LCRmeter

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Usage

Sweep mode vs. Step mode

The LCRmeter provides two modes to vary any apply parameters. The Sweep mode is similar to the Sweep mode that can be found in many other modules. For a capacitance-voltage (CV) curve one would use "Voltage" as Sweep mode while a capacitance-frequency (Cf) curve is obtained by using "Frequency" as Sweep mode. The Sweep values that are successively applied to the sample are typically created via the Sweep editor that comes with LCRmeter module.

The Step mode, depending on the Device Class, can be used to create a further parameter variation. For example, capacitance-freqeuncy curves are often measured at different bias voltage. Thus, one would change Step mode to "Voltage". The Step values, however, cannot be created by the internal Sweep editor of the LCRmeter module. For that reason, one can add a module named 'Sweep' to the sequencer just one level higher than the LCR meter. Now, the values defined in that module can be handed over to the LCRmeter module by selecting "Sweep value of <label of the module" as source for the Step value. Why is that so? By having different origins for the values for Sweep value and Step value, one can create sequencer procedure where MakeFile is embedded such a way that a new file is created for each step, but not for each sweep.


Device class programming

Specialties

Each Device Class for the LCRmeter module must return the first three variables as following:

  1. "R" the real part of the impedance R,
  2. "X" the imaginary part of the impedance X, and
  3. "Frequency", the frequency

If this is the case, the Device Class is accepted.

Calculation

The LCRmeter module automatically calculates the capacitance, absolute impedance (modulus), and phase, and appends it to the measured values. The formulas used are as given below. Please note that you always can check the correct calculation by doing it on your own to scientifically verify the results.

Absolute impedance (modulus) in V/A

|Z| = (R**2 + X**2)**0.5

Capacitance in F

C = -X/2.0/math.pi/f/|Z|**2

Phase in degree

Phi = math.atan(X/R)/math.pi*180.0

These values are calculated for reasons of convenience. We recommend to calculate the capacitance value on your own as it highly depends on the model and the corresponding interpretation of the circuit that comes with each sample under investigation.


Supported parameters

SweepMode

A ComboBox with the currently selected Sweep mode.

StepMode

A ComboBox with the currently selected Step mode.

ValueTypeRMS

A ComboBox that can be used to define different options for the AC signal. For example, most LCRmeter can apply either a current or a voltage signal. If there is only possible

ValueRMS

A LineEdit with the value of the selected type in ValueTypeRMS.

ALC

A ComboBox to present different modes for Automatic Level Control (ALC). ALC makes sure that the correct signal is applied to the device under test. Caution: If one of the measurement ports is not correctly connected to the device, the LCRmeter might apply higher voltages than desired.

Integration

A ComboBox to provide different integration modi.

Average

A ComboBox to provide different average modi or a number of averages.

Trigger

A ComboBox to choose the source of the trigger signal.