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Convert volts, millivolts, kilovolts, and microvolts. For electronics, electrical engineering, and circuit design.
Voltage is the electric potential difference between two points. The SI unit is the volt (V), defined as the potential difference that drives one ampere of current through a resistance of one ohm (from Ohm's Law: V = IR). All voltage conversion is pure decimal scaling, which makes it simpler than units like temperature that require additive offsets.
The millivolt (mV) is one thousandth of a volt (1 mV = 0.001 V). It is the working unit in low-level signal electronics. Thermocouple sensors generate signals in the millivolt range, typically 0-80 mV for type K thermocouples across their full temperature range. Electrocardiogram (ECG) signals measure cardiac electrical activity at roughly 1-2 mV peak amplitude. Strain gauge bridges and load cells output millivolt signals that require amplification before processing.
The microvolt (µV) is one millionth of a volt (1 µV = 0.000001 V). Signals at this scale are found in EEG (brain wave) measurements, where typical cortical signals are 10-100 µV. Precision measurement instruments, low-noise amplifiers, and seismic sensors all work in the microvolt range. Shielding, ground plane design, and careful PCB layout are required to prevent noise from overwhelming signals at this scale.
The kilovolt (kV) is one thousand volts. High-voltage applications include power transmission lines (typically 66 kV to 765 kV in transmission networks), industrial X-ray machines, cathode ray tubes, and electrostatic precipitators. High-voltage work requires specialised safety procedures and equipment rated for the voltage class involved.
In digital electronics, logic levels are expressed in volts. Standard TTL logic uses 0 V (logic low) and 5 V (logic high). Modern microcontrollers and FPGAs operate at 3.3 V or lower to reduce power consumption and heat. Level shifting circuits are needed when interfacing 3.3 V and 5 V devices in the same system.
Power transmission uses high voltage to minimise resistive losses. The power lost in a transmission line is P_loss = I² × R. By stepping voltage up using transformers (and stepping current down proportionally), the same power can be transmitted at a fraction of the current, reducing losses dramatically. A transmission line operating at 400 kV carries the same power as one at 33 kV but with about 147 times less resistive loss.
How many millivolts are in a volt?
Exactly 1,000 millivolts equal one volt. 1 V = 1,000 mV = 1,000,000 µV = 0.001 kV. All voltage conversion is multiplication or division by powers of 1,000.
Why do some sensors output millivolts instead of volts?
Physical phenomena like thermal gradients, strain, and biological potentials generate small amounts of electrical energy. The resulting signals are naturally in the millivolt or microvolt range before amplification. Amplifiers (op-amps, instrumentation amplifiers) step these signals up to a range suitable for analogue-to-digital conversion, typically 0-3.3 V or 0-5 V.
What is the difference between AC voltage and DC voltage?
DC (direct current) voltage is constant in polarity and magnitude, like a battery. AC (alternating current) voltage reverses polarity at a fixed frequency, typically 50 Hz in Europe and 60 Hz in North America. Mains power is AC. The 230 V or 120 V on a wall socket is an RMS (root mean square) value; the peak voltage is higher (about 325 V for 230 V mains). Unit conversion between volts, millivolts, and kilovolts applies to both AC and DC values.