Meaning
Specialized voltage measurement devices feature extremely high input resistance to prevent the instrument from drawing current from the circuit under test. A high impedance electrometer is essential for measuring the potential of reference electrodes that have very low exchange current densities. This prevents the measurement process itself from polarizing the electrode and causing an inaccurate reading.
Typical input impedances exceed ten teraohms to ensure the integrity of the delicate electrochemical signals.
Signal Preservation
Electrodes with high internal resistance are susceptible to voltage drops even when minute currents flow through a standard voltmeter. Using a high impedance electrometer eliminates this error by providing a nearly open circuit condition at the probe. This allows for the precise tracking of the open circuit potential over long durations without draining the cell.
Noise Suppression
Shielding and guarded inputs protect the sensitive circuitry from external electromagnetic interference. Because a high impedance electrometer operates with such low current levels, it is highly sensitive to static charge and ambient electronic noise. Laboratory environments use these tools to characterize the passivation layers and corrosion rates of new battery chemistries.
Application Range
These instruments are mandatory for the evaluation of solid state electrolytes and thin film batteries where traditional meters would fail. While a high impedance electrometer is a standard benchtop tool, its size and complexity usually preclude it from being used inside a mobile battery management system. The device serves as the primary standard against which simpler field sensors are calibrated.
