ESD Systems.com • 432 Northboro Road Central • Marlboro, MA 01752 • (508) 485-7390 • Fax (508) 480-0257 • Website:
ESDSystems.com
Ground Gard 4.5
Operation, Installation, and Maintenance
TECHNICAL BULLETIN TB-5536
Made in the
United States of America
Figure 1. SPI Ground Gard 4.5
Description
The Ground Gard 4.5 is a wrist strap and ground
monitoring device for the electronics work station. It is
designed to constantly monitor two single wire wrist
straps using a Remote Operator Module for each user.
This unit provides continuous monitoring of:
• Two users wearing a wrist strap
• Ground
For a SPI Continuous Monitor that also monitors the
ESD worksurface see SPI model Ground Gard 5.
Leading companies use continuous monitors as a cost
effective component in satisfying the paragraph 6.1.3
Complicance Verification Plan requirements of ANSI/
ESD S20.20. The SPI Ground Gard 4.5 Continuous
Monitor provides continuous monitoring of two operators
and also functions to ensure connection to ground. If the
monitor, using capacitance technology, detects improper
grounding of the operator, the monitor will issue an
audible alarm alongwith an illuminated red LED to notify
the user of a problem.
Many customers are eliminating periodic testing and are
utilizing continuous monitoring to better ensure that their
products were manufactured in an ESD controlled
environment. Continuous monitoring is superior to
periodic testing. “While effective at the time of testing,
wrist strap checker use is periodic. The failure of a wrist
strap between checks may expose products to damage
from electrostatic charge. If the wrist strap system is
checked at the beginning of a shift and subsequently
fails, then an entire shift’s work could be suspect.” (ESD
TR 12-1 Section 1.0 Survey of Constant Monitors for
Wrist Straps)
Continuous Monitors eliminate the need for users to
test wrist straps and log the results; by their function,
these monitors satisfy the ISO 9000 and ANSI/ESD
S20.20 Paragraph 6.2.2.2 test logging requirements.
Per ESD-S1.1 paragraph 6.1.3 Frequency of Functional
Testing “Daily (Wrist Strap) testing may be omitted if
constant monitoring is used.”
“Because wrist straps have a finite life, it is important to
develop a test frequency that will guarantee integrity of
the system. Typical test programs recommend that wrist
straps that are used daily should be tested daily.
However, if the products that are being produced are
of such value that knowledge of a continuous, reliable
ground is needed, and then continuous monitoring
should be considered or even required.” (ESD Handbook
TR 20.20 section 5.3.2.4.4)
The Ground Gard 4.5 is available in two models. The
item numbers are listed below:
94390
94392
ESD Systems.com
• 432 Northboro Road Central • Marlboro, MA 01752 • (508) 485-7390 • Website:
ESDSystems.com
Item Description
94392
Ground Gard 4.5 with Buzzer, 120V
94390
Ground Gard 4.5 with Buzzer, Building Ground, 120V
*Contact manufacturer for quote on 220V models
The Ground Gard 4.5 will alarm if preset values are
exceeded for capacitance, high resistance and ground
loss conditions. The grounding system is redundant
and will still provide limited grounding even if the utility
ground is lost and the system is in an alarm state.
Capacitance Type Continuous Monitors
“This type of monitor is used with a single wire (single
conductor) wrist strap. Monitors in this category operate
by “sensing” body capacitance. For capacitance
monitors, an AC voltage is applied to the wrist strap
through the single conductor ground cord. Due to
capacitive coupling of the person to ground based on the
surroundings, the monitor will indicate either good or bad
depending on the manual adjustment or preset
tolerance. SInce a capacitor or capacitive network
responds like a resistor to an AC current, the single
conductor wrist strap monitor only provides an estimate
of the wrist strap wearer’s apparent resistance.” (ESD
Handbook TR 20.20 section 5.3.9.2 Types of Continuous
Monitors)
TB-5536
August 2018 Page 1 of 3
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