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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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Why do long cables measured with a VNA show a “drop” in their attenuation curve?

I'm measuring the attenuation of several cables with a VNA (Keysight N5234A). When I measure the attenuation of long cables (10 m, 30 m, 40 m or 50 m) I realize that a "drop" appears at 500MHz (see ...
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Measuring integrated current

I want to measure the amount of light striking a photodiode in a specific time window (about 1ms). In this window, we get \$10^6-10^7\$ photons, which get converted into electrons with about 80% ...
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63 views

How can I make my measurements of full-wave rectified AC using an A/D match a Fluke meter on its DC range?

I am trying to measure the DC voltage of a full-wave rectified 60Hz AC signal using an A/D and have it match what a Fluke meter reads on its DC scale. My current approach is to take as many (16 bit) ...
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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 ...
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106 views

How to properly store big values in parallel SRAM

For a project I need to determine the frequency and phase-shift of up to 16 channels. The frequency range is 0 to 3 kHz and the signalform is square. My first idea was to use the following circuit ...
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782 views

What is the accuracy of a thermocouple after calibration?

I'd like to use a thermocouple to create a general-purpose temperature probe. However, the accuracy is quite a bit lower than I want. Almost every source I look at (example) lists the accuracy of a ...
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137 views

Precision Tracking filter required

I don't mind if it's a band-pass or low pass filter (although I think low-pass will give a better result). Input operating frequency range is 100Hz to 1kHz. Input amplitude will be about 1Vp-p and ...
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87 views

Wrong measurement of DSO-5200A?

I'm using a DSO-5200A from Voltcraft and noticed the voltage measurement represented incorrectly (it is doubled). Any ideas how to reset this? Channel 1 (green) measures a (noisy) 5V and has a Vmean ...
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62 views

MEMS Microphone noise floor power level & audio noise spikes measurement

I have a circuit with a MEMS microphone and would like to be able to measure the audio noise spike contents and check the noise floor power level in the audio circuit. My intention is to connect the ...
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104 views

Power consumption measurement on the bench

I've been using the Atmel Power Debugger to sort out power consumption issues on some µController based circuits... and have been pretty pleased. Unfortunately, it's limited to a maximum of 5.5 volts ...
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39 views

Measuring resistance of switched load

I am in the process of designing a custom vaporizer. So the main coil with a resistance ranging from 0.2 Ω to 2 Ω is switched using a MOSFET shown in the circuit diagram below. ...
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149 views

What's inside a reed switch that cannot be tested with a multimeter?

I'm shopping for reed contacts that are rated for 230V AC, because I don't want to use an always-on power supply just for a relay and a reed switch. This is surprisingly difficult, but I found this ...
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183 views

Measure input capacitance of I/O pin

I'm looking for a simple laboratory procedure (and required equipment) to measure the input capacitance of each IC I/O pin. Thanks in advance.
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78 views

How to figure the wiring of a 4 cable pc fan without frying it?

I have a 2 spare PC Fans which come with a four cable wiring and I would like to reuse them as ordinary fans (running at full speed all the time) outside a PC box, powered by a 12v source. ...
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87 views

Am I right about measuring current, and power

I have a meter that can measure: current, active power, reactive power and complex power. simulate this circuit – Schematic created using CircuitLab So, when I measure the four things: current,...
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387 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: -...
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78 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 ...
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104 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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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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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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137 views

How to extract complex permittivity from a CV measurement?

I can choose from the following measurements: Z, theta (impedance and phase angle) R + jX (resistance and reactance) Cp-Gp (parallel capacitance and conductance) Cs-Rs (series capacitance and ...
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205 views

Do “True RMS” meters really do RMS if the input is a high frequency signal?

I'd like to measure the average of a signal which is mostly zero (less than a few nanovolts as best as I can tell) but may have occasional nonzero "blips" of maybe 20-100 nanoseconds (maybe 1V tall). ...
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375 views

Li-SoCl2 battery state of charge

I'm developing a data logger powered by Li-SoCl2 (http://www.100y.com.tw/pdf_file/02-SAFT-LS33600.pdf) battery and I have no idea on how to overcome the problem of estimating the residual charge of ...
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314 views

Need help with generating a bi-phasic current

I'm trying to generate a symmetric biphasic current pulse using a Grass S88 Stimulator. Here's a diagram: SG is a signal generator with two outputs, S1 and S2, which are generating a periodic pulse ...
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22 views

