TECHNICAL BULLETIN TB-3027
Dual Operator Workstation Continuous Monitor with
Satellites - Operation, Installation and Maintenance
Made in America
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).
Figure 1. Desco Dual Operator Continuous Monitor with
Satellites
ADVANTAGES OF CONTINUOUS MONITORING
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.
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
19232
19233
Voltage AC
120 Volt
220 Volt
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
19232
is powered by a 120 VAC, 60/50 Hz, plug-in transformer which
also provides connection to ground.
*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 applications.
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.”
DESCO WEST
- 3651 Walnut Avenue, Chino, CA 91710 • (909) 627-8178 • Fax (909) 627-7449
DESCO EAST
- One Colgate Way, Canton, MA 02021-1407 • (781) 821-8370 • Fax (781) 575-0172 • Website:
Desco.com
© 2010 DESCO INDUSTRIES INC.
Employee Owned
TB-3027
April 2010 Page 1 of 4
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.
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
2
2
1
2
2
4
4
1
Monitor Control unit
Satellite remote monitors with 6 mounting screws (19235)
7ft. remote cables for connection to satellites
120 / 220 VAC transformer
6' Work surface ground cord with additional ring terminals
6' Ground cord
Push and clinch snap (09863)
Counter Sink Washers
Certificate of Calibration
The Model
19232
/
19233
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
19232
/
19233
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
19235.
Also shown on each
*1981 article by Donald E. Frank - Electrical Overstress Electronic
Discharge Symposium Proceedings
DESCO WEST
- 3651 Walnut Avenue, Chino, CA 91710 • (909) 627-8178 • Fax (909) 627-7449
DESCO EAST
- One Colgate Way, Canton, MA 02021-1407 • (781) 821-8370 • Fax (781) 575-0172 • Web Site:
Desco.com
© 2010 DESCO INDUSTRIES INC.
Employee Owned
TB-3027
Page 2 of 4
satellite remote unit is a supervisor ground connection jack
where a supervisor, guest, or equipment can be grounded.
Figure 4 shows the monitor control unit as it is viewed from the
rear, with the work surface wiring in place.
5. A convenient 3-wire 120 VAC outlet should be located and
tested for proper wiring and grounding. We recommend Desco
Item
98130
AC Outlet Analyzer to verify proper wiring.
6. Plug the transformer into the outlet and connect the plug
into the back side of the monitor control unit. The green Work
Surface LED should be lit. The monitor control unit is now
ready for use. If the red Work Surface LED is flashing, check
the snap fastener and ground cords for proper connection.
TO
POWER
ADAPTER
Installation on Micastat
®
Laminate
Materials Needed:
2 Flush Mount Ground Laminate Inserts
1 Installation Tool for Flush Mount Insert
1. Install the Flush Mount Inserts first. It is recommended to
install one in the right back corner and the other in the left back
corner of the Micastat
®
laminated bench top.
2. Once both inserts are installed, cut the ground cord supplied
with the monitor into two pieces; make sure that the tinned end
is long enough to connect from the worksurface terminal on
the Satellite Remote Unit to one of the flush mount terminals
located under the bench.
3. The remaining wire can then be used to connect the other
flush mount terminal to ground using the supplied ring terminal.
The shrouded molded end can then be cut off.
When complete, one flush mount terminal will connect the
Micastat
®
laminate to ground while the other will connect
it to a satellite remote unit. The satellite remote unit then
monitors the ground connection between the two inserts,
and since Micastat
®
is the only ESD laminate made with
a physical uniform ground layer, it will monitor the entire
Micastat
®
surface ground. The wires will stay under the bench,
maximizing the usable space on the bench top.
WORKSTATION #2
WORKSTATION #1
Figure 4. Wiring connection instructions for the
19232
/
19233
monitor control unit.
The following procedure will outline how to correctly wire the
19232
/
19233
monitor control unit to properly monitor an ESD
protected workstation.
1. Use the rear phone jack connections and connect the
Satellite Remote Units to the base unit with the phone cables.
