Desco TB-3050 Installation Manual

TECHNICAL BULLETIN TB-3050

Jewel® Workstation Continuous Mini Monitor
Operation, Installation and Maintenance

A broken wrist strap may expose products to ESD
over an entire shift if it is checked only at shift change
with wrist strap checker.” (ESD TR 12-01 Section 4.2
Selection Considerations)

The Jewel® Workstation Continuous Monitor eliminates
the need for periodic wrist strap tests and logging.
Continuous monitoring is superior to periodic or pulsed
testing, and can save a signicant amount of money
in testing costs and rejected product. Periodic testing
detects failures after ESD susceptible products way
have been manufactured. The costs of dealing with
the resulting catastrophic or latent defects can be
considerable. Jewel® Workstation Continuous Mini

Figure 1. Desco 19218 Jewel® Workstation Continuous
Mini Monitor

Description

The Jewel® Workstation Continuous Mini Monitor
independently monitors the operator and the
worksurface. The instant an operator’s wrist strap or
cord fails, the monitor will issue audible and visual
alarms alerting the user of the problem. In the same
manner, the unit also conrms that a path to ground
of less than 500 megohms exists from the ESD
worksurface.

The Jewel® Workstation Continuous Monitor is a Single
Conductor Impedance Sensing Continuous Monitor
which per ESD Handbook TR20.20 section 5.3.9.2.1 “a
small AC voltage is used in a detection circuit designed
to eliminate false alarms and adjustment. They use the
phase difference between current and voltage to detect
changes in impedance of the grounding cord, wristband
and person. No adjustments are required.”

Per ESD Handbook ESD TR20.20 section 5.3.2.4.4,
“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 monioring should be considered or
even required.”

Advantages Of Continuous Monitoring
Over Periodic Testing

“When considering constant [or continuous] monitors,
the equipment cost including the wrist strap,
maintenance and training cost, labor time for performing
wrist strap tests, and the potential failures due to non­functional wrist straps should be considered.

Monitors eliminate the need for operaters to test wrist
straps and log the results; by their function, these
monitors satisfy the ISO 9000 and ANSI/ESD S20.20
test logging. ANSI/ESD S20.20 Section 6.2.2.2
Personnel Grounding Guidance states “A log should be
maintained which veries that personnel have tested
their personal grounding devices.” Per ANSI/ESD-S1.1
Annex A Section 6.1.3 “Daily (wrist strap system) testing
may be omitted if constant monitoring is used.” Per
ANSI/ESD-S1.1 Annex A Frequency of Functional
Testing, “The wrist strap system should be tested daily
to ensure proper electrical value. Daily testing may be
omitted if constant monitoring is used.”

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
wrist cord storage (visual red LED will illuminate). When
the operator touches the Park Snap, the audible alarm
is disabled for about 8-10 seconds. The operator can
remove the wrist strap cord and attach socket of the
cord to Park Snap for storage. The coil cord may also
be removed from the jack on the Jewel® monitor without
the alarm sounding. Once the coil cord is in the park
position, the operator ground status light will remain red.

Wave Distortion Detection Technology
Provides True 100% Continuous Monitoring

Wave distortion impedance circuitry monitors current /
voltage phase shifts and provides true 100% continuous
monitoring. Electrical current will lead voltage at various
points due to the combinations of resistance and
capacitive reactance. By monitoring these “distortions”
or phase shifts, the Jewel® Workstation Continuous Mini
Monitor will reliably determine if the circuit is complete.

Made in America

TB-3050 Page 1 of 4

DESCO EAST - One Colgate Way, Canton, MA 02021-1407 • [phone] • Fax [phone] • Website: Desco.com

DESCO WEST - 3651 Walnut Avenue, Chino, CA 91710 • [phone] • Fax [phone]

January 2011

© 2011 DESCO INDUSTRIES, INC.

Employee Owned

Wave distortion technology can be referred to as “vector
impedance monitoring”. This description is valid as the
wave distortion technology measures the impedance
at the monitored banana jack and looks for changes in
either the capacitance or resistance of the circuit which
includes the wrist strap and its wearer. It uses ltering
and time domain sampling to lter out false signals
caused by voltage offsets, 60 Hz elds and other electro­magnetic and electrostatic interference.

