DESCO WEST
- 3651 Walnut Avenue, Chino, CA 91710 • (909) 627-8178
DESCO EAST
- One Colgate Way, Canton, MA 02021-1407 • (781) 821-8370 • Website:
Desco.com
TB-3058
Page 2 of 5
© 2013 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.
Packaging
1 Dual Operator Continuous Monitor (Control Unit)
2 Satellite Remotes (item
19248
)
1 Power Adapter, 24VAC
2 Mat Monitor Cords (Black), 6'
2 Mat Ground Cords (Green and Yellow), 6'
2 Satellite Remote Cables, 7'
4 Push and Clinch Snaps
4 Countersink Washers and Screws (#4 x 1/4")
6 Mounting Screws (#8 x 3/4")
1 Certificate of Calibration
Installation
Remove the monitor and satellites from its packaging.
Inspect for any shipping damage. Confirm that the
worksurface is 1 x 10
7
ohms or less and has a conductive
layer such as Dual Layer Rubber, Dissipative 3-Layer Vinyl,
or Micastat
®
Dissipative Laminate with conductive buried
layers.
The Control Unit for the Dual Operator Continuous Monitor is
normally installed under the bench top toward the front edge
of a workstation where the LEDs are easily visible. Use the
enclosure’s flanges to mount the monitor.
*1981 article by Donald E. Frank - Electrical Overstress Electronic
Discharge Symposium Proceedings
screws
Figure 2. Mounting the Control Unit
Figure 3. Typical setup of the Dual Operator Continuous
Monitor and Satellites
