Author: burkard

# Galvani manual

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- Performing measurements
- Data evaluation
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## Data evaluation

Evaluation can be processed after termination of a measurement or after reading measurement data from file.
Choose Evaluation/Data in the menu. A window Data evaluation is shown.

Enlarge a part of the diagram (zoom)

When data evaluation is started, the coordinates of the mouse pointer are shown in the display.
Drag a frame on the diagram in order to select it. It will be enlarged to the whole diagram area. Galvani smoothens the limits of the coordinate system.
Click the tool button to return to the original coordinate system.

Data transformation (conversion of x- and y-values)

Galvani provides several calculation procedures which are common for evaluation of measurement diagrams. These procedures can be combined.
Measurement data are not modified in this process. If the conversion is cancelled, measurement data are shown in their original state. Also, the measurement function itself is restored.

Titration volume

Time variable is converted to volume (seconds -> milliliter). This transformation is suitable for volumetric analyses (titrations). You have tu use a titration pump or constant velocity burrete in order to have constant volume speed.

- Turn on the switch Titrator volume.
- The volume speed of the burette (must be determined in a preliminary experiment) is adjusted in the input field (unit ml/min).
- Confirm with OK.

On the diagram's x-axis the variable volume is shown (unit milliliter).

Voltage of a thermocouple

This function can only be used with a measurement function "DC voltage" in the selected channel.
The measured voltage of the thermocouple (copper/constantan and nickel/chrome nickel thermocouples are supported) is converted to temperature difference (in kelvin, shown in °C). Thermocouples are suitable for exact measurement of temperature differences if a high-resolution digital multimeter (resolution in microvolt) is used. 1 °C corresponds to 39 µV voltage for a copper/constantan or nickel/chrome nickel thermocouple. This value is temperature dependent, the slope is not linear. Galvani calculates the temperature difference from voltage with a polynomial interpolation with an accuracy of +/- 0,01 °C in the range of 0 °C to 100 °C.
The second thermocouple must be held on a constant temperature (e.g. with melting ice at 0 °C) in order to measure temperature values instead of differences.

- Select Cu/CuNi for copper/constantan resp. Ni/NiCr for nickel/chrom nickel in the choose box Thermocouple.
- Confirm with OK.

On the diagram's y-axis the variable temperature is shown (unit °C).

Inverse (reciprocal values)

Corresponding to data transformation x -> 1/x

- Turn on the switch Inversion.
- Confirm with OK.

The function resistance (uni ohm) is altered to function conductivity (unit siemens) and vice versa. In all other cases the expression "1/" is shown as a function resp. unit prefix in the diagram.

Logarithm (base 10)

Corresponding to data transformation x -> log x

- Turn on the switch Logarithm.
- Confirm with OK.

The expression "log" is shown as a function resp. unit prefix in the diagram.

functions

function graph

A mouse click on the area opens a colour selection window where the colour of the function graph can be chosen.

Linear regression

After turning on this switch a linear regression of measurement data is processed.
The results (slope and intercept of the straight line) are shown and the calculated straight line is shown in the diagram.

Differential function

After turning on this switch the first derivative of the data function is calculated. Differential quotients are calculated by building averages. Galvani detects function maxima by building moving averages and fits them to a gauss model by calculating least squares. Galvani reports the maxima of the derivative and shows differential quotients as data points and the function graph (gauss model) in the diagram. From the differential function turning points (titration curves) of the data function can be detected.

Peak-Integration

After turning on this switch peaks in the course of data are detected. This function is suitable for evaluation of chromatograms.
Galvani reports a table with x-coordinates of peak maxima (retention time), peak area (substance amount) and percentage of the area.
As an option peak area, peak limits and the baseline of the chromatogramm can be shown.