Questions tagged [adc]

An ADC is an Analog to Digital Converter. This device converts analog signals into digital form. It is mainly used by the digital circuitry to take analog measurements.

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57
votes
6answers
13k views

Why are digital oscilloscopes still so expensive?

I'm a beginner in hobby electronics and I am wondering why digital oscilloscopes are still so expensive? In times of cheap GHz CPUs, USB 3, ADSL modems, DVB-S receivers, blu-ray players which all of ...
47
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7answers
42k views

How do I measure a negative voltage with a ADC?

I am working with a PIC micro-controller with inbuilt 10bit ADC and want to measure a voltage in the range of -1 to -3Volts. I thought of using an op-amp in the inverting mode to make voltage positive ...
28
votes
7answers
7k views

Why do ADCs use 10 bit rather than 8 or 16?

Why is it that most ADCs, like the ones on the Arduino, give 10 bit resolution rather than 8 or 16 bit? It just seems wierd that they don't match standard data sizes, particularly on integrated ones.
27
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3answers
33k views

How to Convert 0 to 10V analog signal to 0 to 2.5V for ADC input?

I have an analog signal which ranges between 0V and 10V. I want to linearly scale it down to 0 to 2.5V for my ADC. I'm concerned that using a resistive voltage divider will affect signal quality. ...
22
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2answers
18k views

What is the difference between an injected and regular STM32 ADC channel?

The STM32F1's reference manual describes "regular" and "injected" ADC channels but is not clear on the difference. What is the difference between the two types and when might you use one or the other?
20
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5answers
11k views

Circuit for measuring high voltage DC voltage (up to 1000V)

I am a final year E&E student and I am trying to built a power meter that must be able to measure quite high DC voltages, up to 1000 V DC. I am measuring with a simple 12-bit ADC that has an ...
20
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2answers
11k views

What is the meaning of “half bit” in this context?

In RS-232 specification, the stop bits can be 1, 1.5 or 2 stop bits...I wonder how it's possible to have half a bit? Also some ADC math uses 0.5bit precision in the IC specifications/datasheet. Can ...
20
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6answers
38k views

What is a differential ADC?

How does a differential analog to digital converter differ from a regular ADC?
19
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1answer
6k views

AVR 1.1V Internal ADC Reference Over-Voltage

If I use the internal 1.1V reference for the ADC, and my Analog input exceeds 1.1V, lets say 2.5V, is that harmful to my microcontroller? Or will ADC value simply clip (to 0x3FF) at 1.1V? For ...
18
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4answers
4k views

Effective number of bits of 14-bit ADC

I have a 14-bit ADC. However, looking at the datasheet (see table 2 on page 5), the effective number of bits (ENOB) is always less than 12 bits. Why is my the DAC claiming to be a 14-bit ADC when it ...
17
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6answers
30k views

How to read high voltages on microcontroller?

I want to read high voltages, like ~50V, using a microcontroller. I plan to put this as an input into the microcontroller's A/D line. But of course, you shouldn't have voltage that high on the input ...
17
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9answers
3k views

Reading a huge number of analog sensors in real time

I'm trying to build a MIDI-like controller that has a neck like a guitar. On that neck, there is a huge matrix of pressure sensors. The controller will emulate 3 strings. The way this works is: ...
16
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2answers
1k views

4-bit bus address selection via analog input pin: Monte Carlo simulation shows overlapping address values

I designed a small sensor PCB for my master thesis with an ATtiny44 microcontroller. I need about 200 of these boards for my application and 16 are always locally connected to controller board. The ...
16
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2answers
3k views

Mixed signal PCB layout for PSoC

I am developing a PCB for an analogue sensing application. It uses the internal ADC on a PSoC3. As usual, the application is very space constrained (11mm x 21mm), so I have had to make some ...
15
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4answers
3k views

Receive several fm-radio stations at the same time (~10-20 MHz wide summary at 90MHz radiofrequency)

What is a cheap way to receive and record on PC several (tens) of fm-radios (public, e.g. news, music, etc)? Such radios uses frequencies like 90.4 MHz or 102.7 MHz, sends a stereo (sometimes with ...
14
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4answers
12k views

What is a one-bit ADC good for?

