Ratiometers
Ratiometers are measuring instruments specialising in the comparison of two electrical signals, generally used to determine the transformation ratio of transformers (primary voltage vs. secondary voltage). They enable the conversion ratio of a winding to be measured with ppm accuracy, while eliminating systematic errors by direct comparison. This type of analysis is essential for testing power, instrumentation and distribution transformers. In metrology, certain models of high-precision ratiometers are also used to compare standards or resistive dividers as part of ISO 17025 traceable calibration campaigns.
Modern digital instruments offer resolutions of 0.1 ppm, linearity better than ±0.005 %, and self-calibration functions. Their high input impedance guarantees measurement without circuit disturbance, and GPIB or LAN interfaces make them easy to integrate into automated test benches.
An essential diagnostic tool for transformer manufacturers and maintainers, the ratiometer can be used to check the nominal ratio, monitor drift and validate electrical compliance in an industrial environment.
concrete questions about Ratiometers
01
What is a ratiometer used for?A ratiometer measures the ratio between two electrical quantities - usually two voltages or two resistors. It is used to compare signals, monitor relative drift, validate measurement bridge ratios or control sensors whose output is proportional to an internal reference.
02
What's the difference with a conventional voltmeter?A voltmeter measures an absolute value. A ratiometer measures a ratio (V1/V2), which gives much greater accuracy when the two quantities drift in a similar way. This approach greatly reduces the errors associated with the absolute stability of the measurement system.
03
What are the typical uses in laboratories and metrology?They are used to calibrate resistor bridges, check ratiometric sensors, monitor relative variations in analogue circuits, compare voltage references, or analyse the stability of a device by minimising the influence of temperature and background noise.
04
Why do ratiometers offer high measurement stability?Because they cancel out a large proportion of the drift common to the two signals being compared. Thermal variations, source noise or assembly instabilities affect the two channels in a similar way, so they have less impact on the measured ratio.
05
What technical criteria should you check before choosing one?Relative accuracy, long-term stability, ratio range, input impedance, filtering capabilities, thermal drift and compatibility with the references or sensors used. For demanding measurements, time stability and channel isolation are crucial.
