Avoiding measurement errors

A/D converters with a higher resolution are very precise measuring instruments that can detect even the smallest changes in the measurement signal. In practice, electrical or electromagnetic interference often affects the measurement signal via the connecting cable and distorts it. The measurement signals can be smoothed and optimized with the help of an A/D filter.

Solution

The software-based filter we use has already been integrated into the microcontroller, which controls the A/D converter. Various filter levels can be set and read back via software commands.
The filter principle is based on averaging a sum of measurements. The higher the filter level is selected, the more measurements are used to calculate the average value. However, this also means that the sampling rate of the A/D converter is reduced as the filter level increases.

Application

Each time the module is restarted, the A/D filter is initially switched off and can be activated using the DELIB command if required. It is therefore advisable to set the A/D filter in the initialization of your project. The maximum number of filter levels that can be set can vary depending on the product. To determine the maximum A/D filter that can be set, the filter level can be set to 250. When reading back the filter, you will now receive the maximum value.
The following commands can be used to set the A/D filter:

• DapiSpecialCommand(handle, DAPI_SPECIAL_CMD_AD, DAPI_SPECIAL_AD_FILTER_SET, ((filterlevel & 0xff) << 8) | (submodule_nr & 0xff) , 0)
• DapiSpecialCommand(handle, DAPI_SPECIAL_CMD_AD, DAPI_SPECIAL_AD_FILTER_GET, (submodule_nr & 0xff) , 0)

Further examples can be found in the manual for your module in the section:A/D converter functions