# 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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### Difference in noise performance between UK system and US installation

We have a piece of high-gain measurement equipment that we tested extensively in the UK and the found to perform adequately. This is a mains powered device, with the electronics powered through a ...
4 votes
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### 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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### How does this capacitance measurement op-amp circuit work?

I'm studying this scientific paper where a capacitance measurement is done with the circuit shown at page 3. For simplicity I reported it here: A sinusoidal signal is applied at the input through a ...
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3 votes
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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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3 votes
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### 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 ...
2 votes
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### S11108 Circuit Design Logic

This is my first post and also my first dip into electrical engineering, and I wanted to ask if you have any suggestions on the circuit I have designed. As a background, I'm a Computer Science student,...
2 votes
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### Using a DAC to measure system gain

I am using a Wheatstone load gauge through an AD8295 op-amp to a SAMD21 uC ADC. The op-amp uses a resistor to set gain. An analog switch is used to change gain. Since the resistors are not exact (G = ...
2 votes
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### Is it necessary to implement a sensing resistor plus pre-amp with Faraday cage on a PCB if I would like to have the range about 10nA measurement?

I put a 60 kΩ sensing resistor plus low-bias current amplifier with a gain of 500 into an aluminium bag and tied it to AGND for EMI shielding. The second stage is an ADS1256 24-bit ADC. The purpose is ...
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### 50 Hz noise from mains plug even though it isn't connected to a power source

I am developing a front-end for a smart meter and I'm trying to measure the mains by using a power lead with the other end spliced to connect it to the front-end. I firstly powered the setup with a ...
2 votes
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### How to determine LS, CS, RS, and CO of a piezo transducer for simulation?

I have a 24mm piezo transducer with the marking SSE2425TAL from overseas. There are no detailed specs nor graphs to get LS, CS, RS, and CO at various frequencies (but just 25 kHz is fine). I'd like to ...
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### Electrochemical Gas Sensor Potentiostat Circuit

I guess this is more of a review request than a specific question, but I was wondering if anyone has any experience with electrochemical sensors and the required circuits for gaining accurate ...
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### Does creep always occur with load cells, or is there an optimum weight capacity?

I want to make a scale which I will place under a wood stove (downdraft gasifier) to measure the amount of wood that goes into the wood stove. The amount of wood which is being measured will be ...
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### Vacuum tube emission (anode current, transconductance) percentage that is considered GOOD

Russian vacuum tube datasheets almost always specifies anode current like Ia = 100 mA +/-20mA at some conditions. The same with transconductance. But western tube datasheets specifies only one ...
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### How do I measure an 'industry standardised' noise given Vrms ~ oscilloscope settings?

I have an example of a noise source, but the specific device is unimportant to the fundamental aspect of this question. I'm trying to measure it's level with an industry standardised method so that I ...
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### Is the quantization error and random error included in the of-range error for multimeters?

When I am looking at a datasheet for a DMM (Digital Multimeter) to calculate the accuracy of a measurement it specifies two error sources: of-range and of-value (also called of-reading). For example ...
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1 answer
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### Error Analysis due to Voltmeter Constraints

I got a situation: at the moment I am unable to access both channels for Keithley 2182A nanovoltmeter using LabVIEW. However, for some odd reason, while I cannot access the channels at once, LabVIEW ...
2 votes
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303 views

### Cortex-M DWT cycle counter inconsistent measurement

I recently discovered that it's possible to use a free running counter embedded in most Cortex-M4 cores to measure the performance of a chunk of code. I'm trying it on my LPC4370, where I want to ...
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### What is a suitable hysteresis value and averaging period for a residential thermostat?

I've built a microcontroller based thermostat that I am using to control my home HVAC system. The actual programming and physical assembly has been straightforward. I'm using DS18B20 sensors, so I ...
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### 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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### 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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### 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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### Contactless measurement of internal time base

I'm currently trying to measure the internal time base of stopwatch (both mechanical and digital) to ascertain the expected accuracy of the device. I have looked through many articles related to the ...
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### HLW8032 energy meter circuit showing power usage at no load

I am designing an AC energy metering circuit. The circuit has to measure voltage, current, power, power factor and energy used for two channels (from the same source). The HLW8032 transmits 24 bytes ...
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### Making earth pit in swampy area

I recently made an earth pit in a swampy area. I dug the earth up to 5 feet as water was available at 4 feet depth. I poured charcoal and salt in the ratio of 3:1 . After braising the copper plate ...
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### Contact measurement

I have a mechanical assembly that is to be mated to another surface. To ensure that my assembly is correctly mounted before installation, I have a test piece I insert into it. When everything is OK ...
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### How do I measure impedance at high power?

