Microampere to Coulomb per second
μA
C/s
Conversion History
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Quick Reference Table (Microampere to Coulomb per second)
| Microampere (μA) | Coulomb per second (C/s) |
|---|---|
| 1 | 0.000001 |
| 10 | 0.00001 |
| 50 | 0.00005 |
| 100 | 0.0001 |
| 500 | 0.0005 |
| 1,000 | 0.001 |
About Microampere (μA)
The microampere (μA) equals one millionth of an ampere (10⁻⁶ A) and is the standard unit for quiescent and standby currents in battery-powered electronics. Operational amplifier input bias currents, photodiode outputs under dim light, and EEG scalp electrode signals all fall in the microampere range. Many modern microcontrollers in low-power run mode consume under 100 μA, enabling coin-cell operation for months. Analytical instruments such as pH meters and reference electrodes operate at microampere levels to avoid disturbing the solution being measured. Implantable cardiac pacemakers deliver stimulation pulses of several hundred microamperes.
A cardiac pacemaker delivers stimulation pulses of roughly 100–500 μA. A modern ARM microcontroller in active low-power mode draws around 50–200 μA.
About Coulomb per second (C/s)
The coulomb per second (C/s) is a derived SI expression for electric current that makes the physical definition explicit: one ampere is exactly one coulomb of charge passing a point per second. The relationship I = Q/t links current (A), charge (C), and time (s). While C/s and A are numerically identical and dimensionally equivalent, the C/s form appears in physics textbooks and dimensional analyses where the derivation from charge and time is instructive rather than treating the ampere as primitive. In calculations tracking charge accumulation — capacitor discharge, electroplating, or battery coulomb-counting — expressing current in C/s clarifies the unit chain.
A capacitor delivering 1 C of charge over 1 second discharges at exactly 1 C/s = 1 A. A 500 mA USB charger transfers 0.5 C of charge each second.
Microampere – Frequently Asked Questions
How long can a coin cell battery last at microampere currents?
A CR2032 coin cell has about 225 mAh capacity. At 10 μA continuous draw, it lasts roughly 225,000 / 10 = 22,500 hours — about 2.5 years. At 1 μA, theoretical life exceeds 25 years, though self-discharge limits practical life to about 10 years.
Can microampere currents be dangerous to humans?
Not from shock — the perception threshold is about 500 μA (0.5 mA) for DC and 1,000 μA for AC at 60 Hz. However, microampere currents applied directly to the heart (e.g., through a catheter) can cause ventricular fibrillation at as little as 50–100 μA, which is why medical device safety standards are so strict.
Why do pH meters need to operate at microampere levels?
A glass pH electrode has an internal resistance of 10–1,000 megaohms. Drawing more than a few microamperes would cause voltage drops across this resistance, shifting the reading. Modern pH meters use high-input-impedance amplifiers that draw under 1 μA to avoid disturbing the electrochemical potential being measured.
What is quiescent current and why is it measured in microamperes?
Quiescent current (Iq) is what an IC draws when powered on but doing nothing — no signal processing, no load driving. For battery-powered designs, low Iq is critical. A voltage regulator with 1 μA Iq wastes far less standby power than one with 100 μA, directly extending battery life in always-on devices.
How does a pacemaker deliver just a few hundred microamperes so precisely?
Pacemakers use constant-current output stages that regulate pulse amplitude to within ±5 μA. The pulse is typically 100–500 μA for 0.4–1.5 ms, just enough to depolarise heart tissue and trigger a contraction. Modern devices automatically adjust the current to the minimum needed, conserving the battery for its 8–12 year design life.
Coulomb per second – Frequently Asked Questions
Why bother writing coulombs per second when it is just amperes?
In dimensional analysis and physics derivations, C/s makes the relationship between charge and current explicit. When you are computing how much silver an electroplating bath deposits (Faraday's law), writing current as C/s reminds you that charge = current × time, which directly gives the mass deposited.
How many electrons is one coulomb?
One coulomb is approximately 6.242 × 10¹⁸ electrons — about 6.2 quintillion. At 1 C/s (1 A), that many electrons pass a point in your wire every single second. A USB cable charging your phone at 2 A carries 12.5 quintillion electrons per second. The numbers are staggering but the charges are tiny.
Is coulombs per second used in any real-world instrument or specification?
Not directly — every instrument reads in amperes or milliamperes. But coulomb-counting battery fuel gauges internally track charge in coulombs by integrating current over time: ∫I dt. The C/s framing appears in battery management system firmware and electrochemistry literature where charge balance matters.
How does Faraday's law of electrolysis use coulombs to predict metal deposition?
Faraday discovered that the mass of metal deposited at an electrode is directly proportional to the total charge passed (in coulombs). For silver, 107.87 grams deposit per 96,485 C (one Faraday). So a 10 A electroplating bath running for 1 hour passes 36,000 C and deposits about 40 g of silver. Thinking in C/s makes the calculation: current × time × atomic weight / (valence × 96,485).
How does coulomb counting work in battery management systems?
A shunt resistor or Hall sensor continuously measures current flowing in and out of the battery. The BMS integrates this current over time (summing C/s × Δt) to track net charge. Drift and measurement errors accumulate, so smart BMS designs periodically recalibrate against voltage-based state-of-charge estimates.