YSI 5200 - Manual (Page 28)

YSI Incorporated 26 5200 Recirculating System Monitor
3.8 Grounding Information
This section contains important installation information regarding grounding of the 5200 Monitor.
Connect earth ground to the 5200 I/O panel as described below in 3.9 Safety ISSUES.
The probe is powered by the 5200 Monitor and will be operated with a “floating” ground reference. This
requires that the probe not be individually grounded. Grounding the probe individually will cause a
“ground loop”; i.e. one conductor of the probe output grounded common to both the probe and the
monitor. Grounding the probe will cause significant performance problems with the sensors and likely
result in erroneous readings.
CAUTION: Do not ground the probe body.
All tanks should be electrically grounded via a ground probe.
3.9 Safety Issues
The electrical system must be grounded via the I/O plate to avoid possible electrical shock or damage to
the equipment (see Figure 3-8 I/O Plate).
WARNING: Turn off all power and assure power “lockout” before servicing to avoid contact with
electrically powered circuits.
To avoid possible electrical shock, do not touch other circuit components when making adjustments to the
5200 Monitor circuit board. Disconnect external power to the unit before connecting or disconnecting
wiring.
3.10 Lightning and Surge Protection
Surge protectors are strongly recommended to protect from secondary surges and lightning on outdoor
installations.
Surge suppression devices should be located on the AC line supplying power to the 5200 Monitor and any
signal lines connecting the 5200 Monitor.
AC line voltage surge suppressors protect field equipment on any AC line to ground from damage due to
electrical transients induced in the interconnecting power lines from lightning discharges and other high
voltage surges. The unit should include noise filtering, common mode and normal mode suppression and
nanosecond reaction time. Surge suppressors should be internally fused to remove the load if the unit is
overloaded or the internal protection fails.
Signal line suppressors protect low voltage signals and relay outputs from damage due to electrical
transients induced in the signal lines from lightning discharges or nearby electrical devices. Signal line
suppressors should be installed at each end of an analog loop. Relay outputs should be protected at the
receiver end. Signal line suppressors should consist of a three-element gas tube followed by metal oxide
varistors and suppressor diodes. The protective elements should be matched such that high-energy surge
voltages trigger the gas surge arrester, while low energy or surge voltages affect the MOV’s and
suppressor diodes.
Lightning protection devices should be located as close to the monitor as possible and wired in
accordance with the National Electric Code in approved watertight enclosures.
CAUTION: This or any other installation procedure cannot protect against a direct lightning strike. YSI
Incorporated cannot accept liability for damage due to lightning or secondary surges.