Desco TB-20686 Installation Manual

TECHNICAL BULLETIN TB-20686

SPI Ground Gard 5 / 5.5
Operation, Installation, and Maintenance

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
ground is needed, and then continuous monitoring
should be considered or even required.” (ESD Handbook
TR 20.20 section 5.3.2.4.4)

SPI-20686

Figure 1. SPI Ground Gard items SPI-20686 and 94391

Description

The SPI-20686 and 94391 are wrist strap and ground

monitoring devices for the electronics work station. It is
designed to constantly monitor two single wire wrist
straps using a Remote Operator Module for each user.

These units provide continuous monitoring of:

• One or two users wearing a wrist strap

• Ground (Verication between electrical and ESD
ground)

Leading companies use continuous monitors as a cost
effective component in satisfying the paragraph 6.1.3
Complicance Verication Plan requirements of ANSI/

ESD S20.20. The SPI-20686 and 94391 Continuous

Monitors provide 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 along with 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-

94391

The SPI-20686 and 94391 will alarm if preset values are

exceeded for capacitance, high resist and ground loss
conditions. The grounding system is redundant and will
still provide a limited grounding even if the utility ground
is lost and the system is in an alarm state.

Capacitance Type Continuous Monitors

“These types of monitors are used with a single wire
(single conductor) wrist strap. Monitors in this category

operate by “sensing” body capacitance. For capaci-

tance 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)

Packaging

Item SPI-20686

1 Ground Gard 5.5 Monitor

2 94340 Remote Operator Modules

2 10 Foot Phone Cords
1 12 Foot Ground Cord
1 Velcro® Set
4 Screws
1 Power Adapter - 3 Prong, 12 Volts

Item 94391

1 Groud Gard 5 Monitor

2 94340 Remote Operator Modules

1 Power Adapter - 2 Prong, 12 Volts
2 Remote Operator Cables
1 Black Ground Cord
1 Green ground Cord
2 Velcro® Strips
4 Screws
1 Certicate of Calibration

Made in America

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

TB-5545 Page 1 of 4 Revision May 2009

TB-20686 September 2010 Page 1 of 4

© 2009 DESCO INDUSTRIES INC.
Employee Owned

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

© 2010 DESCO INDUSTRIES INC.

Employee Owned

Installation

1. SPI-20686 and 94391 Monitor Head:

The SPI-20686 and 94391 Monitors are 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 must be
attached to a facility ground.

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.

Calibration Procedure Using SPI-20780
Tester

Testing the Remote Modules

Refer to Figure 2 to see the connection setup for the

SPI-20780 tester to the SPI-20686 and Figure 3 for the
94391 monitor. Make sure that the switch located on the

face of the tester is toggled to LEFT WS / RIGHT WS. If
connected properly, all three LEDs on the monitor should
be illuminated green.

SPI-20686

Remote

Remote

4. POWER UP TEST

After installing the Monitor , 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. You may also
disconnect the coil cord by unplugging the banana plug
from the Remote Module. Both a 7mm and 4mm Park

Snap is provided on each module.

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 LED for
the left or right wrist strap will light showing the condition
of that strap. If correct, the LED should be GREEN.

SPI-20780

Power Adapter Cord

Figure 2. Connecting the SPI-20686 to the SPI-20780
Tester

94391

Remote

SPI-20780

Remote

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

Power Adapter Cord

momentary break will cause alarms. The remote
modules are set at the factory to allow for sensitivity of

Figure 3. Connecting the 94391 to the SPI-20780 Tester

the “average” human body model.

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

TB-5545 Page 2 of 4 Revision May 2009

TB-20686 Page 2 of 4

© 2009 DESCO INDUSTRIES INC.
Employee Owned

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

© 2010 DESCO INDUSTRIES INC.

Employee Owned