I have recently heard of the concept of a one-bit ADC, and have seen it implemented in the context of a sort of digital-to-analog converter (oddly enough), and I'm wondering, what is the point? Why ...
14
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3answers
5k views

What's the highest precision achieved for an ADC?

I was browsing Digikey the other day (don't you?) and I stumbled across some 32bit ADCs, there were offerings from Linear, TI and Analog. One stood out, the AD7177 from Analog which states in Table 7 ...
14
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2answers
7k views

Voltage dividers and ADC's

I want to read a voltage from 0-30V with an MCU ADC which has a maximum input of 3V. Initially I thought of using a 100k-10k divider (so 33V translates to 3V) but according to the answers to ADC ...
13
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5answers
12k views

ADC input impedance on MCUs

What is the input impedance of a typical MCU ADC? In this case I'm working with a PIC24FJ64GA004. I don't need high speed sampling - a maximum of 100 samples per second. I wish to connect a resistive ...
13
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2answers
2k views

Hobby oscilloscope based on AVR. How to remove op-amp noise?

I'm building a hobby oscilloscope on an ATmega16 microcontroller. The main problem is that I receive a large amount of noise while measuring the signal. I used LF353 amplifiers to shift voltage and I ...
12
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6answers
3k views

Design a filter that allows frequencies below 5 kHz to pass freely, but all frequencies above 5.2 kHz must be undetectable

My biggest challenge with this question is its ridiculously steep roll-off rate. I am assuming that the signal is undetectable if its gain is -20 dB. This means that, within the transition band of ...
12
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3answers
37k views

How to make a clean amplified microphone analog to digital conversion?

I've asked a couple of questions relating to this project the past couple of days, but I cant seem to put it all together. I hooked up an electret mic into an opamp and gave output to my arduino ...
12
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4answers
3k views

Use two ADC channels to increase resolution

I need to capture the waveform of a low-amplitude signal that sits on top of a slow-varying, higher-amplitude component. I'm thinking of using an ADC with two channels, and feed one of them with a low-...
12
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2answers
545 views

Straight from the datasheet: Is this really a sensible filter circuit?

Cirrus Logic CS42426-CQZ is an audio CODEC that I want to use in a custom USB sound card. You can download the datasheet from there. On page 61, the datasheet has a recommended circuit for each A/D ...
12
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2answers
3k views

Measuring average current with uC and current shunt

This is my first post. I'm a software guy trying to do hardware so be gentle :) Circuit I'm designing a small circuit (see pic, and sorry for messy schematic) that plain and simply is a bunch of ...
12
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2answers
3k views

How do ADCs fail?

I'm responsible for maintaining a satellite that has an ADC that is failing in an unusual manner. Essentially what is happening is that it toggles back and forth between two values, if the raw voltage ...
11
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6answers
9k views

Cascading ADC's to get higher resolution

Suppose I have a pair of 12-bit ADC's, I can imagine that they can be cascaded to get <= 24-bit output. I can think of simply using one for the positive range and the other for the negative range, ...
11
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1answer
540 views

Design essentials when working with 12bit ADCs

I'm currently designing a board that is attaching a 12bit ADC (MCP3208) to a Raspberry Pi (besides a few other low speed I/O related stuff). It will mostly be attached to analog sensors (temp sensors, ...
11
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1answer
2k views

How could I power an IC over the Ethernet?

I was looking foward to powering a small Integrated Circuit using only the power provided by the ethernet outlet of my room. Is that even possible? I've googled and I've found that the voltage that ...
11
votes
2answers
16k views

What is the purpose of ADC sampling time?

I am trying to understand the usage of ADC sampling time? The ADC I have has a programmable sampling time of 100nsec/500nsec and 1uSec. What is the primary use case of longer sampling time, why ...
10
votes
6answers
19k views

What does a half-digit means in case of accuracy?

I am just wondering what does it mean when somone says something like"3 and 1/2 digit" in case of accuracy of test equipments (or maybe A/D converters). Can somone explain this a bit with some numbers ...
10
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6answers
7k views

How do I sample a -2 V to +2 V analog signal with a PIC microcontroller?

