How to connect RS232 signal ground?

Question

Electronics

Good afternoon. I have a sensor that needs to be connected to a data logger via the RS232 interface. The sensor is powered directly through the datalogger's DB9 connector. Thus, there is no space left to connect the signal ground of the sensor. According to the pinout, the data logger does not have a separate signal ground at all, only a power ground. I connected the signal ground and the power ground together in the hope that this is how it should work, but alas, the data logger shows that there is no data from the sensor. Although the sensor itself is in good order and connects to the computer via a USB-RS232 adapter without any problems (in this case, the sensor is powered separately, and only RX, TX and SGND are connected to the adapter).

I do not think that the problem is in the data logger, after all, the device is very serious and new.

Answer 1

Try to throw on the connector housing. He is connected to the earth.

Answer 2

And what prevents you from connecting the power as separately as in the case of a PC?
but in general, as I understand it, you need to unsolder the chip for the logger - with contacts 2,3,5, 9 (is this power?)
and towards the sensor: (3,2) - cross rx and tx, 5 - ground, 9 power . Signal ground and power ground will be common.

Answer 3

In this situation, it probably makes no sense to try to disconnect the signal ground from the power ground.