See Figure 4 for wiring connection instructions.
2. Mat monitoring may be bypassed by using the switch
located inside a 1/4” hole at the rear of the satellite.
3. Verify that a ground cord is properly connected to snap
socket on one corner of the ESD worksurface. The other end
of the ground cord is to be attached to the workbench common
point ground. After Satellite Remote Units are mounted, route
wires using a direct route; try to avoid running wires adjacent
to metal.
4. Confirm that worksurface surface resistance is 1 x 10E7
ohms or less. Connect the ring terminal end of the worksurface
cord included with the unit to the screw on the back of the
satellite. Snap the other end to the worksurface grounding
point as shown in Figures 4 and 5.
Screw allows
ground cord to
be bolted to mat;
keeps cord from
disconnecting.
Operation
When the satellite remote unit is installed and is connected to
a grounded ESD protective work surface, the monitor’s green
Work Surfaces LED’s and its two red Operator LED’s should
be on.
The monitor takes 6 seconds to activate its alarm
circuitry when it is first plugged in.
or
To use the monitor:
1. Plug a wrist strap cord, into either of the Satellite remote
units marked “OPERATOR” on the front of the Satellite
remote unit. This automatically activates the selected operator
channel. The red Operator LED should turn on and the audio
alarm should beep.
2. Remove the charges from your body by making contact
with a properly grounded ESD worksurface. Snap the cord
to the wristband, which should fit snugly on your wrist. This
should silence the alarm and cause the LEDs to switch from
red to green. If this does not happen, check the coil cord for
continuity or damage. Examine your wristband and ensure that
it has a secure fit. If you have dry skin use ESD hand lotion
such as Menda Item
35660
Reztore™ ESD Hand Lotion.
When leaving the area a person can take the coil cord along
or unsnap the cord from wristband and attach the socket to
the Satellite remote unit snap that is labeled “Park”. This will
de-activate the alarm and allow you to leave the station. If the
cord is plugged into the jack marked “Operator” the monitor will
TO SATELLITE
Figure 5. Installing cords on the worksurface.
DESCO WEST
- 3651 Walnut Avenue, Chino, CA 91710 • (909) 627-8178 • Fax (909) 627-7449
DESCO EAST
- One Colgate Way, Canton, MA 02021-1407 • (781) 821-8370 • Fax (781) 575-0172 • Web Site:
Desco.com
© 2010 DESCO INDUSTRIES INC.
TB-3027
Page 3 of 4
Employee Owned
alarm continuously until you either park the cord, or remove the
cord from the operator jack. In the case of removing the cord
from the jack, the audio alarm will only sound for approximately
eight seconds.
Whenever the coil cord is accidentally withdrawn from the jack,
or if continuity from the user to the satellite remote unit is not
maintained, the alarm sounds, the green Operator LED turns
off and the red Operator LED turns on.
Maintenance and Calibration
Work Surface Channel
The
19232
/
19233’s
Work Surface monitoring circuitry is
sufficiently sensitive to detect extremely low current, allowing
it to be used with mats having a resistance of up to 1x 10E7
ohms (10 megohms). If user desire not to monitor worksurface,
mat circuit can be bypassed with switch, located at the rear of
the satellite.
When the monitor is connected to a static dissipative work
surface, the amount of current that flows is a function of the
total resistance between the monitor and through the work
surface to ground. When the resistance of the work surface
is below a present 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
fields. The resistance threshold is factory set to 10 megohms
(1 x 10E7 ohms). Custom worksurface range available upon
request. Call for details.
Note:
Per ESD S6.1, Grounding paragraph 4.1.1 “Every
element to be grounded at an ESD protected station shall
be connected to the same common point ground.” The
ESD control plan should include a tailoring** statement
that continuous monitors are used and that consistent with
manufacturer’s design grounding is via AC adapter cord to
equipment ground.
