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correctly, the fi rst thing to check is the connection. Look for moisture between
contacts or a loose or broken wire.
Erratic and erroneous readings can also occur due to improper grounding.
See Grounding Issues.
Zero Readings
Continuous zero readings are caused by an open circuit which usually indicates broken
cable, a bad connection, or possibly a damaged sensor. Check the connector to see if a
wire has become loose, or if the cable has been cut. If neither of these appears to cause
the problem, the sensor needs factory repair.
Grounding Issues
It is commonly known that when using electronic equipment, both personnel and equip-
ment need to be protected from high power spikes that may be caused by
lightning, power line surges, or faulty equipment. Without a proper grounding system, a
power spike will fi nd the path of least resistance to earth ground – whether that path is
through sensitive electronic equipment or the person operating the equipment. In order
to ensure safety and prevent equipment damage, a grounding system must be used to
provide a low resistance path to ground.
When using several pieces of interconnected equipment, each of which may have its
own ground, problems with noise, signal interference, and erroneous readings may be
noted. This is caused by a condition known as a Ground Loop. Because of natural re-
sistance in the earth between the grounding points, current can fl ow between the points,
creating an unexpected voltage difference and resulting erroneous readings.
The single most important step in minimizing a ground loop is to tie all equipment
(sensors, dataloggers, external power sources and any other associated equipment) to
a single common grounding point. INW recommends the following: (1) the sensor
cable shield (the wrapped shield inside the cable) be attached to the power ground on
the datalogger and (2) the grounding lug be connected via a 12 AWG or larger wire, to
a grounding rod driven into the earth. It is also recommended that if you are using an
external power supply to power the datalogger that it be tied to the same earth ground.
Notes:
• Proper grounding is very important!
If your sensor does not come with a
connector, INW recommends the following:
(1) the sensor cable shield (the wrapped shield inside the cable) be attached to
the power ground on the datalogger and (2) the grounding lug be connected
via a 12 AWG or larger wire, to a grounding rod driven into the earth. It is
also recommended that your power supply be tied to the same earth ground.
