Basic questions about the pins of a wire

[Henol]

Hello everyone,

First of all, I'm sorry for any mistake I may make, I'm not English.
I've also never worked in electronics.

Here is my situation: I've been told to power a particular device and to transmit its signal to a BNC, without any more information. After some research, I found that I'm gonna have to deal with a 9pin cable. I found two diagrams of this cable:

Firt diagram:
Shield
Pwr Rtn
Power-
Pwr Rtn
Power+
Lock-
Lock+
Sig -
Sig +

Second diagram:
Shield
Gnd
Power-
Gnd
Power+
Gnd
Press+
Sig -
Sig +


Here are a few questions, but feel free to give any advice for newbe:

1) Shield, Power Rtn (Return?), Lock-, and ground all have to be grounded, have they not? Why are they called differently ?

2) How to transmit the signal to a BNC ?
Sig- for the outside of the BNC, Sig + for the inside ? Or should I ground the outside and transmit only sig+ to the inside, and don't use sig- ?

3) What's Press+/Lock+ ? What do I have to do with that ?

I will perhaps think about other questions later;

Thank you for your help!!

 

[MikeMl]

Without knowing what the device is, we are only guessing. For example, the Sig+/Sig- terminology probably means a balanced, differential signaling method, where both wires are isolated from "gnd".

Why would you put BNC connectors on the individual wires when this cries out for a DB-9?

 

[Henol]

Hello,

Thks for your answer;

The device is a seismometer;

Sorry I was not clear: I will in fact have a cable that exactly looks like the DB-9. It will be connected at one end to the device but I'm actually creating the box that will be connected to the other end.
This box needs to supply power and it will also allow to see the signal with a BNC cable.
BNC is chosen in order to see the signal on a scope.

Let me know if you have any other question.

For the Sig+/Sig-, does it correspond to the two wires of a BNC ? Sig- outside ?

 

[MikeMl]

...

For the Sig+/Sig-, does it correspond to the two wires of a BNC ? Sig- outside ?

No. If the signaling is balanced differential (Like RS485), then you need three connections: Sig+, Sig- and the ground reference. You will need a differential scope with a differential vertical input (or use two scope channels A & B set to the same gain and then display A-B). Two BNCs side-by-side would do it.

 

[crutschow]

If you want to view a differential signal with just a single input of a scope, you could add a differential instrumentation amp to convert the differential signal to single-ended.