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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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1answer
612 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?
3
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3answers
454 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 ...
8
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3answers
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 ...
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2answers
140 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, ...
1
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1answer
65 views

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 ...
1
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1answer
95 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 ...
0
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1answer
86 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 ...
0
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0answers
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 ...
0
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1answer
108 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 ...
4
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4answers
836 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 ...
0
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0answers
193 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 ...
0
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1answer
203 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 ...
0
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1answer
71 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 ...
2
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0answers
87 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 ...
5
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2answers
176 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 ...
1
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0answers
338 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: -...
0
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2answers
177 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 ...
0
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1answer
112 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...
10
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2answers
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 ...
0
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2answers
113 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 ...
1
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0answers
73 views

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 ...
0
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1answer
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 ...
0
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1answer
446 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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3answers
185 views

How to do Non contact USB wiretapping?

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 ...
0
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1answer
468 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 ...
3
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2answers
391 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 ...
0
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2answers
165 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 ...
1
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1answer
56 views

About ideal floated measurement

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}\...
2
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4answers
1k views

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 ...
2
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6answers
2k 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 ...
0
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0answers
161 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 ...
5
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4answers
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 ...
2
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2answers
234 views

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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2answers
91 views

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 ...
2
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1answer
90 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 ...
0
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0answers
94 views

Capacitor reading 1/10th of the rated value

I have a Siemens fridge that is not cooling. All of my fans are running etc.. I have been troubleshooting the compressor, relay and overload which are all fine. I then decided I'd measure the ...
0
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3answers
94 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 – ...
0
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2answers
352 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-...
3
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3answers
818 views

4 Wire Strain Gauge to 2 Wire Conversion/Connection

I have the WK-06-12BT-350 ohm WK125BT Strain gauge from Vishay the Gauge comes equipped with 4 wires ( High endurance lead wires). The following document describes a similar gauge: Strain Gauge is it ...
0
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1answer
143 views

Test an LCD for missing segments without looking at the screen? [closed]

I have a product with an LCD screen that sometimes fails with missing segments. I will test the product for a long time to replicate the failure. I will test many at once. I don't want to sit watching ...
-4
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1answer
422 views

RC oscillator to measure capacitance with a microcontroller [closed]

I want to measure capacitance sensors with a microcontroller. One way to do this is to use comparators and measure charging time. As I cannot (and don't want to) use comparators I thought to build ...
0
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3answers
490 views

Optical odometer

For my device moving above the surface (railway tracks) I need to be measuring the distance traveled. So far I have been using a wheel with IRC (incremental rotary sensor). To simplify it I would like ...
1
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0answers
93 views

Equipment to measure strong constant (in time) and slowly changing electric fields

I would like to measure the electric field in the vicinity of an object of interest. I would like to have decent spatial resolution (i.e. be able to pinpoint a measurement to a point in space within ...
0
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2answers
53 views

How to relate voltage Output to temperature with a Wheastone bridge

I have a circuit like the one below : with R1=10kOhms, R2 = R4 = 20kOhms and R3 is my thermistor (=10kOhms at 25°C). I want to read the voltage V-Out on an arduino so that I can measure a ...
0
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1answer
77 views

Unknown hardware filter/amplifier in setup

I found the following picture on the internet. To be honest, it was the first time I saw such a (filter/amplifier?) plugged in an oscilloscope. Anyone knows which device it is? Thanks in advance ;)
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2answers
276 views

Confusion with a measurement method suggested for an opamp input impedance

Before asking my question, I want to show the probe and scope model I use in the simulation: In the above schematics the section inside the rectangle represents a scope probe set for DC coupling at ...
2
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2answers
416 views

Measuring the power output of a hand-crank generator

I am working on a project which aims to compare the energy generated from a hand-crank, DC generator, to that of solar panels. The hand crank generator will not actually be powering anything, but we ...
2
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1answer
601 views

Water conductivity measurements/ESP8266 - getting strange results

Hope this is the correct forum and thanks in advance for reading this. Summary: I'm working on EC (electric conductivity) measurements using a capacitor and the pins of an ESP8266 microprocessor to ...
-2
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1answer
73 views

Is it possible to save data from a network analyzer?

Im using N9917A Network Analyzer for measuring s-parameter values. I have connected the VNA to PC via Ethernet cable, where I can view the resulting plots of s-parameter values. If i get 15 plots of s-...
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1answer
111 views

Rigol Arbitrary Waveform Generator DG1022Z and Square Signal Sample Rate

I have generated simple arbitrary function which represent UART message, but I'm having trouble when it comes to decoding it on oscilloscope. The reason for that is because my 0 and 1 at frequency ...