# Questions tagged [measurement]

Measurement is the assignment of numbers to objects or events. All measurements consist of three parts: magnitude, dimensions (units) and uncertainty.

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### What's the most economical way to digitally measure 240V mains voltage, current and power factor?

I'm looking to capture and analyse measurements of the mains energy that I use per circuit. I've found a few consumer products that offer powerpoint energy monitoring such as the Kill-A-Watt, but PC ...
4k views

### Help learning from a mistake connecting an oscilloscope

I have built this circuit to dim a lamp with a PWM signal. It had an issue where the MOSFET was getting really hot. So I wanted to know what was happening on the gate of the MOSFET. I turned the PWM ...
43k views

### How do I measure differential signals (like RS-485 or DMX) on an oscilloscope?

I've encountered differential signals in a few places, such as a differential output audio amplifier and now in a project working with DMX which is similar to RS-485. (Here's a similar question about ...
6k views

### Level of a water tank with a microcontroller

How do i measure the level of a water tank with a microcontroller?
3k views

### Measuring ferrite core parameters

I have large amounts of inductors and transformers from power supplies or other undocumented sources. They are of course completely unmarked and I have no idea what kind of ferrite material they are ...
2k views

### How does 3-wire RTD or resistance measurement works in bridge of wheatstone?

I cannot understand how 3-wire measurement will improve the resistance measurement. They say that IF lead resistance $R_L$ is the same, it will compensate. How can this happen? If bridge is ...
3k views

### Measuring frequency of a signal above 5V with a microcontroller

I want to measure the frequency (up to 300 Hz) of a rectangle signal, that varies between 0V and Vtop, where Vtop is anything between 5V and 15V. Because I cannot apply more than 5V to the ...
6k views

### Water level detection, where water is somewhat polluted and has significant dissolved salts

Found this excellent QnA here which provides several options for measuring or detection water-level. For my case, it is enough to differentiate 4 levels of water (very low, low, middle, full), of the ...
9k views

### Precise Resistance Measurement Techniques

This question is inspired by some basic questions on resistors I've read here lately. What's the most accurate/precise technique for measuring the value of a resistor you can think of? What level of ...
10k views

### How does autoranging work in a multimeter? What is the circuit?

I was curious how this is done. It seems you would have to vary the voltage and current to measure resistance from 1ohm to 10Mohm.
3k views

### How to measure the quality of a USB charging cable?

I have a set of USB cables (data and charge) and I noticed that, for a given charger, the charge time differs by cable. What would be a good way to measure the charging fitness of a USB cable? ...
3k views

### How to measure power consumed by mains device

I would like to measure the power consumed by a mains device. I have heard that it's not as trivial as simply measuring the average current, as the device may be resistive, capacitive or inductive, ...
11k views

### Detecting dry-running of water pump

What are some reasonably reliable ways of detecting that a water pump (electrical motor based) is "dry running", i.e. no water is passing through the pump either because there is no water available at ...
152 views

### Measuring Inductance

I have been looking the number of methods to measure inductance of a coil if you don't have an LCR meter available, and I have had some difficulty. I designed and built a coil and I would like to ...
2k views

### What is the noise level as read on my oscilloscope?

The above is what I'm seeing on my oscilloscope. It's zener diode noise. Scope's set for 0.5V/div vertically, and 1ms/div horizontally. The oscilloscope has a 20MHz bandwidth, but the noise doesn't ...
167 views

### Current measurement maximum time

On my multimeter I have two current measurement connection. One for the mA and one for the A. On the ampere one there's a time limitation but not on the mA one. Also they mention in the manual a kind ...
1k views

I'm writing an embedded app for ATtiny88 - one of its task is to measure voltages of serial connected two 12 V car batteries. The microcontroller is powered from around 4.5-5 V (LM317), measured ...
239 views

### How to measure supply currents ranging from 1μA to 10mA?

I’m building a battery powered data logger with a microcontroller and several sensors. I’d like to measure the supply current of individual parts with idle currents in the μA range and peak currents ...
2k views

### How does one measure the power factor?

How does one measure the power factor? $$\text{power factor}\equiv\frac{\text{power}}{|V||I|}=\frac{R}{\sqrt{R^2+(1/\omega^2C^2)}}$$ for an RC circuit driven with $V(t)=V_0\cos{(\omega t)}$.
396 views

### Measuring an AC-voltage at the ouput of a full bridge rectifier

I've a full bridge rectifier and I put the following function into it: $$5\sin(100\pi t)\tag1$$ So, at the output I get: $$\left|(5-2V_d)\sin(100\pi t)\right|\tag2$$ Where $V_d$ is the voltage ...
516 views

### Measure small capacitance value

I need to measure C value continuously over time, and save the value to some text file (csv for example). Note that C changes over time, since the system is dynamic. C are small, varies between 50 to ...
5k views

### Soil moisture measurement

Background To kick-start my longstanding ambition of getting back into electronics, I decided to try and make a device that measures the soil moisture of potted plants to determine whether they need ...
16k views

### Sending data using 4 pin 3.5mm jack into smartphone

I have been looking around for some time and haven't found helpful information on how this is done. I am working on a project that intends to send data through the headphone jack to be processed by a ...
76k views

### Physically determine unknown wire's gauge

Is there any way to easily and accurately determine the gauge of stranded wire by measuring it? I know you can pretty easily determine the gauge of solid-core wire with just a pair of calipers by ...
47k views

