User manual

Programmer’s Guide Page 59 of 64
3.19. Readout of Battery Backed-up Memories
Acqiris digitizers with the battery back-up option permit retaining acquired waveforms during periods of time when
the power might be interrupted.
3.19.1. Preparations before Power-Off
A digitizer only remembers the digitized data array, but not all of the parameters that are needed to interpret the
waveform. These parameters are normally retained in the driver, but are typically lost when power is lost or when the
controlling application is terminated.
It is therefore necessary for the application to transfer the relevant parameters before power-off, typically to a disk,
in such a way that they are again available when restarting the application after power is restored. The following
parameters must be transferred to persistent storage, for each instrument:
• Parameters of AcqrsD1_configHorizontal, i.e. sampling interval and delay
• Parameters of AcqrsD1_configMemory, i.e. number of samples and number of segments
• Parameters of AcqrsD1_configVertical, i.e. Full Scale and offset (the coupling is not relevant!), for each
channel of interest
• Two calibrated delay parameters, as obtained with the function calls
Double delayOffset, delayScale;
Acqrs_getInstrumentInfo(ID, "DelayOffset", &delayOffset);
Acqrs_getInstrumentInfo(ID, "DelayScale", &delayScale);
The functions Acqrs_getInstrumentInfo should be called just before the start of the acquisition, i.e. before calling
AcqrsD1_acquire, but after all AcqrsD1_config… functions.
3.19.2. Recovery after Power-Off
In order to read a battery backed-up waveform, you need to execute a special sequence of initialization functions
1. Initialize the digitizer with the following function call:
Acqrs_InitWithOptions(resourceName, false, false, "CAL=FALSE", &instrID);
It is important to specify “CAL=FALSE” to prevent any calibration in the digitizer, which would destroy any
retained data.
2. Call the functions AcqrsD1_configHorizontal, AcqrsD1_configMemory, AcqrsD1_configVertical (for each
channel!) with the same parameters that were used in the original acquisition.
3. Call the function AcqrsD1_restoreInternalRegisters, with the parameters delayOffset and delayScale. In case
these parameters are not available (e.g. due to earlier software versions), you should use the values –20.0e-9 for
delayOffset and 5.0e-12 for delayScale.
4. Call the function AcqrsD1_readData to read the battery backed-up data.
Failing to restore the originally used digitizer parameters may result in erroneous data. After data recovery, and
before using the digitizer for any new acquisitions, don’t forget to calibrate the instrument with the function
Acqrs_calibrate.
3.20. Reading the Instrument Temperature
The temperature of an instrument can be obtained with the following code:
long temperature; // will be in degrees C
Acqrs_getInstrumentInfo(instrID, "Temperature", &temperature);
When multiple digitizers are combined via AS bus to a MultiInstrument, use the strings "Temperature 0",
"Temperature 1"… to refer to the individual modules.
NOTE: The returned temperature value corresponds to the ambient temperature on the main printed-circuit board,
typically near the timebase circuit. It cannot represent all possible temperature values that are present on the circuit.
Values
≥ 60
o
C indicate that the circuit is near its operational limit, and a cooling failure occurred or better cooling
should be installed.
We recommend keeping the temperature as low as possible, since a 10
o
C reduction in circuit temperature is expected
to improve the mean-time-between-failures (MTBF) by a factor of 2.