# 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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### Measuring noise with an oscilloscope

What is the proper procedure to measure RMS noise with an oscilloscope? I have 2 standard resistors, 1k and 100k and a 1.5GHz BW, 5GSa/s Keysight DSO. I have a probe which offers 1:1 (1MOhm//100pF) ...
117 views

### What's the difference between measurement resolution and digits per second in time measuring devices

In time/frequency counters/analyzers in technical specifications you can almost always find resolution and digits per second values next to each other. What is the difference?
94 views

### How to measure weight at end of arm

I have a setup where I need to measure the weight at the end of an arm. The arm is clamped between two pieces of aluminum at one end. The Sensor S is mounted a short distance (5cm?) from the aluminum ...
243 views

### ADC MCP3421 sample rate problem

I am writing a driver for mcp3421 ADC IC and I have a problem when I measure in 12-bit accuracy. That is 240 samples per second. In the datasheet the min and max values are 176 SPS and 328 SPS. So I ...
553 views

### Ac voltage measurement

Hi! I got a simple problem. My objective is to measure voltage and power factor of a 16V AC through a differential ADC (ADS1115) that measures voltage difference between 2 channels. I only managed ...
125 views

### How to measure Oscilloscope's self random jitter

I want to measure how much noise is a certain oscilloscope responsible for. Up until now we (my team) have used the approach of inserting a square wave and measuring the random jitter RMS. This method ...
43 views

### Measuring electro-hydraulic drive's inertia

I have an electro-hydraulic drive – a hydraulic motor with coupled to it a synchronous generator. Also there is an encoder installed on the shaft of the generator. By using my DAQ unit I will measure ...
2k views

### How to measure RMS value of voltage using CRO?

I want to measure the RMS value of voltage of half wave and full wave rectified sinusoidal wave using CRO itself. How do I go about it?
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### Calculation of active power and apparent power through sampling

I'm currently working on a power meter device based on simultaneous sampling of current and voltage values, I intend to use this system to measure the active, reactive and apparent power on a non-...
108 views

### How can I reduce an oscilloscope's bandwidth to that of an Arduino's ADC?

The typical sample rate of the Arduino Uno's ADC is ~10KSa/s. Yes it can be overclocked, but lets just consider the normal situation. I'd like to 'simulate' the levels of a white noise signal that ...
162 views

### Improved Differential Amplifier

I made this circuit as shown below: simulate this circuit – Schematic created using CircuitLab After those improvements with current mirror and constant current source were considered, this is ...
910 views

### How do I measure internal resistence of voltmeter without ammeter?

I know how to do it with ammeter, but how can I find internal resistence without ammeter?
588 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 ...
2k views

### Measuring resistance of a capacitor - unexpected results

I'm trying to measure the impedance ($R_x$) of C1 in the RC circuit shown below, but I'm getting some results I can't explain. simulate this circuit – Schematic created using CircuitLab ...
227 views

### Which ammeter to pick for best accuracy and why?

This is merely a theoretical question. If we want to achieve the best accuracy possible while measuring electrical current and we have two digital ammeters available from two different manufacturers, ...
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### How to measure capacitance of soil without being affected by resistance?

I want to make a capacitive soil moisture detector. Capacitance of soil increases with increasing moisture content. Resistance of soil decreases with increasing moisture content. The soil capacitance ...
103 views

### Detect if bud earphones are in ear

I have bud earphones, through which I am listening to music. Air pressure in my ear (after inserting the earphones) is presumably slightly higher than the pressure of the surrounding air outside of my ...
103 views

### acceleration sensor gives wrong values

I try to measure distances with the 3 axis accelerometer that is part of the lsm9ds1. therefore i measure the acceleration in x-axis and y-axis every 5ms and double integrate it over the time. I can ...
39 views

### I need to measure liquid temperature down to -80C [duplicate]

Building a device that will sit inside a liquid that will be a max of -80C and trying to figure out what my options are for measuring the temperature. I was thinking a thermocouple but not sure if ...
124 views

### A question about differential measurement system

Below represents a differential measurement system for a data-acquisition: As far as I understood, in a differential measurement system neither the outputs of the signals nor the inputs to the ...
1k views

### Detect and measure fog outdoors

Currently working on a project requiring me to detect fog, and measure the amount of fog. It doesn't have to be accurate but it has to give a sense of how foggy it is. The device (probably Raspberry ...
248 views

### Poor man's capacitance meter with range control

I'm interested in making a capacitance meter with on-hand parts. Rather than connecting a bare microcontroller I'm inclined on using my Arduino Mega, since it has a built-in power supply and USB ...
246 views

### Why are high-sampling-rate data acquisition boards so expensive? [closed]

An example would be the NI USB-6366. My guess is that it's primarily due to the analog-to-digital converter (ADC) since it should be the component responsible for the high rate conversion, even ...
77 views

### Measuring Low Magnetic fields

Im working on a project where I want to measure low magnetic fields in a wire. The range I want to measure is 0.1 - 10 mG or 0.01 - 1 µT in low frequencies (DC - 500Hz) (This range (0.1 - 10 mG) can ...
92 views

