3.6. Advanced Measurement Operation
To configure advanced settings, scroll down to the advanced section, and tap it to expand.
Figure 3.17 Advanced lock-in settings
High-Pass Digital Filter
When this filter is enabled, a high-pass filter is applied to the lock-in readings before demodulation. The corner frequency of the filter adjusts automatically such that the response time of the lock-in measurement is not affected. The gain and phase of the filter is also compensated to avoid affecting the measurement. The filter is effective at reducing noise when measuring lock-in signals with large DC components, especially at low frequencies.
Interface Command: SENSe#:DIGital:FILTer:HPASs[:STATe]
Dark Mode
If dark mode is enabled, the indicator LEDs on the front of the module will be turned off.
Interface Command: SENSe#:DMODe
Calculated Resistance
The M81-SSM performs resistance calculations between a measure module and a selected source module.
By tapping the omega (Ω) in the upper right hand corner of any measure module’s readings banner, it is possible to view the calulated resistance when the measure module is in either DC or lock-in mode. To exit resistance view, either the three dots can be tapped to select the desired view, or the reading symbol can be tapped to return to the default view.
The source module being used to calculate resistance can be changed by scrolling down to the advanced section, tapping to expand, then selecting resistance source. Calculating a resistance requires one voltage and one current module. Therefore, for a module to be compatible, the source must be a voltage module when the measure is a current module. Similarly, if the measure is a voltage module, the source must be a current module.
Presently, only two resistance calculations are supported. The first calculation requires a source module generating a DC shape with a measure module in DC mode. The second calculation requires a source module generating a sine shape with a measure module in lock-in mode. When in DC mode, the display will show the selected source module’s excitation that is being used in addition to the resistance value. When in lock-in mode, the display will show the selected source module’s excitation and frequency in addition to the resistance value.
In some cases, the resistance value may appear as an error. These error messages can be tapped for more information about what is causing the issue:
S is not connected The selected source module must be connected and loaded.
S is not loaded The selected source module must be connected and loaded.
S is not enabled The source module’s output is disabled. Enable the source to calculate a resistance measurement.
The units of M are not compatible with S One current module and one voltage module are required to calculate a resistance measurement.
The source amplitude is 0 The sourced module’s output is enabled, but has a zero amplitude. Set a nonzero amplitude to calculate a resistance measurement.
M mode is not compatible with S shape The source and measure modules must both be in DC mode, or the source in sine and measure in lock-in. Manually adjust each module’s mode and shape.
S is in error There is an active error on the source module. Check connections and settings to clear the error.
M is in error There is an active error on the measure module. Check connections and settings to clear the error.
Figure 3.18 Lock-in resistance calculation
Relative Measurement
Relative measurements allow the removal of offsets from measured readings that could be introduced by sources external to the experiment. By using the zero button, existing offset will be set into the baseline value which is subtracted from the primary reading being displayed. When a baseline value is set, the zero button will be replaced with a clear button, which will set the baseline value back to zero.
By tapping the 3 dots in the upper right hand corner of the display area, it is possible to select Relative DC or Relative RMS, when in DC or AC modes respectively. The zero and clear button will allow for quick modification of the baseline value, shown in the bottom left of the display. By tapping the baseline value in the display area, a custom baseline value can be set.
Figure 3.19 Relative RMS measurement