Desco 19246 Installation Manual

TECHNICAL BULLETIN TB-3058

Dual Operator Workstation Continuous Monitor with
Satellites - Operation, Installation and Maintenance

No user adjustment required: The Continuous Monitor

is drift-free and designed to be insensitive to the effects of
squeezing or stretching the coil cord. It requires no user
adjustment.

The Dual Operator Workstation Continuous Monitor is a
real time instrument that ensures that critical ESD control
components in a sensitive area are effectively grounded. It
independently monitors the operator and the work surface.
The instant an operators 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 confirms that a
path to ground of less than 10 megohms (1 x 10E7 ohms)
exists from the ESD protective work surface(s).

ADVANTAGES OF CONTINUOUS MONITORING

Figure 1. Desco Dual Operator Continuous Monitor with
Satellites

Description

Leading companies use continuous monitors as a cost effective
component in satisfying the paragraph 6.1.3 Compliance
Verification Plan requirements of ANSI/ESD S20.20. The
Desco Dual Operator Continuous Monitor with Satellites
continuously monitors the grounding integrity of two operators,
and two ESD worksurfaces’ path to ground. The monitor will
provide instantaneous notification of static control equipment
failures, and eliminates the need of costly and difficult to
supervise wrist strap logging record keeping. This unit is highly
cost effective as it is designed to monitor any conventional
single-wire wrist strap and ground cord system.

Per ESD Handbook TR 20.20 paragraph 5.3.2.4.4 Test
Frequency, “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, then continuous monitoring should be considered or
even required.”

The Dual Operator Continuous Monitor with Satellites is
available in two models.

Model Voltage AC

19246 120 Volt

19247 220 Volt

OVER PERIODIC TESTING

Many customers are eliminating periodic touch testing of wrist
straps and are utilizing continuous monitoring to better ensure
that their products were manufactured in an ESD protected
environment. Full time continuous monitoring is superior to
periodic or pulsed testing, and can save a significant amount
of money in testing costs and rejected product. Periodic testing
detects wrist strap failures after ESD susceptible products have
been manufactured. The costs of dealing with the resulting
catastrophic failures or latent defects can be considerable.
Dual Operator Workstation Continuous Monitors eliminate the
need for users to test wrist straps and log the results; by their
function, these monitors satisfy the ISO and ANSI/ESD S20.20
test logging. ANSI/ESD S20.20 Paragraph 6.2.2.2 Personnel
Grounding Guidance states “A log should be maintained which
verifies that personnel have tested their personal grounding
devices.” Per ESD-S1.1 Paragraph 6.1.3 “Daily (wrist strap
system) testing may be omitted if constant monitoring is used.”

WAVE DISTORTION DETECTION TECHNOLOGY
PROVIDES TRUE 100% CONTINUOUS MONITORING

From the technical alternatives available, Desco designs
and manufactures many of its Continuous Monitor product
offerings using wave distortion technology . Wave distortion
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 wave distortion Workstation Continuous
Monitor will reliably determine if the circuit is complete.

Made in the

United States of America

19248 Satellite Remote Monitor

The Dual Operator Continuous Monitor with Satellites is an
impedance sensing device designed to monitor body types
from a 5th percentile female to a 95th percentile male. This
range covers a 5 foot tall 90 pound person to a 6 foot 5 inch
250 pound person in any production environment.* The 19246
is powered by a 120 VAC, 60/50 Hz, plug-in transformer which
also provides connection to ground.

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-3058 November 2011 Page 1 of 4

*NASA Publication 1024-Anthropomorphic Source Book Volume 1:
“Anthropometry for Designers”

** Per ANSI/ESD S20.20 paragraph 6.0.3. Tailoring “This
document, or portions thereof, may not apply to all applica tions.
Tailoring is accomplished by evaluating the applicability of each
requirement for the specific application. Upon completion of the
evaluation, requirements may be added, modified or deleted.
Tailoring decisions, including rationale, shall be documented in the
ESD Control Program Plan.”

© 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 filtering and time domain sampling
to filter out false signals caused by voltage offsets, 60 Hz fields
and other electro-magnetic 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 Dual Operator Workstation Continuous 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 Dual Operator
Workstation Continuous Monitor is drift-free and designed to
be insensitive to the effects of squeezing or stretching the coil
cord.

ADVANTAGES OF WAVE DISTORTION AND SINGLE-WIRE
TECHNOLOGY

The Desco Dual Operator Workstation Continuous 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 more
expensive & less durable dual-wire cords and special wrist
straps. Dual-wire cords are expensive and are the weak
link of the system. They are the most likely component to
need replacement. Over a five year period this can make
a dual-wire system three times as expensive as a system
utilizing single-wire wrist straps and cords.

The dictionary defines constant as uniform and unchanging,
and continuous as uninterrupted. Nonetheless, some dual-wire
resistance monitors utilize a pulsed test current and do not
really 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 ESD events 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 microprocessor.”* The dual-wire system does not meet
all industry ESD S6.1 specifications, as the cords do not
meet the EOS/ESD Association guidelines for the 1 to 5
pound “breakaway force” requirement for ensuring a reliable
path-to-ground and preventing accidental disconnects.

By using the reliable wave distortion 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 specific 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.

*1981 article by Donald E. Frank - Electrical Overstress Electronic

Discharge Symposium Proceedings

Installation

Confirm that worksurface(s) is 1 x 10E7 ohms or less and has
a conductive layer. Remove the monitor from its packaging
and inspect for any shipping damage. Included with each Dual
Operator and Dual Workstation Continuous Monitor should be:

1 Monitor Control unit
2 Satellite remote monitors with 6 mounting screws (19248)
2 7ft. remote cables for connection to satellites
1 120 / 220 VAC transformer
2 6' Work surface ground cord with additional ring terminals
2 6' Ground cord
4 Push and clinch snap (09863)
4 Counter Sink Washers
1 Certificate of Calibration

The Model 19246 / 19247 monitor control unit is normally
installed under the bench top toward the front edge of a
workstation where the LEDs are easily visible. The unit is
designed to be mounted using the flanges (See Figure 2).

Screws

Figure 2. Mounting the monitor

Figure 3 shows the monitor as it is viewed from the front.

Figure 3. Operating the 19246 / 19247 monitor

SATELLITE REMOTE
MONITORS.

The Satellite remote
monitors can be installed
up to 7 feet away from
the monitor control unit.
Two operators plus
two worksurfaces can be monitored at separate adjacent
workstation mat circuit maybe bypassed by a switch located
at the rear of the satellite. The satellite remote monitors are
available separately as item 19248. Also shown on each

TB-3058 Page 2 of 4

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

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

© 2011 DESCO INDUSTRIES INC.

Employee Owned