### How might the Lecroy HVFO High Voltage Fiber Optically Isolated Probes Work Internally?

I've been looking into these fiber isolated probes that Lecroy makes (http://teledynelecroy.com/probes/probeseries.aspx?mseries=537), and I'm curious how they're sending the signal over the optical ...
186 views

### Why do electrolytics have a different charge and discharge rate for the same current

I am measuring the charge and discharge rate of a HV electrolytic capacitor (actually three 560uF, 250V capacitors in series) to calculate the capacitance. Note: The capacitors are hand picked for an ...
424 views

### Measure output AC voltage and current from a DC/AC inverter

As the title, I'm trying to measure and display 230VAC voltage and current from a DC/AC inverter on an oscilloscope. I don't know if I can proceed to measure them directly with these equipment: -...
254 views

### How to output a voltage proportional to the speed of a DC motor?

Take a DC motor, as the one in the picture below: I need some kind of analogic signal (preferably proportional to the speed of the motor) that can be used in a control loop. What are two simple ways ...
170 views

### Calculate consumed power/energy in discrete metering

Suppose I measure power consumption after each 1sec interval, and it is assumed that in between the interval, the power consumption of is same as of previously (n-1...
2k views

### Audible difference between “audio grade” capacitors in the same range?

The following is a list of prices for some capacitors sold by Mundorf, a massively audiophile-approved component company. Each capacitor is within the same product range ("EVO"), and apart from some ...
121 views

### Total resistance in series is less than individual resistance?

I have no idea what is going on right now. I have a microwave oven transformer with 3 coils: A primary coil, a secondary coil and a middle (thick) coil. There wasn't any problem at all measuring the ...
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### Why do we need voltage stabilizion in bridge measuring system with ratiometric connection?

i found in many weight scale reference designs that they use either low noise linear regulator or voltage reference for voltage stabilization. Why do we use them if ratiometric design cancel the ...
61 views

### Measuring generated power (kW) in a power plant and storing/logging values

Given an electric power plant (hydro energy) that currently has just an analog indicator for how much power (kilowatts) is generated, which components would be needed to measure the generated power ...
626 views

### measurement of differential signals using multimeter

Though differential signals are measured through oscilloscope or differential probe, i tried measuring the signals through a multimeter out of curiosity and my observation was that when a voltage was ...
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I am relatively new to electronics but came up with this project, not for nefarious purposes but simply as a cool project. Simply put I want to try and read the data traveling through a USB cable with ...
515 views

### Solid angle measurement conditions for radiant intensity specification in IR-LED's data-sheets

For some IR-LED's their data-sheets state Radiant Intensity and the conditions under which that number was obtained, indicating also which solid angle was used for the measurement. For example, this ...
398 views

### Is there some kind of official standard for signal measurements?

Judging from this question, it seems that different people/sources have different definitions for measurements like amplitude. I personally encountered people disagreeing on the definition of the ...
205 views

### Biased single-source relaxation oscillator not starting

Vcc is 5 V , first op-amp LM358 provides 2.5 V ground for easiest possible relaxation oscillator build with MCP661 (2.5/5.5 V supply, 60 MHz operational range). I wanted to use it to measure values of ...
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In the book "Grounds for Grounding", p. 573, it give a figure: And it states： In a perfectly balanced circuit (i.e., $Z_{H} = Z_{L}$ and $Z_{HG} > = Z_{LG}$), where $Z_{HG}$, and \\$Z_{LG}\...
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### Measuring tension force on rope

Suppose I want wo measure how strong someone (or somthing) pulls on a rope, i.e. I want to measure the tension (=dragging) force on the rope. The pulling would come from only one direction. I assume a ...
3k views

### Ways of estimating phase shift

I have a system that's sampling two 50Hz sine waves at 1kHz. What's the best way to estimate the phase shift between the two? The measurements are somewhat noisy and the sampling period is not very ...
216 views

### Shunt measurement with differential ADC

For a hobby project that I am doing, I would like to measure the voltage across a shunt resistor with a differential ADC. I am thinking to use the ADS1292 of TI. However, I have the following ...
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 ...
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### How to map 10-bit ADC value to a range with restrictions

I need to map a 10-bit ADC i.e. [0-1023] to a range [1-100]. The mapping formula itself is the direct "y=(x-a)/(b-a)*(d-c)+c" to map x in [a-b] to y in [c-d]. Input x is calculated as the average of ...
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### Wind turbine protection comparator circuit

I am trying to design a protection circuit for wind turbine. It suppose to stop turbine rotating when wind speed is to big. I came up with this circuit. simulate this circuit – Schematic ...
93 views

### Current measurment at a high potential

I have a circuit at a high potential compared to ground, up to 30kV, in which I have to measure a current of like 2A. Because the whole circuit is at 30kV I could just measure it with a normal ...
105 views

### Bus voltage measurement in a compact way

I need to measure bus voltage and guarantee my ADC is protected in a compact way. I came up with the following measurement circuit a long time ago in another design. simulate this circuit – ...
456 views

### Are 3 single phases equivalent to a single 3 phase system?

I am not an electrical engineer (I did work as an automation technologist a long time ago, but please forgive me my electricity is very rusty). I've been given some data that was measured from a 3-...