Desco 19228 Technical Bulletin

TECHNICAL BULLETIN TB-3054

Multi-Mount Continuous Monitor
Operation, Installation, and Maintenance

ADVANTAGES OF CONTINUOUS MONITORING
OVER PERIODIC TESTING

Many customers are eliminating periodic testing 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 failures after ESD susceptible
products have been manufactured. The costs of dealing
with the resulting catastrophic or latent defects can be
considerable. Multi-Mount Continuous Monitors eliminate
the need for users 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
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

Figure 1. Desco 19228 Multi-Mount Continuous Monitor

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 19228 Multi-Mount Continuous
Monitor continuously monitors the integrity of one operator.
This monitor will provide virtually instantaneous notification
of static control equipment failures, eliminating the need
of periodic testing and costly record keeping. This unit
is highly cost effective as it is designed to monitor any
conventional single wire wrist strap and ground cord
system. Its small package and mounting tabs with holes
make it highly suitable to install on most any equipment
or work bench surface. In addition, optional mounting is
available using the provided adhesive-backed Velcro®
strips. Using either mounting method makes the
Multi-Mount Monitor suitable for most any machinery or
workbench even in hard to reach locations.

The Multi-Mount Continuous Monitor is a real time
instrument that ensures that critical ESD generators in a
sensitive area are effectively grounded. The instant an
operator’s wrist strap or cord fails, the monitor will issue
audible and visual (LEDs) alarms alerting the user and
supervisor of the problem.

The Parking Snap features provides a means for the
operator to disconnect wrist strap cord when normally
leaving work area without audible alarm sounding. It also
provides a means of wrist strap cord storage.

omitted if constant monitoring is used.”

WAVE DISTORTION DETECTION TECHNOLOGY
PROVIDES TRUE 100% CONTINUOUS MONITORING

From all the technical alternatives available, Desco
has chosen wave distortion technology for many of its
Continuous Monitor product offerings. 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 Multi-Mount
Continuous Monitor will reliably determine if the circuit is
complete.

Wave distortion technology can be referred to “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 Multi-Mount Continuous Monitor cannot be
“fooled”. It will provide a reliable alarm only when the
wrist strap becomes dysfunctional or unsafe according to
accepted industry standards. The Multi-Mount Continuous
Monitor is drift-free and designed to be insensitive to the
effects of squeezing or stretching the coil cord.

Made in America

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

TB-3054 July 2011 Page 1 of 4

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

© 2011 DESCO INDUSTRIES INC.

Employee Owned

ADVANTAGES OF WAVE DISTORTION AND
SINGLE-WIRE TECHNOLOGY

The Desco Multi-Mount 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 expensive &

fragile dual-wire cords and special wrist straps. Dual-wire

cords are expensive and are the weak link of the system,

the most likely component to need replacement. Over a
five year period, this can make the dual-wire system three

to five times as expensive as a system utilizing single-wire

wrist straps and cords. See Maintenance and Calibration
(page 4) to minimize life-cycle costs.

The dictionary defines constant as uniform and unchanging,
and continuous as uninterrupted. None theless, 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 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.*
The dual-wire system does not reliably meet all industry
specifications, as the cords do not meet the EOS/ESD
S-1.0 paragraph 4.1.6, 1 to 5 pound “breakaway force”
requirement for operator safety.

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.

WORKSURFACE CHANNEL

The Multi-Mount Continuous Monitor’s circuitry is

sufciently sensitive to detect extremely low current,

allowing it to be used with mats having a resistance

of up to 1.0 x 10E7 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 10 megohms. (It can be
special ordered to other limits. Limits can be varied

and set to 1 gigohm maximum).

Packaging

1 Multi-Mount Monitor
1 24VAC Power Adapter
1 6' Mat Monitor Cord (Black)
1 6' Mat Ground Cord (Green and Yellow)
2 Push and Clinch Snaps
2 Mounting screws
2 Countersink Washers
1 Set of hook and loop fasteners
1 Certificate of Calibration

Features and Components

H

A

B

EDC

Figure 2. Multi-Mount Continuous Monitor features and
components

A. Status LEDs: When the green LED is illuminated,
the operator is properly grounded. When the red LED is
illuminated, the operator is not properly grounded.