Correcting DC offset in op-amp based controlled current source

In an attempt to develop an automated potentiometer measuring device I have implemented the following op-amp based voltage controlled current source, controlled by the output of a DAC. The voltage ...
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Hspice : find max of measurement result in Hspice

i need to calculate efficiency of a circuit for diffrent parameters and then, find MAX of these efficiencies in Hspice.( also related parameters that refers to it) i ran i .DATA transient simulation,...
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62 views

Photodiode to detect light

For a university purpose I am preparing a project, actually I am thinking of using a photodiode in reverse bias in order to measure intensity of light. I divided this project in some phases: 1) ...
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57 views

How to eliminate oscilloscope channel DC bias

When I set channel 1 as DC coupling, there is always -5.6v bias, even no cable is connected. Can someone tell me how can I eliminate this bias? Thank you
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49 views

Amplifying pulse signals causing pulse lengthening problems

I am currently trying to design a circuit that would sense a voltage change at its input, convert that change into rapid "on"/"off" change at output and amplify same switching voltage to high current (...
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30 views

Can I use a RF and/or Time-domain reflectometer to find 'wet contact'?

Friends of mine have a circuit where the RCD trips but only after prolonged rain. There are a number of garden and security lights on that circuit so I very much suspect there is a junction box where ...
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84 views

Darlington Transistor TIP142 same type but different values

I have a bunch of Darlington NPN Transistors TIP142 that are removed from two separate identical boards. The 1st one have the TO−218 CASE (left side of the image) and the 2nd the TO−247 CASE (right ...
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61 views

Measuring current in the case of bridge amplifier at several MHz

Is there a way (or some chip) to measure current at about 5 MHz when the bridge amplifier is used? The output is a sine with amplitude 15 V. I need to measure accurately both amplitude and phase (the ...
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32 views

Effect of AC output impedance on a ratiometric measurement

I was planning to make a measurement with a ratiometric IC, so I will sense both the Vcc and the Vout from the chip as shown below. For cleaning up the noise and stability I also want to add a 5V ...
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81 views

Impedance magnitude and phase error - Mathematical formula

Today I read a paper on which there are the terms magnitude error and phase error relative to a comparison between measurements performed with a biosensor and with a benchtop electrochemical impedance ...
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51 views

What is the use of making measurements using both forward and reverse currents? (Kelvin bridge)

For measuring low resistances using the Kelvin double bridge arrangement it was mentioned in our electrical measurement lab class that we should use both a forward current and a reverse current (i.e. ...
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42 views

Measuring small strain with strain gauge, how nullify errors?

I have a similar circuit like https://www.egr.msu.edu/classes/ece480/capstone/spring15/group05/uploads/4/7/5/1/47515639/ece_480_app_note_justin_bauer.pdf 2. page bottom Wheatstone bridge: 2x 350 ohm ...
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84 views

How to measure remaining lithium battery charge accurately (destructively)?

I want to measure the remaining charge in batteries and my requirements may be somewhat unusual. I do not need to preserve the charge left in the battery and it doesn't have to be quick. All I want is ...
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32 views

Techniques for probing circuits that would normaly be covered by a heatsink

I have a circuit board I have to probe and measure to first debug and then later on verify performance. The circuit board contains a power amplifier that requires a heatsink in order to keep the ...
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29 views

Can I use a scope probe to connect a signal generator to a generic circuit?

It's an exam question stated as in the title. I don't know how to analize the problem. As long as it's a BNC to BNC coaxial cable anything goes I think, but I don't know for attenuating probe or ...
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53 views

HF current measurement

I have an assignment, where i'm supposed to (sort of accurately) measure the current drawn by a SIM-card, in the different phases it can operate in. The current is by no means DC, as the SIM-card ...
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314 views

How to connect bathroom scale (arduino+hx711+spark load connector)

Im a new user in the electronic world. I tried to hack my bathroom weight scale but no success. There is a great tutorial which I followed: https://www.youtube.com/watch?v=iywsJB-T-mU my parts: ...
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64 views

Measurement setup for power line spectrum

I've come across a setup for measuring AC power line spectrum. Here is the spectrum graph which shows 60Hz and harmonics in a power line voltage: And below is the setup and wiring for this ...
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227 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 ...
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194 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 ...
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96 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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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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96 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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47 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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58 views

Capacitor tolerance at high frequencies

I was measuring a 10pF 0603 +-5% (Johanson 251R14S100JV4S) using a network analyzer at 319.5MHz. The cap came in their high q/low ESR ceramic kit. It measured about 10.7pF. But after measuring a few ...
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683 views

Making a Tachometer using LED and Laser?

I am making a tachometer to measure speed of a wheel using a LED and Laser. The phenomena is that when Ray of Laser is shown on LED , 0.5 V are produced. I will connect a Schmitt trigger (made using ...