# Questions tagged [adc]

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

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### 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. ...
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### 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 ...
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### 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 ...
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### Combined ADC scaling and offset with variable input voltage ranges

I am trying to create a circuit which will allow me to scale and offset a voltage (be it AC or DC) to within the range of the Arduino ADC. The voltage could be anything between + and - 250V, but I ...
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### Measure PIC's own VDD-in voltage with ADC

Processor: PIC18F66K22 Compiler: C18 (XC8 is fine also) I've just made (and succesfully tested) code to measure the voltage on AN4 analog pin. Now I want to try something else, not quite sure if it'...
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### What is the function of this circuit?

Just wondering if someone can give me an explanation for this capacitor layout - what is it's function? The chip to the right is an ADC. Circled in blue. I'm guessing it is well known but i don't ...
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### 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 ...
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### Required output impedance for ADC input?

On the Atmel ATmega328P on the Arduino Uno, the ADC RAIN value is 100 MΩ - which I assume is the ADC input impedance. However, in the datasheet it says "The ADC is optimized for analog signals ...
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### SPI slave randomly missing bits in response

I've connected an MCP3008 to a raspberry pi. First on a solderless breadboard, where everything worked correctly. Then on a prototyping board, where the only difference is that the chip is externally ...
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### Over voltage and reverse voltage protection of multiplexed ADC with voltage follower

I am designing a protection circuit for the ADC section of a design I am working on. There will be 8 analog signals being read by a single pin of the MCU via an 8 channel multiplexer. The analog ...
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### 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 ...
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### Analog-Digital converter's LSB formula

What is the correct definition of the LSB voltage for an analog to digital converter? I have found two formulas: LSB = FS / (2N) LSB = FS / (2N - 1) N ... resolution in bits of the ADC. FS ... ...
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### How to remove noise in ADC voltage measurement?

I want to measure the open circuit voltage of a battery cell (differential reading, that is A0-A1). In order to do that, I am using an industrial PLC based in Arduino Mega and a cheap but accurate ADC ...
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### What is the purpose of this op amp?

I am trying to build a pH meter using the below circuit. I am trying to understand the function of Op Amp U1. As I understand it, the LM4140A-1.0 is a voltage reference outputting 1.024V, which is ...
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### Can I use a UA741 here?

I need to pass a domestic -10dbV audio signal (it should oscillates between -447mV and +447mV) to a microcontroller's ADC which only accepts signals that oscillates between 0V and 5V. I think that the ...
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### 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 ...
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### 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 ...
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### Implement MicroController Power Switch and re-use the button for other features

This is similar to other questions, but I feel it is different because of the reuse of the "power" button. I want a "latching" Momentary Power button. Behavior: User Pushes momentary button, holds ...
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### PIC - How to skirt around low maximum ADC input impedance?

Reading a 9V battery on a PIC is nothing new. The most simple and straightforward way is with a voltage divider. I'd like to keep the divider resistances cranked up into the hundreds of kohms so I'm ...
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### RC Lowpass Filter between Amplifier and ADC input

I have sensors (pyranometers that consist of thermopiles and measure sun irradiation) that ouput a low voltage signal so I need to amplify them using an instrumentation amplifier. I have chosen the ...
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### Reading internal temperature sensor STM32

I'm trying to read internal temperature sensor. Each time, the value from ADC conversion is 296 which results in negative temperature. Should I add something to the code below, enable some peripheral ...
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### How to measure battery voltage

I am building a battery powered device. Almost all of my logic is running at 3.3v, although I do have a 5v supply for a few hobby servos. I want to measure the battery voltage, but I can't do so ...
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### Circuit design for converting sensor input to desired output range

As part of my project, I am tasked with designing a circuit that can accurately convert a voltage signal in the range of -300 mV to 300 mV, obtained from a sensor to a voltage signal in the range of 0 ...
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### ADC input protection?

I need to sample an analog voltage from a sensor (0-12v) in an environment where large voltage spikes may be induced in the transmission line, what's the best (simple and cheap) method of protecting ...
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### ADC for measuring 0-5V but connected to 3.3V device

I have a BeagleBone (BB) and want to connect the analog output of a motor controller to it. The motor controller creates an output in the range of -4V to +4V and the BB anlog inputs only accept ...
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### Measure both positive and negative voltages using ADC

I am looking into measuring both positive and negative voltages using ADC. My input voltage is in range from -55 to +55V, which is total of 110V. ADC I am using is MCP3424, since it is relatively easy ...
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### What does a High Impedance input mean for an ADC

The ADC ADS131M08 list a feature: Can someone elaborate what this feature implies? Does this mean i can place a 300 Kohm resistor in series with the inputs? There is even a reference on page 88 with ...
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### ADC first transition at 1/2 LSB - is that not a non-linearity?

[From Analog Devices Data Converter Handbook] I understand why they chose to place the first transition at the 1/2 LSB point but does that not cause non-linearity?, since you basically have reduced ...
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### Negative Voltage Level Shifting to an ADC

I am currently building a project that uses an AD595 analog devices chip to linearize the output of the Thermocouple sensor to 10mv/deg C. This output is to be connected to the ADC input of a Zigbee ...
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### Low Current Battery Monitor Detail Question

I'm trying to design a circuit that will be running from a battery. I'm currently working on the part that detects the voltage and came across this question (and answers) here: It made pretty good ...
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### How a Delta-Sigma Modulator Works

Can someone explain in simple terms how a delta-sigma modulator works specifically for ADC applications? I've googled around and have been piecing it together but am still unclear on a few things. ...
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### Can I estimate remaining battery life by measuring its voltage with the same MCU that it powers?

I'd like to estimate the remaining battery life of a battery that powers a microcontroller. Could I accomplish this by simply leading the battery into the MCU's built-in ADC? My idea is that I could ...
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### Voltage translation: 5V to 3.3V analog

I need to translate 0-5V analog signal from CASR 50-NP to 0-3.3V analog signal for the MCU's ADC. I came along Microchip's tip #16 solution. Is this a good practice? Can someone verify my design?
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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, ...
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### 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 ...
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### 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 ...
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### 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 ...
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### Divider and lowpass combined

I am using the following circuit for two purposes: As a voltage divider, to reduce DC sensor output to a range suitable for my ADC. As a lowpass filter, to remove high frequency noise from the signal....
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### 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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### Arduino has an input value in disconnected pin

I'm new to arduino. Maybe is an elemental question... If I load this program: ...
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### What value to use to convert ADC value to voltage?

While working on my project, I got to a point where I don't know the answer. I have a 10-bit ADC (the one incorporated in the ATMEGA328P) and it returns values up to 1023 (210 - 1). The official ...
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### In an ADC what are the units of resolution called?

I have a signal whose full scale output on the 12bit ADC is 4095. If I reduce the signal so I see the output number is (say) 4000 the output has decreased by 95. But 95 what? What are those divisions ...
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### Easiest way to go from analog input to PWM output?

Project background: I'm building a plasma speaker. There are several examples online using a TL494 power supply IC and feeding audio into its feedback pin to get sound out. A sample schematic: I'...
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### Use the oversamplling followed by the "decimation method" to increase the ADC resolution and not normal averaging

To increase the 12-bit resolution of ADC from 12 bit to 14 bit, this can be done through the 'oversampling and decimation method'. An Atmel Application note says that The higher the number of samples ...
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### High Voltage differential Measurement

Suppose I want to measure individual cell voltage of a 12-serial-cell battery pack, what would be my most economical options? Single cell voltage is 3V-4.2V but the stack can be between 2-12 cells ...
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