ESD 94390, 94392 Operation, Installation, And Maintenance Manual

TECHNICAL BULLETIN TB-5536

Ground Gard 4.5
Operation, Installation, and Maintenance

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 nite 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

94390

Figure 1. SPI Ground Gard 4.5

94392

ground is needed, and then continuous monitoring

should be considered or even required.” (ESD Handbook
TR 20.20 section 5.3.2.4.4)

Made in the

United States of America

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

e󰀨ective component in satisfying the paragraph 6.1.3
Complicance Verication 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 e󰀨ective 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)

The Ground Gard 4.5 is available in two models. The
item numbers are listed below:

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)

ESD Systems.com • 432 Northboro Road Central • Marlboro, MA 01752 • [phone] • Website: ESDSystems.com

ESD Systems.com • 432 Northboro Road Central • Marlboro, MA 01752 • [phone] • Fax [phone] • Website: ESDSystems.com

TB-5536 August 2018 Page 1 of 3

© 2018 DESCO INDUSTRIES INC

Employee Owned

Packaging

1 Ground Gard 4.5 Monitor

2 94340 Operator Remotes

1 Operator Remote Cables, 10 ft.
1 Monitor Ground Cord, 12 ft. (94390 only)
1 Hook and Loop Fastener Strip
1 12VDC Power Adapter, North America
1 Certicate of Calibration

Remote Module Description

Inside both remote modules are infrared sensors that
react to the insertion of a wrist strap wire with a banana
plug. When the banana plug is inserted, the base unit is
activated for that remote module. The Monitor Head LED
for the left or right wrist strap will light showing the
condition of that strap. If correct, the LED should be

GREEN.

Installation

1. GROUND GARD 4.5 Monitor Head:

The Ground Gard 4.5 Monitor Head is designed to
maximize valuable work area and should be mounted at
eye level above the workstation, either on a post or shelf

support. A double-sided adhesive Velcro® attachment is

provided to hold the lightweight head in place.

2. GROUND CONNECTION:

The green wire extending from the monitor head (item

94390) must be attached to equipment ground. This wire

can be connected directly or looped through the
conductive table top or mat to ground. There is no green
wire on item 94392. For this item, the ground connection

is made through the third prong of the 3-wire Power

Adapter.

Caution: The total amount of resistance through all

monitored parts should not exceed 10.0 megohms

total.

3. REMOTE OPERATOR MODULES:

The remote operator modules can be
mounted at the front of the work
surface, usually under the tabletop and

ush with the front edge. Two screws for each unit are

provided for mounting. Connect each remote to the

monitor unit using the telephone cable with RJ11

connectors.

4. POWER UP TEST

After installing the Monitor Head, remote units, and
making the necessary connections without the wrist

straps connected, the unit should POWER UP with the
wrist strap LED’s OFF and the audible alarm SILENT.

If you have no response to power or a red LED, check
AC outlet for proper ground or refer to trouble shooting
section.

PARK SNAP

The audible alarm is designed to alert both operator and

supervisor. The Park Snap feature provides a means

for an operator to disconnect when normally leaving
the work area, without the audible alarm sounding, and
it provides a means of wrist cord storage (visual red
LED will illuminate). You may also disconnect coil cord
by unplugging banana plug from the Remote Operator

Module. Both a 7mm and 4mm Park Snap is provided on

each module.

Should the wrist strap fail, be worn incorrectly or

removed by the operator, the red indicator will ash,

calling attention to a problem. Should the ground
connection be lost, the red light and alarm will be
activated The monitors are continuous and even
a momentary break will cause alarms. The remote
modules are set at the factory to allow for sensitivity of
the “average” human body model.

Calibration Procedure Using 94335
Tester

With coiled wires connected to test unit and each remote,
observe the following: both lights should illuminate green
on the head module, with no buttons depressed on the

tester. Pressing buttons one or four should cause the left

or right wrist strap to go red simulating a high resistance
condition on the wrist strap. This shows that the Remote
Operator Module is properly calibrated.

If the above conditions are not met, complete the
following adjustment:

With buttons one and four not depressed, the LED
display on the head module should be in a green

condition. If not, nd the adjusting port on the remote.

Inside there is an adjusting trim pot. Turn the trim pot
slightly until the head module LED turns green.

Step One: Turn the pot until the green LED triggers red,
then ease back until LED triggers green.

Step Two: Press the corresponding button on the test

unit and the LED will go red on the head module. This
shows the Ground Gard remote is in a proper calibration.

Note: If the unit does not go red, go back to step one
and repeat procedure.

Installation Adjustments

Should your system alarm without obvious cause, rst

troubleshoot and verify all connections. If all the
connections are correct, the base unit should be

adjusted to compensate for a di󰀨erent HBM (human
body model). We preset the units at the factory at 100pF

and your operator might be out of the tolerance range
caused either by body chemistry, bulk capacitance or

impedance di󰀨erences.

Follow these steps to adjust and personalize the base

unit:

ESD Systems.com • 432 Northboro Road Central • Marlboro, MA 01752 • [phone] • Website: ESDSystems.com

ESD Systems.com • 432 Northboro Road Central • Marlboro, MA 01752 • [phone] • Fax [phone] • Website: ESDSystems.com

TB-5536 Page 2 of 3

© 2018 DESCO INDUSTRIES INC

Employee Owned