1.4 Calibration
Acqiris SA240P User's Manual
13
1.4 Calibration
The SA240P is factory calibrated and shipped with a calibration certificate.
The internal calibration refers to the adjustment of ADC card internal parameters, corresponding to
user selected parameters and required before starting acquisition.
Internal calibration
The internal calibration (or self-calibration) measures and adjusts the internal timing, gain and offset
parameters between the ADCs and against a precise reference.
The ADC card includes a high precision voltage source and a 16-bit DAC, used to perform the input
voltage and offset calibration.
The supplied software drivers include self-calibration function which can be executed upon user
request. The ADC cards are never self-calibrated in an automatic way, (i.e. as a consequence of
another operation). This ensures programmers have full control of all calibration operations
performed through software in order to maintain proper event synchronization within automated test
applications.
For accurate time and voltage measurements it is recommended to perform a self-calibration
once the module has attained a stable operating temperature (usually reached after 20 minutes of
ADC card operation after power on).
A full internal calibration of a ADC card can be time consuming because of the many possible
configuration states. Therefore, the self-calibration is performed only for the current configuration
state, and is mandatory before making the first acquisition with given settings. Indeed the AqMD3
driver prevents an acquisition from being performed unless a self-calibration has first been
completed. Note that some configuration changes do not require a new self-calibration. To avoid
unnecessary self-calibrations, the
IAqMD3Calibration.IsRequired
IVI.NET property or the
AQMD3_ATTR_CALIBRATION_IS_REQUIRED
IVI-C attribute should be queried.
ADC card can usually work with signals present at the channel input, or trigger input. However, to
ensure the best performance, or if the calibration is found to be unreliable (as shown by a
calibration failure status), it is recommended to remove such signals.
Similarly, when working with internal clock, it is recommended to remove external reference input
during calibration to avoid parasitic effects.
It is not recommended to perform multiple successive calibrations. If a recurrent calibration failure
occurs, in case of specific application, please contact support for advice.
Switching from one operational modes to another one (e.g. from Averager mode to Zero-
Suppress mode) does not need to recalibrate the card.