In normal factory environments, and with persons whose
capacitance with respect to ground is within design limits
(5 feet tall 90 pound person to 6 foot 5 inch 250 pound
person), the Jewel® Workstation Continuous Mini Monitor
cannot be “fooled”. It will provide a reliable alarm only
when the wrist strap or work surface becomes
dysfunctional or unsafe according to accepted industry
standards. The Jewel® Workstation Continuous Mini
Monitor is drift-free and designed to be insensitive to the
effects of squeezing or stretching the coil cord.

Advantages Of Wave Distortion And Single­Wire Technology

The Jewel® Workstation Continuous Mini Monitor
allows the use of any standard, single-wire wrist strap
and coil cord. The monitor / wrist strap / cord system
life-cycle costs are by far lower than alternative systems
which require expensive and less durable dual-wire
cords and special wrist straps. The Jewel® Workstation
Continuous Mini Monitor is an economical way to
monitor both the operator’s wrist strap and workstation
surface. See “Maintenance and Calibration” (page 4) to
minimize life-cycle costs.

The dictionary denes constant as uniform and
unchanging, and continuous as uninterrupted.
Nonetheless, some dual-wire resistance monitors utilize
a pulsed test current and do not provide continuous
monitoring. For example, during each 2.2 second pulse
cycle of a leading “constant” resistive monitor, electrical
current is pulsed for only 0.2 seconds followed by an
unmonitored interval of 2 seconds. This leaves the user
/ wrist strap unmonitored for over 90% of each cycle.
Damaging static charges can easily occur in the portion
of the time in between the pulses. The off period of 2
seconds equals 2 billion nanoseconds, and “it takes
only about 25 volts applied for 100 nanoseconds to blow
most memories or microprocessors”.*

Worksurface Channel

The Jewel® Workstation Continuous Mini Monitor
monitoring circuitry is sufciently sensitive to detect
extremely low current, allowing it to be used with mats
having a resistance of up to 5 x 10E8 ohms RTG. When
the Monitor is connected to an ESD Mat worksurface,
the amount of current that ows is a function of the
total resistance between the monitor and through the
worksurface to ground. When the resistance of the
worksurface is below a pre-set threshold, the monitor
will indicate good. Conversely, if the resistance level is
high when compared to the monitor’s reference, the unit
will alarm. This is an integrating resistance measuring
circuit, therefore it is relatively insensitive to externally
induced electromagnetic elds. The resistance threshold
is factory set to 500 megohms. (It can be special
ordered to other limits. Limits can be varied and set to 1
gigohm maximum.)

Packaging

1 Jewel® Workstation Continuous Mini Monitor
2 Push and Clinch Snaps
1 Power Adapter, 24VAC, N. America
1 Certicate of Calibration

Installation

Conrm that the surface resistance (RTG) of the mat is
5 x 10E8 ohms or less and has a conductive layer. We

recommend the Desco 19780 or 19635 Tester. Remove

the monitor from its packaging and inspect for any
shipping damage.

The Continuous Mini Monitor is normally installed toward
the front edge of a workstation where the LEDs are
easily visible. The unit is designed to be snapped on the
worksurface using the 10mm snap studs mounted at the
bottom of the monitor (see Figure 2).

ESD MAT

Push and Clinch Snaps

By using the reliable wave distortion impedance
technology to determine if the circuit is complete, there
are no false alarms. There is no need to adjust or
tune the monitor to a specic user or installation. The
miniscule amount of electrical current (less than 1 volt
coil cord signal) required to generate the waveform has
never caused reported skin irritation and is extremely
safe for use in voltage sensitive applications such as
disk drive manufacturing.

DESCO WEST - 3651 Walnut Avenue, Chino, CA 91710 • [phone] • Fax [phone]

DESCO EAST - One Colgate Way, Canton, MA 02021-1407 • [phone] • Fax [phone] • Website: Desco.com

TB-3050 Page 2 of 4

1-5/16"

Figure 2. Installation of push and clinch snaps to
worksurface

© 2011 DESCO INDUSTRIES, INC.

Employee Owned