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Engineering Calculators

Sensing RC Filter Designer

Design and evaluate a first-order RC filter for voltage, current, and temperature sensing.

Check useful-signal attenuation, high-frequency noise rejection, phase delay, and response speed.

Standalone first-order RC model

Inputs

Signal Source
kΩ
kΩ

Used for bus, input/output, battery-voltage, and NTC-divider sensing. Source resistance is calculated as Rupper || Rlower.

RC Filter

kΩ
pF

Frequency Conditions

kHz

The highest useful measurement or control frequency that should be preserved.

MHz

A switching-noise, ringing, or other dominant high-frequency interference component.

dB

Maximum acceptable attenuation at the selected signal frequency.

dB

Positive target value. The response result is shown as a negative dB gain.

Calculated Response

First-order RC low-pass filter

GOOD BALANCE
Signal source to Rfilter and Cfilter sense node Resistor divider Rsource = 4.75 kΩ Rfilter Sense node Cfilter ADC / controller input Ideal first-order RC model No internal ADC model

The useful signal is preserved while the selected noise frequency is attenuated.

The current RC values meet both targets.

Cutoff Frequency 1.26 MHz τ = 127 ns
Noise Attenuation -38.01 dB At 100 MHz
Signal Attenuation 0.00 dB At 10.0 kHz
Signal Phase Delay -0.5° First-order phase lag
10-90% Rise Time 278 ns Approximately 2.2τ
1% Settling Time 582 ns Approximately 4.6τ

Frequency Response

Log-frequency magnitude and phase response with fc, signal, and noise markers.

Magnitude Response Gain in dB
Phase Response Degrees

Engineering Details

Source Resistance4.75 kΩ Total Resistance5.75 kΩ Time Constant127 ns 0.1% Settling Time873 ns Signal Amplitude Ratio100.00% Noise Amplitude Ratio1.257% Signal Frequency / Cutoff0.00795× Noise Frequency / Cutoff79.5×

How to Use

Choose the source type, enter the source resistance information, then set the series filter resistor and shunt capacitor.

Use the signal frequency for the highest useful measurement or control content that should be preserved.

Use the noise frequency for a switching component, ringing frequency, or other high-frequency interference to attenuate.

This tool uses an ideal first-order RC model. Sensor bandwidth, amplifier stability, ADC input loading, PCB parasitics, and nonlinear effects are not included.