Contec PC-HELPER Series Reference Manual page 54

— —
Function
AI-1204Z-PE Reference Manual
 Start Condition
The condition for controlling the start of sampling can be selected from among software, conversion
data comparison and an external trigger. The conditions for controlling the start and stop of sampling
are completely independent of each other; they can be set separately.
Software
The product starts sampling and storing conversion data to memory immediately after the operation
start command is issued.
Conversion data comparison
When the operation start command is issued, the product compares the analog signal input through
a specified channel to the value of the preset comparison level. If the analog signal satisfies the
condition, the product starts storing input data.
Level comparison conditions are set as two conditions: level and direction.
The above sketch shows that the level comparison condition is satisfied in the rising direction.
The start condition is satisfied when the analog signal at the specified channel passes the comparison
level in the rising direction. Conversion data are stored to memory, starting with those at solid dots.
The above sketch shows that the level comparison condition is satisfied in the falling direction.
The start condition is satisfied when the analog signal at the specified channel passes the comparison
level in the falling direction. Conversion data are stored to memory, starting with those at solid dots.
If you set the level comparison directions to both directions, the start condition is satisfied when the
analog signal passes the level both in the rising and falling directions.
(*)Since this product determines the level comparison with a device driver, sampling starts before
the level comparison condition is satisfied within the system. Therefore, sampling might stop before
the level comparison condition is satisfied due to overflow depending on the conversion speed,
and/or condition of CPU load.
— 54 —