The Dual Operator Workstation Continuous Monitor is solid
state and designed to be maintenance free. The
19232
and
19233
are calibrated to NIST traceable standards. There
are no user adjustments that can be made. Because of
the impedance sensing nature of the test circuit, special
equipment is required for calibration. We recommend using the
Desco
98220
Continuous Monitor Calibration Unit whenever
calibration is performed annually or any of the satellite remotes
are replaced. The Calibration Unit is a most important
product which allows the customer to perform NIST traceable
calibration on continuous monitors and can be used to fulfill
ANSI/ESD S20.20 Paragraph 6.2.2.2 Personnel Grounding
Guidance, “Personnel should check constant monitoring
devices (when used) to ensure that they are functional and
operating before ESDS products are handled. In addition,
constant monitoring devices should be functionally checked
periodically to ensure that they are operating as designed.”
The Desco
98220
is designed to be used on the shop floor at
the workstation, virtually eliminating downtime, verifying that
the continuous monitor is operating within tolerances.
† This cannot be verified with standard DC test equipment. The
continuous monitor is an impedance sensing device and the limits
are determined by the magnitude and angle of the impedance.
*Contact factory for special limits.
Limited Warranty
Specifications
Test range of monitored circuit
Supervisor Jack
Resistance to Ground
Work Surface Limit*
Operating Voltage
Wrist strap open circuit voltage
Mat test open circuit voltage
Response time to alarm
Operating Temperature
Long Term Drift
500K - 10M ohms†
47k ohms typical
Set to 10 Megohms
(1 x 10E7 ohms)
120 VAC, 50-60 Hz
1.2 volts peak to peak @
1-2 MicroAmps
5 to 7.5 volts
< 50 mS
0 - 40°C
<0.5% per Decade
(1st Decade is 1 hr)
Desco expressly warrants that for a period of one (1) year from the
date of purchase Desco Continuous Monitors will be free of defects in
material (parts) and workmanship (labor). Within the warranty period,
a credit for purchase of replacement Desco Continuous Monitors, or, at
Desco’s option, the Continuous Monitor will be repaired or replaced free
of charge. If product credit is issued, the amount will be calculated by
multiplying the unused portion of the expected one year life times the
original unit purchase price. Call our Customer Service Department at
909-627-8178 (Chino, CA) or 781-821-8370 (Canton, MA) for a Return
Material Authorization (RMA) and proper shipping instructions and
address. Please include a copy of your original packing slip, invoice,
or other proof of date of purchase. Any unit under warranty should be
shipped prepaid to the Desco factory. Warranty replacements will take
approximately two weeks.
If your unit is out of warranty, call our Customer Service Department at
909-627-8178 (Chino, CA) or 781-821-8370 (Canton, MA) for a Return
Material Authorization (RMA) and proper shipping instructions and
address. Desco will quote repair charges necessary to bring your unit up
to factory standards.
Warranty Exclusions
Note:
Work surface must have a conductive layer such as
Dual Layer Rubber or Dissipative 3-Layer Vinyl or Micastat®
Dissipative Laminate with conductive buried layers. Desco
Continuous Monitors are not recommended for use with
homogeneous matting.
THE FOREGOING EXPRESS WARRANTY IS MADE IN LIEU OF
ALL OTHER PRODUCT WARRANTIES, EXPRESSED AND IMPLIED,
INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE WHICH ARE SPECIFICALLY DISCLAIMED. The express
warranty will not apply to defects or damage due to accidents, neglect,
misuse, alterations, operator error, or failure to properly maintain, clean
or repair products.
Limit of Liability
In no event will Desco or any seller be responsible or liable for any injury,
loss or damage, direct or consequential, arising out of the use of or
the inability to use the product. Before using, users shall determine the
suitability of the product for their intended use, and users assume all risk
and liability whatsoever in connection therewith.
DESCO WEST
- 3651 Walnut Avenue, Chino, CA 91710 • (909) 627-8178 • Fax (909) 627-7449
DESCO EAST
- One Colgate Way, Canton, MA 02021-1407 • (781) 821-8370 • Fax (781) 575-0172 • Web Site:
Desco.com
© 2010 DESCO INDUSTRIES INC.
Employee Owned
TB-3027
Page 4 of 4
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