### Can't get a precise reading with PT100 temperature sensor

I am trying to get more precise temperature value from PT100 ( 2 wire ) sensor with Arduino. Here's how my circuit looks like : When the sensor is about 20 °C I get a value on A5 pin that is 432 and ...
2k views

### What kind of oscilloscopes are qualified for measuring USB 3 Super Speed Signals?

I understand that they probably will be very expensive. But I have little idea of what kind would qualify. How much bandwidth? At what sampling rate? Any other parameters?
18k views

### Measuring 0 - 1MHz ( 0.25Hz resolution) Squarewave using an MCU

I need to measure the frequency of square-wave that can vary between 0 and 1MHz, and has a resolution of 0.25Hz. I havent decided on which controller yet but It will most likely be one of the 20pin ...
5k views

### Arduino piezo vibration measurement circuit

I'm looking for a very simple measurement circuit to measure vibrations with a piezo elment and an arduino device. I want to read positive and negative values. I have this sensor: http://www....
2k views

### How can I measure gate capacitance?

Is there an effective way to directly measure the gate capacitance of a power MOSFET, like say the IRF530N? The way my circuit is behaving would indicate that the effective gate capacitance is ...
12k views

### Digital bathroom scale circuit - how it works?

I'd like to understand how the digital bathroom scales work. I was able to gather that there are four three-wire load cells connected into the Wheatstone bridge as suggested below. The load cells have ...
1k views

### Will this approach accurately measure capacitance and infer spacing?

I am interested in any feedback or caveats regarding the following capacitance measurement method before I begin setting it up. For an experiment, I have come across the need to measure and track the ...
4k views

### Predicting thermal equilibrium: what's wrong with my time constant?

I understand that this is arguably a peripheral electronics problem, but it seemed to fit here better than in physics. I've been doing some power electronics design work with large IGBTs mounted on ...
1k views

### How to measure three resistors in a triangle

I have three unknown resistors arranged in a triangle (a delta) and need to determine one of them, which is on the order of 100x larger than the other two, in a measurement circuit. I'm wondering if ...
1k views

### Schrödinger and electrical measurement issue

During the 19's, Schrödinger state that it is impossible to make a measurement without disturbing a system. To illustrate his statement, he made the famous experiment of the cat and the box. Poor cat ...
6k views

### Measuring real and apparent power

I hope my question is in accordance with the rules of the site. I'm doing a power meter using a voltage transformer, a current transformer and an arduino, besides the components to create the ...
911 views

### How to detect low battery of a lead-acid battery?

I've heard that discharging a lead-acid battery to 0% is bad and wears it out. I have a 10Ah 12v lead-acid battery, is there a circuit to tell me when the battery is low?
1k views

### Measuring very small changes in resistor network using current source

I am trying measure a very small change in resistance (approximately .400 Ohms), due to the the effects of connecting a large resistance in parallel with a network of smaller resistors essentially ...
58k views

### Why do measurements displayed in multimeter inconsistently vary by factors of 1000 depending on range?

For my science fair project, I am measuring the resistance of a 100 foot piece of 32 gauge Nichrome wire. Using a Innova 3300 digital multimeter, I get the following results for each resistance range ...
3k views

### How to measure Li-Po battery leakage?

I'm working on a low-low power system, which is powered by a little solar panel and a Li-Po (Lithium-ion Polymer) battery, which can be $20$ or $50\:\mathrm{ mAh}$. The capacity by now is not ...
5k views

### Does this loadcell's creep mean that I can not let a constant load on the loadcell?

I want to build a connected scale that I can set coffee powder (for example) on it and check over the internet how much of coffee I still have without going to see it. Usually all loadcells have a ...
2k views

### Using Logic-Analyzer to reverse-engineer ISM-band ASK/OOK encoding, possible?

Is it possible to use a Logic Analyzer (such as this one), to determine the waveform s.t. on the DATA out pin of an ISM-band ASK/OOK (315/433.92MHz) RF module, in turn to decode it's encoding scheme. ...
5k views

### How to measure capacitance without LC meter?

I would like to use capacitors salvaged from old electronics, but I currently don't have a LC meter. What would be some really simple circuits, that would convert capacitance to something I can ...
807 views

### The best way to get rid off common mode noise for remote measurement

I measure DC pseudo-differentially over 1-2 m wires. In order to avoid any voltage drop in wires the built in ADC input buffers are used, thus there almost no current flow. I expect the wires to ...
4k views

### 3 Wire Digital Scale Strain Gauge Weight Sensor

How do I connect/use a 3 Wire Digital Scale Strain Gauge Weight Sensor? I took it from an old weight meant for people. :) The wires are red, black and white. I found this, http://www.nerdkits.com/...
664 views

### Measuring noisy signals: Does wrapping the test lead through a ferrite reduce common-mode noise?

Let's assume we have a test set-up involving an oscilloscope and a unit we are testing. we measure the voltage between two points using a standard scope lead and see significant noise, I now take out ...
1k views

### Battery Voltage While Charging

I'm experimenting with a linear-mode fast-charge circuit for NiMH batteries. I was surprised to find that the voltage measured across the battery terminals while fast-charging is higher than the ...
3k views

### How to measure output of the ultrasonic transducer?

I have found a test circuit for the ultrasonic transducer. How do I measure the output distance sensed by the ultrasonic transducer using my Arduino Uno R3? Please help. I have attached the test ...
196 views

### Abstract Datasheet Dimension Notation

I am attempting to create a footprint for a Surface Mount Component and I am using the manufacturer's datasheet for reference. They include PCB dimensions but the notation used is a bit confusing. It ...