Conventional value of volt-90

$V_{90}$ = 1.000 000 106 66… V

Value: 1.000 000 106 66… V
Standard uncertainty: exact
Relative uncertainty: exact
Status: Exact
Symbol: $V_{90}$
Source: CODATA 2022 via NIST · NIST entry

NIST prints this exact value cut to 12 digits. ConstantID recomputes it from the defining constants: 1.000 000 106 665 107 250 590 448 942 97…

Use in a calculation

# conventional value of volt-90, CODATA 2022 (NIST)
conventional_value_of_volt_90 = 1.0000001066651072505904489429721642  # V, exact

# SciPy: scipy.constants.physical_constants['conventional value of volt-90']

What it is

The size of the practical volt used in electrical metrology from 1990 to 2019 (based on K_J-90 and R_K-90), in SI volts. It is exact because the elementary charge and Planck constant are now exact.

It is built only from constants with exact values, so it is exact too.

In other units

Unit	Value
mV millivolt	1000.000 107	exact
kV kilovolt	0.001 000 000 107	exact
statV statvolt	0.003 335 641 308	exact

Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display.

How the value changed, 1998–2022

CODATA	Value (uncertainty)	Relative uncertainty	Change from previous
2022	1.000 000 106 66…	exact	exact
2018	1.000 000 106 66…	exact

“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).