Questions tagged [voltage-measurement]

Act of measuring voltage

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-2 votes
0 answers
26 views

How to measure change in TDS instead of absolute TDS through a TDS sensor?

I am using a total dissolved solids (TDS) sensor to measure TDS in an evolving solution system. The code below works fine to give the absolute TDS, but I would like to note the change in TDS over time....
2 votes
1 answer
39 views

Do I need a precise voltage reference for my ADC if the what I am measuring shares the ADC voltage source?

I'm trying to design a basic measurement system using some phototransistors and ADCs to measure light absorption via a voltage drop. I've attached a schematic for a quick and dirty representation of ...
1 vote
1 answer
132 views

Cheapest way to detect low voltage of a battery

I have 29V battery which drops to 24V at about 30% capacity. I want to detect when the battery goes lower than 24V and generate a 12V signal. (I have 12V auxiliary supply for lights etc) Since I'm ...
1 vote
1 answer
67 views

Is it possible for two MCUs to monitor the same analog voltage signal?

I was thinking about tying two separate microcontroller inputs together so that they would be on the same node and monitoring the same voltage signal. Both basically doing the same thing (analog to ...
3 votes
1 answer
93 views

How to measure voltage with a floating supply?

In the example below, ground of a dual supply is referenced to +Vout. Assuming we have a MCU connected to VCC and +Vout, if we then try to measure the voltage at +Vout with the ADC, we're basically ...
0 votes
2 answers
177 views

Measuring battery voltage in a PV scenario with an MPPT charge controller with inverter

I'm doing a PV project with WiFi-enabled statistics. I'd like to monitor the power coming in and going out, the battery charge level, and the estimated battery charge and discharge time. I'm designing ...
0 votes
1 answer
252 views

Using an arduino to measure a voltage in the range of 0-20mV

I'm building a control panel for an old altitude training machine and I need to measure the output of an oxygen sensor with an arduino. The oxygen sensor (medical oxygen sensor OOM202) is a micro fuel ...
0 votes
2 answers
63 views

Using transformer secondaries for audio amp

I have a old transformer out of an audio amp and want to repurpose it for another DIY amp project using the LM3876. There is a 5 pin connector for the secondaries. I checked voltage potentials across ...
0 votes
0 answers
46 views

Current measurements for a DC motor being rectified when in reverse direction (differential low pass filter implementation)

Recently for a project I've been trying to capture voltage and current characteristics for a DC motor. To measure current, I'm using a single resistor (R1) in series with the motor, and feeding the ...
-1 votes
1 answer
36 views

Confusion of measuring the stator voltage of induction motor [closed]

I'm new to inverters and the only way I know how to measure the stator voltage of induction motor is to connect the multimeter to terminal of junction box. So could anybody please elaborate more about ...
-2 votes
0 answers
70 views

Improved design for high precision resistance meter

I'm designing a high precision resistance meter, which will measure the change of resistance of a given remote resistor, which is not placed on the circuit PCB, against temperature. The target is to ...
3 votes
4 answers
647 views

AC volt meter using an Arduino not giving steady reading

I am trying to make an AC voltage reading system according to the circuit below which I found online. My voltage is coming out cyclical - why is that? Is the capacitor perhaps to blame for not ...
2 votes
5 answers
519 views

High precision resistance meter

I'm designing a high precision resistance meter, which will measure the change of resistance of a given remote resistor, which is not placed on the circuit PCB, against temperature. I want to do this ...
5 votes
1 answer
113 views

Why am I getting inconsistent voltages at op-amp's inputs in a simple DC amplifier?

I'm new to circuit design and am unable to figure out why I'm getting inconsistent voltage measurements under certain circumstances at the inputs of an op amp in a very simple non-inverting DC ...
5 votes
5 answers
2k views

How does a voltmeter determine voltage?

For example, using a battery. Does the meter place a small resistance in line with the two terminals, then measure current and solve for V using V=IR? I’m looking for the general theory.
3 votes
1 answer
324 views

Where does the 1V voltage come from?

