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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
DESCO EAST - One Colgate Way, Canton, MA 02021-1407 • (781) 821-8370 • Fax (781) 575-0172 • Web Site:
TB-3058 Page 2 of 4
DESCO WEST - 3651 Walnut Avenue, Chino, CA 91710 • (909) 627-8178 • Fax (909) 627-7449
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
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
/
19247
monitor
Desco.com
© 2011 DESCO INDUSTRIES INC.
Employee Owned
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