Drift correction

The use of multiple synchronized lock-in channels helps to reduce errors introduced due to unstable system conditions, such as current noise, temperature drift or parameter changes before steady-state conditions are reached.

Current noise is often the predominant source of noise in transport measurements and is introduced by different means, including output noise from a voltage/current source, inductive pick-up or rectification of radiofrequency interference. In a simple closed circuit, both current and current noise are equal at all points of the loop, and the current noise affects both the current measurement and the device under test. If both current and voltage are measured synchronized, both are well correlated with the only unknowns being the resistance of the current measurement shunt/feedback resistor and the resistance of the device under test.

Temperature drift is often an unavoidable source of error. The design of stabilization systems is a balance between having gradients between thermometer and sample (thermometer overheating) or long time constants. Measuring both the device under test (for example a sensor) together with the device temperature, the quality of the data can be improved significantly using the temperature dependence of the device. Similarly, other environmental parameters such as magnetic field, laser power, strain or pressure that can have an impact on the device under test can be monitored and corrected for synchronously.