Calculator Inputs
Enter the digital ADC reading and signal chain settings. The calculator supports unipolar, offset-binary, and two’s-complement readings.
Voltage Graph
The graph shows estimated source voltage across the ADC code range using the current settings.
Formula Used
Unipolar ADC
Max Code = 2N - 1
ADC Pin Voltage = ADC Code × Vref / Denominator
Bipolar ADC
Two’s Complement Signed Code = Code - 2N, when Code ≥ 2N-1
ADC Pin Voltage = Signed Code × Vref / Denominator
Signal Chain Correction
Source Voltage = (Calibrated ADC Voltage - Offset) / (Gain × Divider Ratio)
Quantization Uncertainty = ±0.5 × Source LSB Size
How to Use This Calculator
- Enter the ADC code from your microcontroller, data logger, or converter.
- Select the code format. Auto mode accepts decimal, hexadecimal, and binary values.
- Enter the ADC resolution and reference voltage.
- Choose unipolar, offset-binary, or two’s-complement mode.
- Add gain, divider ratio, offset, and calibration values if your circuit uses them.
- Press the calculate button. Results appear above the form.
- Review the graph, then download the CSV or PDF report.
Example Data Table
| ADC Bits | Vref | ADC Code | Mode | Approx Voltage | Typical Use |
|---|---|---|---|---|---|
| 10 | 5.0 V | 512 | Unipolar | 2.502 V | Arduino sensor reading |
| 12 | 3.3 V | 2048 | Unipolar | 1.650 V | Microcontroller input |
| 16 | 2.5 V | 32768 | Offset binary | 0.000 V | Precision bipolar input |
| 24 | 2.048 V | 0x400000 | Two’s complement | 1.024 V | High-resolution measurement |
ADC to Voltage Conversion Guide
Why ADC Voltage Matters
An analog to digital converter changes a real voltage into a digital number. That number is useful only when its scale is known. This calculator converts the count back into voltage. It also includes circuit corrections. These corrections help when sensors use dividers, amplifiers, or offsets.
Resolution and Reference
ADC resolution defines how many steps are available. A 12 bit converter has 4096 possible codes. The reference voltage defines the top measurement range. A higher reference covers more voltage. A lower reference gives smaller step size. Step size is often called the LSB. Smaller LSB values improve measurement detail.
Unipolar and Bipolar Readings
Many microcontrollers use unipolar ADC inputs. Their codes start at zero volts. The largest code is near the reference voltage. Precision converters may use bipolar coding. Bipolar readings can represent negative and positive inputs. Offset binary places zero near the center code. Two’s complement uses signed digital math.
Gain, Divider, and Offset
Real circuits often change the signal before conversion. A divider lowers high voltage for safe measurement. An amplifier increases small signals. An offset shifts the signal into the ADC range. This calculator reverses those changes. It reports the estimated source voltage. It also shows the ADC pin voltage.
Calibration and Error
Calibration improves practical accuracy. The slope value corrects scale error. The intercept value corrects fixed voltage error. Quantization uncertainty is also shown. It is based on half of one source LSB. Use this value as a basic digital resolution limit. For final designs, also include reference tolerance. Add input noise and component tolerance too.
FAQs
1. What is an ADC count?
An ADC count is the digital number produced by the converter. It represents where the measured voltage sits within the selected reference range and resolution.
2. What does Vref mean?
Vref is the reference voltage used by the ADC. It sets the scale for conversion. A stable reference gives more reliable voltage readings.
3. Should I use 2^N or 2^N minus 1?
Both conventions appear in datasheets. Endpoint conversion uses 2^N minus 1. Ideal LSB conversion uses 2^N. Match the method to your ADC documentation.
4. What is ADC resolution?
Resolution is the number of digital bits available. More bits create more codes. This gives smaller voltage steps and finer measurement detail.
5. What is divider ratio?
Divider ratio is the fraction of source voltage reaching the ADC pin. For example, 0.5 means the ADC sees half of the source voltage.
6. What is input gain?
Input gain is amplification before the ADC. A gain of 2 means the ADC pin receives twice the original signal before conversion.
7. Why is quantization uncertainty shown?
An ADC cannot show values between digital steps. Half of one LSB is a simple estimate of the unavoidable rounding uncertainty.
8. Can this calculator handle negative voltages?
Yes. Select offset-binary or two’s-complement mode for bipolar ADC values. Make sure your hardware and reference range support that measurement type.