# Questions tagged [voltage-measurement]

Act of measuring voltage

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### Measurement of PID circuit intrinsic noise

I want to perform a dummy test to compare different general purpose PID circuits. I am specifically interested in the RMS voltage noise of these PID circuits independent of the system they are used to ...
• 527
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### Measuring voltage of a terminal when the reference paths that become different from switched using a MOSFET

I am designing a Power Monitoring and Protection board that is going to sit in between a 5-Series (~70V) Lead Acid Battery and a load. This board has a Energy Monitoring IC from TI - INA237AQDGSRQ1 ...
113 views

### How to measure the voltages of a three-phase generator

I have a three-phase generator and I want to measure the voltages of each of the phases, but I don't have a neutral point. How would I connect the phases to an ADC, and how would I make a voltage ...
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57 views

### How to adjust this circuit to allow measuring of negative voltage beside positive voltage through microcontroller?

I am using the following circuit to measure DC voltage that is up to 18V, and I was wondering if there's a way to make it able to measure negative DC voltage down to -18V as well:
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131 views

### Mathematical relation of RMS to PK-PK for noise

RMS is root mean square, peak to peak is the difference between peaks of a signal. In the video and other places, they say the 1 mVRMS = 6.6 mVpk-pk. The reason is 6.6 standard deviations covers 99% ...
107 views

### Large channel count (100+) measurement solution? [closed]

I am a mechanical engineer by trade, so please correct my assumptions if they are wrong. I'm designing a test rig for my company's electrolyzer design. The electrolyzer will have anywhere from 128-200 ...
91 views

### Simple circuit analysis question, voltage across an unknown component

Question: Joe was debugging part of an experimental apparatus, probing around with his voltmeter. Part of the apparatus had two obvious resistors in series with an unknown element, as shown in the ...
126 views

### How do multimeters measure very high resistances, and how does (human) body capacitance affect it? I would like a technical answer

Technically speaking, how does a multimeter (Fluke 289 in my case), measure impedance (resistive only), and why does touching a metal case you are measuring with your hand change the reading "...
75 views

### How can i make this idea work in PCB?

Assume i have a source of energy (voltage source), i want to sense the voltage and current of this source and transfer this analog information to an ADC (arduino nano) thus i have to make the voltage/...
55 views

### How to Read Unipolar Square Waves on TRMS Multimeter

I'm trying to switch from reading my high-voltage unipolar square wave signal from a benchtop oscilloscope to a handheld multimeter, but I don't understand why my multimeter is giving the voltages it'...
172 views

### How do I create a circuit to reliably calculate a range of unknown resistances?

I'm designing a low power circuit which serves to determine the unknown resistance across a 16 channel sensor. So far the results are bit subpar. The resistances are a function of a different applied ...
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### Ground connection of power converter and MCU

I've designed an AC/DC power converter PCB, with input, and output voltage sensing, but I have problem connecting it to microcontroller board, i'm using F28379D launchpad as the microcontroller. I ...
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119 views

### How to measure battery voltage during charging?

I have a slight confusion regarding the battery. Suppose I have to charge a battery of initially 12V to 14.2V (full charge). My charger has open circuit voltage of 15V. When I connect it what voltage ...
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1 vote
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### Voltage Divider + Unity Buffer as a power supply

I'm working on an application where I need to step down a 3.7V LiPo down to a 1.0-1.5V for an embedded device that takes AAs (effectively an AA-to-LiPo conversion kit). In order for "low battery&...
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### Constructing the voltage as a function of time for a circuit with a capacitor and resistor under a current source

I have a circuit as shown in the image. I want to derive the formula for the voltage V(t) as a function of time; when a constant current source is applied.
31 views

### Brown outs with Nordic Instruments PPK2 power profiler

I have a circuit that I know works with 2 AA batteries that are nearly dead (1.4 volts total). I want to measure the current consumption of the circuit using my Nordic Instruments PPK2 meter. The only ...
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120 views

### Why is my oscilloscope math mode showing an RMS voltage in gigavolts (unexpectedly high value)

I'm experiencing an issue with my Rigol DS1202 oscilloscope. When using the math function to measure the RMS voltage of the difference between two channels (A - B), the RMS value is displayed in ...
1 vote
103 views

### How to offset a sinusoidal voltage centered at 0 V for power grid measurements

I am trying to take voltage and current measurements from the power grid (120V 60Hz) and process them with a 3.3V based digital signal processing board (TI F280049C launchpad) I am using LV25-P and ...
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1 vote
105 views

### Detecting and measuring AC line voltage with an optocoupler

I simulated the circuit shown below using MultiSim and obtained some interesting results. The simulation suggests that you can accurately reproduce the AC line voltage from the input to the output. ...
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### Is it safe to use a battery charger with an output voltage higher than the battery voltage? [closed]

I apologise in advance for any erroneous or obvious points or terms I may use. I have a Remington beard grooming razor, which originally contained a 1.2V 700mAh NiMH rechargeable AAA battery, which ...
59 views

### What does an accuracy of 0.1% + 20 mV mean in a power analyzer's data sheet?

I need to know the measurement accuracy of Keysight N6705C power analyzer. I came across this document (N6700 Modular Power System Family.pdf) that states the error in terms of a percentage plus a ...
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### Confusion around 3-wire/4-wire three phase voltage sensing

I'm trying to understand the voltage sensing setup when measuring three phase voltages in a 3 wire system (like Delta with no neutral) or a 4 wire system (like WYE) or Delta High leg (delta with ...
31 views

### Understanding Voltage Read in Voltage Divider for NXP S32K118 Microcontroller ADC

I am having a bit of a hard time understanding the voltage read in the voltage divider that is being an input for an ADC to an NXP microcontroller, S32K118. Below is the schematic of the circuit. ...
195 views

