Aim MIL-STD-1553 - Apicmdscopeoffsetcompensation

MIL-STD-1553 Reference Manual
406
Chapter 9 – Bus Monitor Functions
9.1.41 ApiCmdScopeOffsetCompensation
Prototype:
AiInt16 ApiCmdScopeOffsetCompensation(AiUInt32 ulModuleHandle, AiUInt8 ucMode,
TY_API_SCOPE_OFFSETS* pxOffsets );
Driver Command:
NONE
Purpose:
Like on a normal Osziloscope, where the probes are connected to GND to find the zero-line,
this function is used to find and set the zero-line for the MIL-Scope. Use this function each
time before a precise measurement should be started, for compensation of el. components
tolerances and temperature drifts.
It will perform some measurement probes to determine the pitch of the scope data from the
zero line of an idle bus.
An offset from the sampled values will be determined by calculating the mean value of the
noise and DC drift on the idle bus in each of the available scope modes. For all further scope
recordings, the ascertained offsets will be used to do an automated correction of the scope
sample values.
Note: This function is only usable with AIM’s APE MIL-Scope module.
Note: The hardware needs to be set into a defined state before this function to
determine the offset compensation is run.
The coupling of channel A and B must NOT be set to internal. If you’re using
API_CAL_CPL_ISOLATED as coupling mode, please call function
ApiCmdCalCplCon in order to set any of the other possible coupling modes.
It is also not allowed to have any BC or RT simulation running during the
measurement process and the bus must be idle.
The zero line pitch is temperature dependent. Deviations of about 500mV can
be observed in a temperature range from -40 to 80°C. So it is recommended
to re-adjust the zero line from time to time, or if it is necessary to make sure
to have the max. accuracy.
The offset values for the “API_SCOPE_COUPLING_EXTERN” modes are
adopted from the measured values of the “API_SCOPE_COUPLING_STUB”
modes instead of being calculated separately.