Terminal Master; Ground Loops; Common Causes - Campbell CR300 Series Product Manual

22.9.3 Terminal master

Use the Terminal master command from a terminal mode to manually interrogate and enter
settings in smart-sensors connected to a remote CR300 series. The Terminal master is useful for
remotely accessing data logger terminal features such as SDI-12 and serial talk through modes
for configuration and trouble shooting.
Using a terminal emulator enter the CR300 series terminal mode. For more information, see
Using terminal mode (p. 179)
1. Press Enter until the data logger responds with the prompt CR300 series>.
2. Type T at the prompt and press Enter.
3. In response, select the PakBus address of the remote data logger.
Once the Terminal master option is entered, the terminal will present a new prompt,
n*CR300>, where n is the remote CR300 series PakBus address.
4. Now, the remote device terminal functions can be accessed.

22.10 Ground loops

A ground loop is a condition in an electrical system that contains multiple conductive paths for
the flow of electrical current between two nodes. Multiple paths are usually associated with the
ground or 0 V-potential point of the circuit. Ground loops can result in signal noise,
communications errors, or a damaging flow of ground current on long cables. Most often,
ground loops do not have drastic negative effects and may be unavoidable. Special cases exist
where additional grounding helps shield noise from sensitive signals; however, in these cases,
multiple ground conductors are usually run tightly in parallel without conductive shielding
material placed between the parallel grounds. If possible, ground loops should be avoided.
When problems arise in a system, ground loops may be the source of the problems.
See also Grounds (p. 13).

22.10.1 Common causes

Some of the common causes of ground loops include the following:
The drain wire of a shielded cable is connected to the local ground at both ends, and the
l
ground is already being carried by a conductor inside the cable. In this case, two wires, one
on either side of the cable shield, are connected to the ground nodes at both ends of the
22. Tips and troubleshooting 184