### Average filter of a signal in C

I'm having troubles designing a code for an ADC measurement, I'm trying to read a signal that comes from charging a battery with pulses, so the signal will be something like the photo uploaded. ...
104 views

### How does a multimeter measure small voltages without being connected to ground?

I have a multimeter powered by a 9 volt battery. I put it in AC voltage mode that allows me to measure 0.001 volts. I have the red probe connected and the black probe (common / ground) detached. When ...
26 views

### Forward Voltage diode for a fixed current and different temperatures

I should measure forward voltages of a diode for different temperatures and a fixed current. I have a Keithley 2602A. Should I do a current source circuit?
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1 vote
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### "50 Ohm" vs "50 Ohm terminated" in ACV accuracy specs

In the accuracy specifications for an AC voltage measurement with a Keysight 3458A, there is a distinction between source impedance of "50 Ohm" and "50 Ohm terminated" for the &...
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### How do I properly wire an SL-510-SS pyrgeometer to measure its internal thermistor resistance?

I've acquired an SL-510-SS pyrgeometer and am having trouble wiring the internal thermistor. The manual gives the following description: The manual also provides the following diagram: I've ...
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### High current/voltage power monitoring in small form factor

I am attempting to build an I/O board to integrate with software I have running on a Raspberry Pi 4. I need the board to monitor voltage and current (power would be a bonus) on 8 circuits running ...
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1 vote
110 views

### Microcontroller that can do 10 UART? [closed]

I am currently working on a project that would require a total of 10 UART (rx and tx pins) to run 10 PZEM-004Ts for different electrical lines. I am thinking of using an atmega 2560 because it has ...
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### Coax cables, impedance matching and BNC extensions

I'm trying to understand how to do proper measurements with a Voltage Differential Probe ( TT-SI 9010. This probe has an output impedance of 50ohm and has a BNC (It doesn't specify it in the data ...
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### Measurement of high voltage

For research lab work, we use a high-voltage generator to create one pulse with a low intensity (< 4 mA). The voltage range is variable from 100 V to 3000 V and the FWHM of the pulse is ~1 ms. The ...
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### Why might my circuit's measured voltage drop when I add more load to it?

I have one of these power supplies: I also have an MCR-4V data logger: If I connect wires directly from the power supply to the data logger (red to red, black to black), then the voltage output on ...
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### On working principal of the low DC voltage charger of this certain behavior

How is the simple working mechanism or principal of the DC stage of a typically low DC voltage, ~ 5V, charger with the behavior: if a MM simply testing its voltage it gives 0 volt if a battery is ...
243 views

### Circuit for averaging AC voltage

I made a rl multivibrator with square wave output. The ton and toff of rl changes with magnetic field around. Normally the wave is symmetrical but on passage of magnetic flux, the pulse width changes ...
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210 views

### How to check the high voltage of a electrostatic device?

I want to build a device with two metal plates which needs to have 3000 VDC between them. The way that I am thinking is to use a ferrite transformer from a 9 VDC transformer with a transistor that ...
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### How to perform Kirchhoff's Voltage Law on an open circuit? [closed]

I am wondering how to perform KVL on an open circuit. For V_s = 10V, I have determined the V across R2 to be 10 Ohms but am confused about R3. The algebraic sum of the voltages around any closed loop ...
51 views

### KY038 sound sensor: Voltage to SPL

I'm writing code to measure frequencies with a KY038 microphone sound sensor. It uses an LM393 voltage comparator. How do I convert voltage to sound pressure level (SPL)?
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### Measure transformer real power

I’m new at making transformers myself, and the ones that I designed had the correct output voltage, and when they were connected to batteries (previously rectified), they give me a an approximate of ...
65 views

### What type of galvanometer is in this picture?

Does anyone understand the galvanometer in Faraday's experiment to the left in the picture below? How does it operate? It looks like it uses a magnet and some xy axis the needle swings over or maybe ...
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4k views

### Are there any tricks for measuring high voltages (~1000 V) efficiently?

The simple way to measure voltages above VDD is to use a resistor divider. However, once you get into the 100s of volts these dissipate significant power. For example, one of my current designs ...
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### Uncertainty for measuring a resistor

I am trying to calculate the uncertainty of a measure on a resistor. The expected value of the resistor is 45 mΩ. For measuring the resistor I used the two following instruments: SM500-CP-90 Agilent ...
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### How to extract voltage and current from this real-life circuit (with resistors)

I recently measured some voltages across two resistors as you can see in the images below. I used a triangle wave as voltage source and measured the voltages across the resistors with an oscilloscope. ...
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### Output voltage not changing with a constant current driver

If I attach a voltmeter to the output of this constant current driver and lower or raise the input voltage (100-230V,) the output voltage remains constant at 56V. Should it not fluctuate between 40-...
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### Why is the voltage across the LED negative, when the entire drop is positive?

I was changing the control board of my 3D printer. When testing the heatbed, I saw that the LED wasn't glowing (as with the old control board), when the heatbed was turned on. So I investigated with ...
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### Which is the best method to measure AC voltage?

I am trying to make a UPS circuit. I need to have a high speed measurement for the input AC voltage (220 Vrms) (in order to know whether to turn on/off the inverter). I had tried using this circuit: ...
69 views

### Which filter to use when measuring the voltage power line, common mode filter and/or differential mode filter?

I'm using an 78M6631 IC for three phase metering. For voltage measurement, the datasheet recommends a voltage divider. Researching through internet is recommended to include a filter, I don't get when ...
162 views

### Isolated voltage measurement circuit or sensor

Which circuit or sensor can measure a voltage range of 24 V DC (the power supply for a motor)? The circuit is fully galvanically isolated from the ESP32 used. Does anyone have any ideas on how to ...
1 vote