Use of pulldown resistor in cnReach IO module

The cnReach IO module provides 4 strong pulldown resistors. They are available in channel 0 through channel 3. Note that all eight channels provides 8 weak pulldown resistors (65kohm) by default. The strong pulldown resistors have low impedence of 250ohm. These strong pulldown resistors can be enabled on channel 0 through channel 3. When the cnReach IO module is used for analog input based on input current mAm, the strong pulldown resistor needs to be enabled. This will allow the input current to flow through so the current can be measured by the cnReach input pin. One can use Modbus Poll the read in the current mAm value. For example, a pressure sensor can translate pressure value in to different level of current. The current will flow through the cnReach IO pin. The Modbus Poll will reach the crrent value from the pin. A controller application can interpret this mAm value into pressure value and take actions, for example to shutdown a pump is the pressure level reaches certain point, etc.

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