## Calibration

### Which statistical parameters should be taken into account for a comparison of measurement values?

The following parameters are important for a comparison of measurement values: arithmetical mean value, standard deviation, amount of single measurements.

Without the relevant standard deviation and number of single measuremenents, the mean values cannot be compared with each other in a  meaningful manner.

### Why do I need to calibrate?

Each physical measuring method is influenced by the parameters of the coatings and the substrate. These parameters are: parts geometry, electrical conductivity, magnetizability, density of the coating, measuring surface etc.

Each time, when these parameters of coatings or substrate have changed, it is necessary to recalibrate the measurement instrument.

### I am calibrating my measuring instrument on a flat plate. Now I want to measure on a turned part with a small diameter. Will it be OK to proceed, without any further calibration?

No, the calibration on the flat plate causes a systematic measuring error on a curved surface. This means the measuring values will  be too large. This is because the instrument rates the measuring signals of the sample (here: the curved object) in such a manner, as if they were from a flat sample.

### Why may two parties receive different measurement results? What could be the reasons for that?

The accuracy of measuring instruments is ensured by the calibration standards. The calibration must be carried out on real, uncoated samples. Furthermore one must take care to measure on the same measuring positions. It is important to take enough measurements in order to receive a significant mean value.

### How to verify a calibration for tactile measurements?

One checks the calibration by remeasuring the calibration foil on the uncoated sample. It has to be this measuring position, where you measure lateron as well. Fischer Base calibration plates are not useful for this purpose.

### When to use a normalization with a FISCHER X-Ray instrument?

The normalization causes an adjustment of the measurement task for current settings or for new current substrates. This has to be conducted in case of modifications of primary filters or anode currents or collimators. It is also necessary, if alloy compositions or substrates of the sample have changed.

### My FISCHER X-Ray instrument seems to measure implausible values. How can I ensure, that I am measuring correctly?

You should then choose measuring equipment monitoring. You will check the measurement instrument by remeasuring the calibration standards. In case the correct values are not met, adjustments are necessary.

### What does a reference measurement signify, with a FISCHER X-Ray instrument?

A reference measurement is a new calibration of the energy axis. This is relevant for the correction of proportional counter instruments, on the influence of temperature.

### How to check a calibration on the FISCHER X-Ray instrument?

In order to check the calibration, it is necessary to remeasure the calibration standards within the menu position 'Product', 'Measure CAL. standards'. If you find, there is a deviation, then the instrument needs to be recalibrated.

### How often does one need to re-certify FISCHER X-Ray calibration standards?

This is dependant on usage and the customer can determine it by himself.  A typical value would be every 1-3 years.

### Is it possible to stack the X-Ray calibration foils during the calibration?

Yes, it is possible. There is a rough rule for usage: For proportional counter instruments one may use 2-3 foils. For instruments with a PIN/SDD-detector it is possible to use one foil.

### Does one need to re-certify the plate for pure elements, for the FISCHER X-Ray instruments?

This not necessary. You don't need to re-certify the plate, because the elements are saturation thick and therefore very stable.

Kvistgård​/Danmark

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