User manual

Programmer’s Guide Page 27 of 66
3.4.4. Configuring Noise Suppressed Accumulation (NSA)
As discussed in the User Manual Family of Averagers the module can be configured to only accept data above a
fixed threshold and, if desired, to shift the data in that case. Since these two values are expressed in Volts and used as
ADC counts they have to be converted before use. The User Manual describes this transformation that depends on
whether Data Inversion has been enabled. The NSA threshold functionality must be enabled and a threshold defined.
If this has been done the NSA base subtraction can also be enabled and will be activated using the defined base
value. The order of the calls to AcqrsD1_configAvgConfig is not important since the final decision is taken when the
acquisition is started. However, the correct full scale should be selected with AcqrsD1_configVertical before setting
the NSA levels. Here is an example:
const long channelNbr = 0;
double fsr, offset, threshold, base;
threshold = - offset; // place the threshold at the middle of the screen
base = threshold - fsr/10.; // place the base one division below the
threshold
// set the base and threshold voltage values
AcqrsD1_configAvgConfig(instrID, channelNbr, "Threshold", &threshold);
AcqrsD1_configAvgConfig(instrID, channelNbr, "NoiseBase", &base);
// enable the NSA functionality
AcqrsD1_configAvgConfig(instrID, channelNbr, "ThresholdEnable",1);
AcqrsD1_configAvgConfig(instrID, channelNbr, "NoiseBaseEnable",1);
3.5. Configuring SSR Analyzers
3.5.1. Acquisition Parameters
The AP235/AP240 SSR analyzers have 2 operational modes, normal and SSR, controlled with the function:
AcqrsD1_configMode(instrID, mode, 0, 0);
The value mode can be set to 0 (normal) or 7 (SSR mode).
The SSR mode requires a number of additional configuration parameters that describe the requested acquisition and
readout conditions.
Use the following short code fragment to configure a buffered acquisition sequence of 800 waveforms of 5000 data
points, with a start delay of 128 samples:
// Common Configure
long nbrSamples = 5000, nbrSegments = 800;
long startDelay = 128, stopDelay = 0;
AcqrsD1_configMode(instrID, 7, 0, 0);
AcqrsD1_configAvgConfig(instrID, 0, "NbrSamples", &nbrSamples);
AcqrsD1_configAvgConfig(instrID, 0, "NbrSegments", &nbrSegments);
AcqrsD1_configAvgConfig(instrID, 0, "StartDelay", &startDelay);
AcqrsD1_configAvgConfig(instrID, 0, "StopDelay", &stopDelay);
Comments:
The value of the third and fourth arguments to AcqrsD1_configMode must always be 0.
When in SSR mode, the following digitizer parameters are ignored:
delayTime of the function AcqrsD1_configHorizontal is replaced by “StartDelay” and “StopDelay”
nbrSamples and nbrSegments of the function AcqrsD1_configMemory are replaced by “NbrSamples”
and “NbrSegments” in the function AcqrsD1_configAvgConfig.
The values nbrSamples, startDelay and stopDelay must be integer multiples of the „block size‟, which is
always 16 in the AP240/AP235 Dual-channel mode, and 32 AP240/AP235 Single-channel mode. If the
supplied value is not an integer multiple of the „averaging block size‟, it is truncated to the next lower