calculation for DC-DC Converters

I have DC-DC converter with rating -4KV and 1W. The unit supports current monitoring of output voltage. I would like to test the current monitoring using shunt resistor. What should be the rating of ...
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1answer
221 views

Very fast short circuit detection

I am working on a high current MOSFET switch project. I would like to implement short circuit/overcurrent protection, that would be fast enough to prevent MOSFETs from blowing up. In the actual ...
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2answers
108 views

Measuring high-side vs low-side current, different readings?

simulate this circuit – Schematic created using CircuitLab I'm measuring current consumption of several different handheld devices (calculators, flashlights, etc), at the [lithium] battery. ...
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1answer
51 views

How do you wire a transformer for multiple output and amperage?

I'm getting different answers watching the MOT (Microwave Oven Transformer) videos on YouTube. Some leave the shunt out, some leave it in, etc... I have a MOT and want to make a 12VDC power source ...
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1answer
91 views

How to measure shunt drop with an Arduino

I'm looking at a schematic like the following: simulate this circuit – Schematic created using CircuitLab I understand that this will be a very rough resolution as the drop will be in the 25 to ...
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0answers
47 views

Can I use two AD623 instrumentation amps on one shunt to cover broader current range?

I'm working on building a circuit with an ESP8266 module. I'd like to track its current consumption over time so I've cooked up a scheme to use a microcontroller dev board (Arduino or something ...
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2answers
332 views

What is the best way to parallel two shunt resistors using a switch?

What kind of switch in place of SW1 will have minimum amount of error in current readings? Max current is 10 A and we should be able to control the switch digitally. simulate this circuit – ...
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1answer
65 views

Determining the shunt resistance for DRV8301 BLDC Gate Driver

I am trying to study how to drive BLDC (Brushless DC) motors, and got stuck in the current-sensing part. I am using a DRV8301 Gate Driver IC, which contains with shunt amplifiers. My current ...
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1answer
100 views

Pulling down positive voltage to limit negative voltage current

Below circuit is the negative rail of a dual tracking power supply. How do I detect voltage drop on Node1 and pull down Node2 to limit the current without using an op-amp? Edit: I just want to define ...
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171 views
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138 views

Relationship between speed against armature current/torque in DC shunt motor

I do not understand why the graph is like this as below when we use flux control method of DC shunt motor Also, can I change the x-axis of this graph to be armature current instead since equation of ...
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0answers
102 views

Why does my multimeter report a tiny current through a shunted 9-V battery?

Why does my multimeter report a tiny current (microamps, if that) through a shunt resistor (e.g., 1.5 kΩ) or even a short placed across the terminals of a new 9-V battery? The multimeter and all ...
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2answers
90 views

BLDC 3phase motor. The resistor 5W 0.1 ohm to ground very hot when motor working at 250Hz

Any one help me on this my issuse. I have a BLDC 3 phase motor controler similar to this Schem here encloses. When the motor working at 150Hz everything is ok. But if it is works at 250Hz then the ...
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1answer
72 views

Does a wide-band, high-current, inline ammeter circuit already exist?

I have an application where I would like to measure currents up to 1000 A, inline, but am also interested in using the same circuit for a low current part of the cycle. The thought is that if I can ...
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1answer
49 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
112 views

Shunt Burn Issue

I've this schematic, where I'm blinking output bulbs (21W @ 12VDC). Rate of blinking is 85 counts/min. The wave comes to be of 700ms. On time 350ms. In this 350ms of On time, initially I skip 50~100ms ...
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1answer
190 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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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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1answer
311 views

Isolated DC-DC common mode choke without shunt?

I was reading a page on the Recom site (https://recom-power.com/en/rec-n-very-low-noise-filter-for-isolated-dc!sdc-converters-46.html?3) where they devised a filter setup to achieve very low noise on ...
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2answers
1k views

The issues of common ground with voltmeter and ammeters

Apologies if this post is, yet again, another noob in electronics. I have an engineering degree in audio but have newly found a passion for electronics and am teaching myself as I go. I am trying to ...
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1answer
274 views

H Bridge vs Half Bridge current sense

Are there any disadvantages in measuring H Bridge current only via 1 shunt resistor? Since it will be made by hand on a perf board the only disadvantage will be the possible longer wires that connect ...
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1answer
118 views

Low Side Current Sensing Grounding Question

I recently made a low side current sense circuit to test a power supply. It works well, but I am trying to understand the strange behavior that happens when I apply the negative lead of my probe to ...
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1answer
548 views

ADC Measure from source with higher voltage and different ground

I would like to measure the voltage of a battery that varies from 4,5V to 3V. To do so I'm planning to connect this source to a STM32F4 DISCO board and one of its ADCs, which will be set to a VREF+ of ...
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1answer
148 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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3answers
1k 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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1answer
268 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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