Campbell Scientific CR23X Micrologger - Manual (Page 233)

SECTION 14. INSTALLATION AND MAINTENANCE
14-7
CR23X
Panel
+12V
G
FIGURE 14.6-2. Connecting to Vehicle Power Supply
14.7 CR23X Grounding
Grounding of the CR23X and its peripheral
devices and sensors is critical in all
applications. Proper grounding will ensure the
maximum ESD (electrostatic discharge)
protection and the higher measurement
accuracy.
14.7.1 ESD PROTECTION
An ESD (electrostatic discharge) can originate
from several sources. However, the most
common, and by far potentially the most
destructive, are primary and secondary lightning
strikes. Primary lightning strikes hit the
datalogger or sensors directly. Secondary
strikes induce a voltage in power lines or sensor
wires.
The primary devices for protection against ESD
are gas-discharge tubes (GDT). All critical
inputs and outputs on the CR23X are protected
with GDTs (RS-232, CS I/O and 12 Vin do not
have GDTs). The GDTs fire at 150 V to allow
current to be diverted to the earth ground lug.
To be effective, the earth ground lug must be
properly connected to earth (chassis) ground.
As shown in Figure 14.7-1, the power ground
and signal ground are independent lines until
joined inside the CR23X.