I have a four PLC with many digital I/O connected similarly to the schematic below. If I use multi meter and measure the voltage between the two points in the schematic, why is it showing 1V? Isn't it ...
0 votes
2 answers
91 views

Arduino as a voltmeter

I need to read DC voltages between -2.5 V and 2.5 V with Arduino. I have read that an op-amp in inverting configuration (below) can be used to add a DC component. Therefore, I have thought about using ...
0 votes
2 answers
427 views

Capacitive Voltage Divider and Discrepency in Output Signal

Background I designed a capacitor voltage divider for the purpose of measuring the voltage step up of a resonator. Before I measure the voltage step up I wanted to measure the voltage divider ratio to ...
1 vote
1 answer
50 views

Is it safe to connect an oscilloscope to a Power over Ethernet line?

I have found that PoE uses isolated power delivery. If I splice into my ethernet cable, will I be able to hook up a scope to one of the 8 lines inside safely without frying anything? The scope and the ...
1 vote
1 answer
1k views

ACS71020 Connecting and reading voltage properly

I am using an ACS71020 3.3 V I2C version hooked up to an ESP32. I have connected the IC as proposed in the datasheet. Rsense used is 1.8 kΩ as proposed in the evaluation board user manual for 230-240 ...
5 votes
1 answer
210 views

Read in Arduino negative and positive voltages in a wider range

I need to read DC voltages on Arduino that can vary between -15V and 15V. As far as I know, Arduino can only read positive voltage values ​​between 0-5V. I thought of using a voltage divider with a ...
2 votes
3 answers
96 views

How can I measure the output of a voltage booster circuit?

I made this circuit, which was described on-line as a "transformerless Joule Thief." I was able to light four LEDs of varying forward-voltage in series, but I couldn't figure out how to use ...
0 votes
1 answer
402 views

Measuring voltage drop across a 100 ohm resistor from an isolated power supply

I am new to this and i need help with a question I have in a circuit I want to measure the voltage drop across the resistor RS1. The opamp is powered by a 5V supply rail. The 50VDC is coming from the ...
0 votes
0 answers
61 views

Noise in measurement

I'm having a problem when I measure a voltage from a lead battery. I provide my circuit so you can understand better whats happening. For example I measure a 24 V battery, goes to a resistor divider ...
0 votes
1 answer
195 views

Connect probe properly to measure 230 VAC with oscilloscope

I just got this combined multimeter - oscilloscope Hantek 2D72  Link to manual: https://www.circuitspecialists.com/content/476383/HANTEK2D72_Manual.pdf&ved=...
3 votes
1 answer
46 views

Voltage variation in the output of Differential Amplifier

I am working in low side current sensing differential amplifier circuit. VA is connected to ground and resistance R2 is also connected to ground but both the grounds are not same then there is voltage ...
11 votes
4 answers
32k views

How does a non contact voltage tester work?

How does a non contact voltage tester pen detect voltages and/or currents? Are they limited to voltages of a certain range or type (AC or DC)? Here's some experiments I have conducted that lead to ...
0 votes
1 answer
279 views

Dynamic voltage divider

I'm trying to build an ESC (electronic speed controller) for three phase brushless motor. I found some intresting circuits but I am trying to build something very easy to do, with mosfet and pc817 and ...
5 votes
6 answers
610 views

Voltage drop over open circuit

I am still learning the basics of electronics and this confused me: I have a simple LED circuit like this (5V voltage source): The LED has a specified voltage drop of 3V, and is rated for currents of ...
0 votes
3 answers
89 views

Are Arduino inputs equivalent to voltage measurement?

I read somewhere that Arduino input pins basically (more or less) just measure the voltage at their pins with respect to ground (and then, based on that, create an analogue value or a digital HIGH or ...
0 votes
1 answer
305 views

RMS and average value of a DC signal - Which is the correct way to eliminate the inaccuracies due to incorrect measurement setup?

I have a 5V DC signal and there are some ripples on top of the DC signal in the range of 50-100mV (maybe due my measurement inaccuracies or the switching noise coupling from other sources.) In that ...
3 votes
2 answers
167 views

Is this op amp circuit a promising idea to measure 300VAC?

I need to measure 300VAC. I am using the following circuit and it is working good. In the circuit, I am using 2mA/2mA current transformer. More details about this transformer are available here. ...
1 vote
0 answers
57 views

How do Fuel gauge ICs compensate for battery aging?

I came across this Fuel gauge IC recently and although I understand how the SOC is determined, I do not understand how the age compensation constant(the one used to determine the actual SOC) is ...
1 vote
0 answers
38 views

What's the per phase equivalent circuit of induction motor with asymmetric windings?