I am using a PIC micro with a 10bit ADC to take readings from an analog signal with a frequency less than 300 hz. However that analog signal is in the range of -2 V and +2 V. How can I condition the ...
10
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2answers
4k views

Adding an anti-aliasing filter to op-amp before ADC

I am designing a circuit that is intended to capture audio samples from multiple channels for sound source localisation. Each channel has the following 2 stage op-amp circuit, before going into a ...
10
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2answers
3k views

What to do with unused analog inputs?

I am working on an application using ATmega328p atmel microcontroller. I started with the 28 PDIP version, but now I want to use the 32 TQFP, which I noticed has 2 extra inputs after compiling my ...
10
votes
4answers
63k views

STM32 ADC conversion using HAL

I am trying to learn how to use "new" HAL library from stm32. When I try to do simple ADC conversion it works just one time, but then it stops converting. I suppose End of conversion flag does not get ...
10
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2answers
10k views

ATMega328 External AREF Connection

From the ATMega328 datasheet, section 24.9.1: The internal voltage reference options may not be used if an external reference voltage is being applied to the AREF pin. From the Arduino reference ...
10
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2answers
3k views

Reducing electrical noise induced from a small DC electrical fan

What's a canonical method for reducing / eliminating electrical noise induced in ADC from a small brushless DC fan? For reference below, I'm also using this wall-wart and this 5V linear regulator. My ...
10
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2answers
3k views

Grounding of ADC grounds

Fast, high resolution ADCs, especially ones that have parallel output, usually have a separate supply pin (DRVDD, (drive vdd) or OVDD (output vdd)) presumably because they don't want to couple noise ...
9
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10answers
5k views

Why can't you just average ADC samples to get more resolution from an ADC?

I'm trying to get more than 10 bits of precision from my Arduino ADC but I can't really figure out the theory behind it. An often quoted Atmel Application note (http://www.atmel.com/Images/doc8003.pdf)...
9
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4answers
4k views

Use Cases for an External ADC

Most Microcontrollers (uC) have an Analog to Digital Converter (ADC) as part of their peripheral set, which is phenomenal as this integrates two components into a single package. These ADCs are ...
9
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2answers
916 views

Can someone explain this microcontroller ADC interface (for reading solar panel voltage)?

I am trying to understand the functionality of a circuit found in TIDA-00121 (you can download the design file from here) I assume that this has to do with the fact that the PV is not directly tied ...
9
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4answers
3k views

Sensing DC motor current

I am allowing the current through a DC motor to flow through a small resistor and measuring the voltage across it. I need to give this analog Voltage to an ADC of micro-controller to do some signal ...
9
votes
2answers
694 views

What would cause this kind of amplitude interference on my ADC recording?

I am using a 12-bit 6.4Mhz ADC to record a sensor reading. It's an ultrasound doppler system. A DAC is used to generate a TX frequency, that frequency is bounced off a moving target and received via ...
9
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2answers
3k views

MCP3424, how to read channels in parallel?

About this question I do not have an electronics engineering background, and this is one of my first challenges with communicating via I2C, and with writing to a register, so please do not assume too ...
9
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2answers
8k views

Arduino has an input value in disconnected pin

I'm new to arduino. Maybe is an elemental question... If I load this program: ...
9
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3answers
3k views

Why do audio op amps require such high rail voltages?

This might be a silly question, but I haven't been able to find it addressed directly anywhere on the internet yet. I also have a handful of related questions in-line, which I hope don't stray too ...
9
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5answers
3k views

High Resolution ADC for Noisy Sensors in Variable Conditions

Intro In response to this question about adaptive amplifiers, It was recommended that in order to deal with variable conditions, it may be more economical to simply use an ADC with higher resolution ...
9
votes
1answer
8k views

Measuring light levels with a photodiode and an ADC

I'm trying to use a photodiode to measure light levels via an ADC on an ATMega168. I've got the microcontroller code working properly (measuring values on a pin and reporting it as an led brightness) ...
9
votes
2answers
2k views

Bluetooth simple oscilloscope

I was thinking to make a simple oscilloscope which can measure at least 2MHz signals, that would be enough, and it will be connected to a PC, or Android device. First, I tought to use USB to connect ...
9
votes
2answers
23k views

Measuring an Arduino's power source voltage using Analog In

I am powering an Arduino using a 5v battery (3.7v to a step-up module), and I need to measure the voltage. Let's say the battery delivers high current, is it safe to measure the voltage via Analog In? ...

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