Calibration
To achieve accurate measurement results, µZ needs to know certain parameters about itself and the environment it's being used in. To determine these parameters, the response of the system needs to be measured in two configurations:
- Short: End cap (with or without microphone, depending on the measurement configuration) mounted directly onto the main tube.
- Long: Calibration tube mounted between the main tube and end cap.
Since µZ is sensitive to changes in climate conditions, the calibration procedure needs to be performed at the start of every measurement session. If the temperature changes by more than 2 °C (3.6 °F) over the session, a new calibration is required. ACME considers a calibration valid if it was performed in the last 12 hours but cannot warn for temperature changes.
The calibration procedure
To calibrate your µZ system, open the Actions menu in ACME's toolbar and click Calibrate µZ system:
This will open the µZ calibration wizard, which will guide you through the entire calibration process. Some additional information about the calibration process is listed below. This information can also be found in the calibration wizard.
Setting speaker output level
To get the best results, the speaker output should be as high as possible, without overloading the microphones. You will get an opportunity to check you levels prior to starting the short calibration measurement. This check is only necessary the first time you calibrate your µZ system.
During the signals check the PPM bars should peak around -15 dB. A speaker output level of -45 dBFS usually works well. If you do find any difficulties, please contact directly.
Two-stage measurements
The calibration measurements are performed using a sweep signal. To maximize the signal quality for each measurement, an amplitude envelope is applied. For this reason, two measurements are performed for each configuration. The initial measurement is used only to calculate the amplitude envelope.
Signal checks
The µZ toolbox performs a number of checks on each measurement to determine whether the system is operating as expected. The checks include:
- Signal levels on the input channels: Are the power supplies of the speaker and all microphones enabled?
- Channel names: Is the data as expected based on the channel name?
- System identification: Is the system that's being calibrated a µZ-20 or µZ-30?
- System configuration check: Is the data compatible with a short or long calibration measurement?
In case any of these checks fail, the calibration wizard will show an error message and give instructions for how the issue can be resolved.
note
If the calibration wizard shows an incorrect error (for example, a mislabeled input channel, while you are certain the channel names are correct) check all your connections and settings and restart the calibration wizard. Also check the signal generator level: if the level is too strong, the microphones may be driven into clipping. If the level is too low, the signal to noise ratio is insufficient for the label checker. If the problem persists, please contact ASCEE.
Saving measurements
Whenever the calibration wizard is closed, either after a successful calibration or after something has gone wrong, you will have the option to save the measurements that were performed so far. In some cases the definitive measurements can be useful for analysis. The initial measurements are generally only useful for debugging purposes.