We know that there's T equivalent circuit and inverse Γ-equivalent circuit for 3 phase induction motor(IM). When the IM is operating under normal situation, the windings are symmetrical, so all 3 ...
0 votes
2 answers
2k views

Op amp buffer output voltage offset

I am building a system which will measure and record the voltage of batteries. There are 8 channels in the system with each channel being capable of measuring 0-35 V. The accuracy we have decided upon ...
0 votes
1 answer
371 views

Battery Cells Voltage Measurement

I'm using LM324 Q-op amp as a differential amplifier for measuring the voltages of 19-cell battery pack in series which happens to be 1.5 volt for each and the differential amplifier gain ratio is 1:1 ...
0 votes
2 answers
67 views

IV curve has non zero current in open circuit condition

I have an IV measurement program running in LabVIEW, where I measure the IV curve of a photovoltaic module using a programmable electronic load from a quick backward sweep (from Voc to Isc.) I have a ...
0 votes
2 answers
225 views

Isolated AC line voltage monitoring circuit

I found this https://www.edn.com/isolated-circuit-monitors-ac-line/ circuit in my quest for a low cost isolated AC line voltage monitor and constructed it. On testing however, I am not getting the ...
1 vote
0 answers
93 views

Check if two voltages (with different grounds) are within 0.5 V of each other

I have designed the following circuit that should be able to detect if two voltages Bus Bar VBAT and VBAT that are referenced to Bus Bar GND and GND, respectively, are within 0.5 V of each other. On ...
1 vote
0 answers
77 views

How to accurately measure average temperature of a heating element?

Problem I'm trying to very accurately measure the heat of a nichrome wire as current is passed through it. My approach thus far has been to monitor current and voltage across the heating element and ...
2 votes
2 answers
326 views

Measuring the minimum voltage square wave

I would like to measure if an 1 kHz square wave signal ±12V 10-80% duty-cycle has a minimum voltage of -11V at Vm. simulate this circuit – Schematic created using CircuitLab So I would like to ...
3 votes
2 answers
168 views

Digital voltmeter reading half the voltage measured with Fluke multimeter

I recently purchased these cheap digital voltmeters from Amazon to display the output of my 2.5 kV HV supply. The HV supply has a dedicated 1/1000 output (0 - 2.5V)for monitoring, which I am trying to ...
0 votes
1 answer
276 views

Connecting multiple voltage sensors with the STM32 Nucleo board

I want to connect multiple voltage sensors to the nucleo board. Lets say 4 voltage sensors of same kind with same address. So, I thought I could connect all the 4 sensors with the nucleo board with ...
2 votes
2 answers
116 views

Voltage limit of differential amplifier?

I need to measure the voltage difference between two high-voltage points (~500 Vdc). I'm thinking of using a differential amplifier with a gain of 1/100. While it behaves as I want it to in the ...
1 vote
1 answer
481 views

Power monitoring difficulties using ACS71020 30A SPI and PSoC 5LP

I'm currently developing a board for my dissertation that should monitor voltage, current and power consumption of a given load. For that purpose I chose to use the Allegro ACS71020. The one I chose ...
2 votes
1 answer
439 views

How to calculate the maximum voltage of square signal from Erms?

How do you calculate the maximum oltage from Erms when you have dc and ac component?
0 votes
1 answer
40 views

How do clamp multimeter sense presences of AC voltage?

If a clamp meter is taken near a AC supply line, it's AC voltage sense LED starts to glow. The same coil that is used for current measurement is used to sense the presence of voltage. As far as I know ...
0 votes
1 answer
70 views

How can I measure a battery's level in percentages using a voltage divider and an ADC?

I want to measure the battery level of 4 AA (R6) batteries using a voltage divider made of 2 resistors which goes into the internal ADC of a PIC16F microcontroller with a 10-bit resolution. Knowing ...
-1 votes
1 answer
69 views

What is the phase difference between phases in 3phase system, if system becomes unbalanced

Is the phase difference between the voltage phase 120 degree in an unbalanced system if not what how can we calculate it? I will try to explain this a litte more clearly. More specifically in this ...
3 votes
3 answers
85 views

Should ADC reference pin also be a kelvin connection?

Reasking this question with a proper schematic: I am doing a ratiometric measurement of a Thermistor. The thermistor is located over 5 metres away from the ADC and all other components. This is going ...

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