A: To verify the operational status of the S terminal (multifunctional input terminal), the following methods may be employed:

Measure terminal voltage
Using a multimeter set to the DC voltage range, measure the voltage between the S terminal under test (e.g., S1) and the COM-1 terminal:
·   Normal state: When an external contact closes to activate the S terminal, the voltage should be approximately 24V; when the terminal is open-circuited or the contact is broken, the voltage should be 0V.

Check digital input functionality
This is the most direct method. Apply a valid switch signal to the S terminal and observe the system response:
1.  Configure the S terminal under test to a specific function (e.g., ‘Run Signal’ or ‘Fault Reset’) via function codes (e.g., P05.00-P05.11).
2.  Close the external contact corresponding to that S terminal.
3.  Observe whether the VFD or iSVG system executes the set function (e.g., starts or resets a fault). A normal response indicates the S terminal function is operational.

Observing Indicator Light Status
Some equipment control boards may feature indicator lights corresponding to digital input states. When the S terminal is active, the relevant indicator light should illuminate, aiding verification that the terminal has correctly received the signal.

Precautions
·   The S terminal input voltage must utilise the system's built-in 24V power supply; external power sources must not be connected.
·   An unconnected terminal is interpreted by the system as being in a disconnected state.
·   Should significant on-site interference occur, appropriately increase the value of function code P05.13 (Digital Input Filter Frequency) to prevent false triggering.

By following the above steps, you can effectively verify the operational status of the S terminal. Should the function test fail to respond or voltage measurements prove abnormal, it may be necessary to inspect external wiring, terminal connections, or the control board itself.