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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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103 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 ...
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1answer
91 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 ...
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0answers
95 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 ...
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3answers
99 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 – ...
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2answers
398 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-...
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3answers
890 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 ...
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1answer
148 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 ...
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1answer
479 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 ...
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3answers
555 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 ...
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0answers
103 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 ...
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2answers
54 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 ...
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1answer
78 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
333 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 ...
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2answers
471 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
643 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 ...
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1answer
77 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
121 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 ...
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1answer
392 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 ...
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1answer
673 views

Battery current measurement with shunt resistor

I want to use a shunt resistor to measure the current that flows from and in a battery. The current is set by power supply for charging(positive current) and by electronic load for discharging (...
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1answer
457 views

AD620 doesn't amplify signal between 1-60mv

I want to amplify a differential voltage signal between 1-60mV usign AD620. But I don't understand why it doesn't work. If I remove Rg I must have gain=1, instead I have a gain smaller than 1. I ...
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3answers
82 views

Replacing Multimeters with Megaohmmeters

Standard Digital multimeters can measure up to the ranges of 20 Megaohms. Then why should we use Meggers at all?
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2answers
516 views

How do I measure the error of my ohmmeter

I have to do an Ohmimetro to a college assignment, but I don't know how discover the measure error of my circuit. When we buy a multimeter, the equipment has a measure error calculated by the ...
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0answers
29 views

Practical verification of equations

This question is reffering to MOSFET. If you calculate drain current with a specific formula you can also verify that same value with measurement. But if you calculate partial or overall gain, you ...
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2answers
361 views

Op-amp with constant gain for small signal(mV)

simulate this circuit – Schematic created using CircuitLab I want to measure current using shunt resistor and I want to amplify the voltage over the shunt using an op-amp. The shunt resistor ...
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0answers
37 views

current measurement in series-parallel solar panel array

I have a solar panel array wired in series-parallel. I know the voltages in a series network will be the average voltage, and the current in a parallel network will be the smallest contributing ...
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2answers
128 views

Measuring mains - shifting ground from mains to bridge

The circuit below is a simplified and partial front end schematic of a solution that measures main voltages and takes action if over voltage, under voltage or "wrong voltage" (e.g. user plugged into ...
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0answers
127 views

Why does inside of my sphere appear to be getting darker?

This a fully enclosed sphere containing a web cam, white led and photo resistor in exactly the geometric arrangement shown. The led glows dimly (via fixed dropper resistor). It runs at about 9 mA. ...
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1answer
180 views

Measuring electric current in shield

I have noticed that there is some current (not dangerous levels) in the shield around the power supply in my computer. Would it be safe to measure the current (Amps) going through the shield with a ...
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3answers
430 views

cheap sub uH inductance meter?

Can a cheap RTL-SDR (with suitable software) plus a variable frequency digital output (for noise or square wave generation) be used to construct an inductance meter suitable for measuring values in ...
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4answers
568 views

Measuring noise on DC rails with active probe

I have a Tektronix P6245 active probe (allows only DC input) and wish to use it to see noise on various power supply rails. I've done this already on a +3.3V rail, and can get sufficient DC offset on ...
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2answers
101 views

load cell number and accuracy

I want to measure weight, so I use load cells, As far I know, commonly 4 load cells are used for this purpose, but I can not understand it's real purpose, maybe 2 will be more accurate than 4? Is it ...
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1answer
192 views

Proper way to measure an AC signal with an oscilloscope

Is there a correct way to measure an AC source with an oscilloscope? As shown in the schematic below, I've got a current transducer that is expected to output an AC current of about +/- 1 mA (approx.)...
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1answer
161 views

Contact-less liquid level indicator [closed]

I am developing a Liquid level indicator to be used for my lab breaker. The purpose is to get real time liquid level data on computer for analysis. I have searched for many liquid detectors, but ...
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3answers
3k views

Precision Power Supply / Elektor, December, 1982

Since this PSU was published by Elektor I assume that some of you might heard or read about this project. http://www.retro.co.za/zs1ke/projects/PrecisionPowerSupply/PrecisionPSU-Elektor-Dec-1982.pdf ...
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3answers
816 views

ADC and internal noise

I have a question regarding AD conversion in a microcontroller. Before we go on, I use a dsPIC33EP64GS506 (link on its datasheet), 3.3 V power supply, and 12-bit ...
3
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1answer
852 views

At what test frequency should electrolytic capacitors be measured?

