# Calibration Definitions

### Absorption

This is understood to mean the penetration of gases or gas mixtures into liquids or solid substances. NO2, for instance, is absorbed/fixed by rubber or silicone hoses.

### Adsorption

Adsortpion takes place if gases are held solely by the surface forces when they come into contact with a solid substance, e.g. the inside wall of a hose. These "captured gases are then given off again uncrolledly (e.g. the presence of NO2 ls indicated even though no more NO2 gas is applied).

### Calibration Adjustment or Span

To adjust the measured reading to the smallest possible deviation according to the known standard value or reference (i.e. for analyzer calibration gas). Therefore, adjustment requires a change of the instrument settings.

### Calibration Check

Comparison of an analyzer's output signal (measured reading) to a known standard.

### Cross-Sensitivity

The characteristic of sensors to react not only to the target gas to be verified, but also to other gases.

### Error or Measurement (Accuracy)

Indicated measurement minus the true value of the measured variable. This can be represented in a variety of ways:

• Relative deviation from the measured value
• Deviation relative to the limit value of the measuring range
• Absolute indication, for instance as vol.% or ppm

### Linearity

Deviation from the correct values of the measured values displayed across a measuring range.

### Measuring Range

This is the concentration range in which the target gas can be measured by the sensor/unit with the specified accuracy.

### Oxidation

The combination of elements with oxygen. In gases, for instance, the oxidation of NO produces NO2.

### Reproducibility (Repeat Accuracy)

Standard deviation of a series of measured values from measurements performed at short intervals of time and carried out according to a defined measurement procedure by the same operator on the same parts, using the same equipment and at the same place.

### Response Time

Period of time the sensor/unit needs in order to react to the introduced concentration with a stable signal/indication. In practice, txy times are given, e.g. T90 time. This is the length of time until 90% of the introduced concentration is displayed.

### Zero Point

What the sensor signal unit displays in the absence of the gas to be verified (="target gas").