connecting grove sensors directly to an arduino


i recently bought grove piezo sensor and grove GSR sensor and i want to connect them directly to an arduino (without using base shield).
in the GSR sensor there are 4 connection: GND,VCC,TP4,SIG. does anyone knows where to connect the TP4 in the arduino?
i googled it and saw in an arduino forum that i dont have to connect TP4 to anything but there must be a reason why it exist.
the same question i have with the piezo sensor only the piezo sensor has NC connection instead of the TP4 in the GSR sensor.



The NC means no connection in both the cases of GSR and Piezo sensors.The Grove connectors has 4 pins.It is just an extra pin to connect with the base shield.Connect the VCC,GND and SIG pins to their respective pins in the Arduino.
That’s enough for the functioning of these sensor.


You can observe that this pin is wired directly to one of the skin sensor probes. It is connected, thus, it’s NOT the same as the “NC” on other boards (obviously - it’s labelled TP4, not NC, after all).

Please find the attached image.Its mentioned NC in the new version.
grove gsr.png