I need to measure the impedance of a passive device at its operating power, about 100-watts, and its operating frequency, from 0.1-MHz to 10-MHz. The venerable "operating impedance bridge" ...
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### How do you "calibrate" (?) a matching network to re-optimize an S11 match based on physical measurements from a VNA?

We made EDA simulations to match an LNA input and had good results on the simulation (including EM simulation!) --- but when we built the board in real life the S11 match went from -30dB to -7dB. Ouch....
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1 vote
1 answer
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### Number of data points needed for INL DNL estimation

In this article where ADC of pico pi is characterized, I found a part that I have never encountered in my study of mixed signals design: I don't understand how we number of data points needed is ...
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### HX711 zero factor

I have three load cells (YZC-1B). These load cells' capacity is 50 kg. I guess I use Bogde's HX711 library. In monitor, the zero factor for the first two load cells is 8,000,000, but for the last load ...
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### dB SPL Calculation is not making sense- values are seemingly too high

I am using an electret with a sensitivity of -38.44 dBV to make sound measurements at a distance of 1m. I decided to add an amplification circuit with a gain of 125. So in the end to convert to SPL, I ...
1 vote
1 answer
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### Better displacement finder? Lasers/Inertial Sensors

I've seen laser rpm measurement devices. But can it be used the find displacement/distance moved for object when attached to it? I know taking rpm of wheel and multiplying by circumference would give ...
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### Measuring average DC of pulsed analog signal

I'm trying to measure average DC level of pulsed analog signal. The pulses have minimum pulse width of 10 us and amplitude of max 5 V. Pulses are somewhat gaussian shape and have very random height ...
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### My first full contact-less power meter doubts

I need to measure power consumption of an industrial machine, it is supplied with 3-phase plus neutral connections, 220V per phase. They said there is a voltage stabilizator device between the power ...
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### Steps for connecting femal-to-female sacrificial adaptor into a male connector in the RF measurement equipment

First of all, I am a newbie to the RF-mm-wave test equipments. I am trying to use this Agilent equipment shown in the image below where I want to connect a 1.85mm (F-to-F) sacrificial connector to the ...
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### Calculating Antenna Directivity Numerically

The equation for peak directivity of an antenna is this (example source) {D = \frac{1 }{ \displaystyle \frac{1 }{4 \pi} \int_{0}^{2\pi} \int_{0}^{\pi} |F(\theta,\phi)|^2 sin(\theta) \, d\theta d\...
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### Measure distance to object with angular precision - invisible for camera

I want to build myself an arduino based follow-focus. There is one mode intended for using a joystick for manual control of focus and zoom. This code already works a treat. Now I want to add a ...
1 vote
1 answer
244 views

### Measuring battery resistance

I am trying to measure the resistance of a AA alkaline battery. The circuit I am using is shown in a photo below. I have also attached the values I obtained. Somehow, the values I am getting ...
1 vote
2 answers
642 views

### Measurement of transformer with a vector network analyser (VNA)

I have a planar air core (no ferrite) transformer in a PCB. I need to characterize the transfer function of this transformer from DC to 500 MHz using a vector network analyser (VNA). My first ...
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### Connecting ADC ground to alive part of a power supply board for measurement

Before start, this is going to be a long question. My apologies in advance! At my company, we are trying to design an automated engineering validation test (Auto EVT) tool for power supply board (...
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### 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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### 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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### 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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### 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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### 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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### 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. ...
1 vote
1 answer
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### Using a scope for an instrumentation and mains earth

When I make a measurement using a scope and observe transducer voltage output on the scope screen, I want to eliminate the noise as much as possible which is due to device and scope coupling or common ...
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### 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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### Converting Uncertainty in dB to Relative Standard Uncertainty

Data sheets often give uncertainty in dB. If uncertainty is specified as a percent, I believe that means it is a relative uncertainty. Assuming the coverage factor is one, the relative standard ...
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### 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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### 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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