At different frequencies electrolytic capacitors have different capacitance. Suppose it is 50 uF 16V capacitor (type K50-16), then the measurement results are (using russian E7-14 RCL tester): ...
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1answer
101 views

ACS712 cutting out

I'm using an ACS712 based current sensor board (Exact here: http://tinkersphere.com/sensors/1244-hall-effect-current-sensor-breakout-acs712.html) For testing purposes I have connected Vcc and GND ...
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1answer
1k views

Any way to measure distance through water?

I have a barrel of clear liquid which has sediment build up at the bottom of a barrel. Over time I want to measure the build up of this sediment. Nothing can touch the liquid and I can't place ...
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1answer
217 views

\$V_{BE}\$ decreasing with \$V_{CE}\$ at constant \$I_B\$ in a BJT common emitter?

I took measurements on a TIP31 common emitter BJT transistor. The circuit was the one in picture I observed a fact which seems quite unusual. Keeping \$I_B\$ constant, for different values of \$V_{...
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3answers
1k views

Should a capacitor be considered functional if it's capacitance reading is correct?

There are many different ways to test capacitors. Using a capacitance meter, using a DMM and an analog meter. In general, is it safe to assume that a capacitor is considered functional if it's ...
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1answer
125 views

How to estimate displacement error using accelerometer

I am using an MPU6050 and performing a double integration to obtain displacement, and this is to be placed in a vehicle that will be subject to about 2.5g. I cannot test it now, but how is it possible ...
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3answers
1k views

What is “Vref” of ADC in a microcontroller datasheet?

I'm kind of lost in the datasheet of the µC. I'm using an XMC4700 µC. I will connect a voltage divider to the input of the ADC to measure the voltage. I found the equations to calculate the result. ...
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0answers
94 views

Can a capacitor have high series resistance and low Q and why?

I measured with an LRC meter (Agilent 1731A) a capacitor at frequency \$1kHz\$, finding \$C=109.4 n F\$. Then I tried to measure the resistance and quality factor of the capacitor: here is what I got....
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5answers
3k views

Measuring the resistance of a real inductor?

Real inductors can be represented as perfect inductor plus a series resistance \$R_s\$. The impedance of this component is \$Z_{L+R_s}=R_s+j \omega L\$ therefore $$\frac{1}{Z_{L+R_s}}=\frac{1}{R_p}-\...
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1answer
87 views

Measuring current and internal impedance of current source

I am building a current source for an EIT project that I am doing. I have not reached the multiplexer part as I am still having issues with my current source. I am developed the current source as ...
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3answers
652 views

Understanding “dBc” in the context of IM3

Let's say I'm doing a two-tone test to measure intermodulation distortion in an RF power amplifier. I look at my spectrum analyzer1, and I see this: The tops of those main lobes are at -105dB, and ...
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1answer
451 views

When is it necessary to connect all scope probes to GND (instead of just one)?

Oscilloscopes typically have multiple input channels which have a common ground (which also happens to be earth referenced). The problem is that the probes can be connected to ground through a huge ...
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2answers
878 views

Verifying supercapacitor capacity

I have procured some supercaps. No datasheet was provided. The only data I have is what is printed on the caps themselves: "4.0F 5.5V cda®" Since my DMMs don't ...
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0answers
42 views

MEMS or other modern component electroscopes

I was looking for a component-style electroscope. I thought, "Surely there must be some MEMS-based electroscopes capable of 2- or 3-significant-figure potential measurements." But the only thing ...
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2answers
1k views

How to calculate internal generator resistance?

What's the formula for calculating generators internal resistance in a circuit with a load? I am given the load resistance and the voltage sources voltage. What's next? simulate this circuit – ...