B. Monitored Operator Jack: Where the operator inserts
the wrist cord banana plug.

C. Worksurface Ground LEDs: When the green LED
is illuminated, the worksurface mat is properly grounded.
When the red LED is illuminated, the worksurface mat is not
properly grounded.

D. Operator Ground LEDs: When the green LED is
illuminated, the operator is properly grounded. When
the red LED is illuminated, the operator is not properly
grounded.

E. 4mm Parking Snap: When touched by the operator, this

snap will deactivate the alarm for six seconds. This allows

time for the operator to disconnect the coil cord from the
wrist band and park it on this snap. While parked, the coil
cord disables the alarm, allowing the operator to leave the
workstation. The OPERATOR GROUND LED will remain off
while the cord is parked. Upon returning and removing the

coil cord from the parking snap, the operator has six seconds

to hook up to the wrist band before the alarm sounds.

*1981 article by Donald E. Frank - Electrical Overstress / Electronic
Discharge Symposium Proceedings

G
F

TB-3054 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

F. 24 VAC Power Jack: Connect the power adapter here.
G. Mat Connection: Monitors worksurface mat. NOTE: To

disable worksurface monitoring, shunt this terminal to the
neighboring GND terminal with bus wire.

H. Mat Ground: Grounds worksurface mat.

Installation

Remove the monitor from its packaging and inspect for
any shipping damage. Confirm that the work surface is 1

x 10E7 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.

1. A convenient 120VAC outlet should be located and
tested for proper wiring and grounding. We recommend
Desco Item 98130 AC Outlet Analyzer to verify proper
wiring and ground.

2. The Multi-Mount Continuous Monitor may be mounted
to a convenient location using the included mounting
screws or Velcro® set. See Figure 3 for installation
set-up.

3. Install Screws and Washers or Push and Clinch snaps
12 to 72 inches apart from each other on the work
surface mat. Make sure that they pierce and clinch the
bottom side of the mat (see Figure 3).

4. Route the black ground cord to the monitor’s green
terminal block labeled MAT.

5. Route the green ground cord to the monitor’s green
terminal block labeled GND.

6. Connect the power adapter to the monitor’s power jack
labeled “24VAC” and the other end to a proper voltage
source.

Screw allows ground cord to be

or

bolted to mat; keeps cord from
disconnecting.

Figure 4. Installation method #2 of the Multi-Mount
Continuous Monitor

Operation

When the Multi-Mount Continuous Monitor is installed to
an ESD protective worksurface and grounded via a power
cord, the green WORKSURFACE GROUND LED and red
OPERATOR GROUND LED should be illuminated. The
monitor takes 6 seconds to activate its alarm circuitry when
it is first plugged in.

The worksurface resistance is measured between the two
cords installed to the mat worksurface (see Figure 3).

TO USE THE MONITOR

1. Plug a wrist strap cord banana plug into the
monitored banana jack on the front of the unit. This
automatically activates the selected operator
channel. The red operator LED should turn on.

2. Remove the charges from your body by making
contact with a properly grounded ESD worksurface.

Snap the cord to the wristband, and t it snugly onto

the wrist. This should silence the audio and cause
the LEDs to switch from red to green. If this does
not happen, check the coil cord for continuity or

damage. Examine the wrist strap and conrm
that it has a secure t. If you have dry skin, apply

an approved dissipative hand lotion such as Menda
35666 Reztore™ ESD Hand Lotion. When leaving
the area, a person can take the coil cord along or
leave it attached to the monitor in park position.

10mm snaps need to pierce and clinch
bottom side of mat. Snaps need to be
12 to 72 inches apart

Work Surface Mat

Figure 3. Installation method #1 of the Multi-Mount
Continuous Monitor

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

TB-3054 Page 3 of 4

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

Power Adapter
Connection

NOTE: Removing the banana plug from the monitor’s

operator jack will disable the audio alarm.
It is recommended that you use the Park Snap rather

than continuously removing the banana plug from
its jack. Doing so will increase the life span of the
operator jack. If your process requires the constant
insertion and removal of the banana plug, please
contact your Desco Representative for alternate
solutions.

© 2011 DESCO INDUSTRIES INC.

Employee Owned

Specifications:

Distributed by: All-Spec Industries
5228 US Hwy 421 N
Wilmington, NC 28401
[email protected]
www.all-spec.com
PH: 800-537-0351
FX: 800-379-9903

Test range of monitored circuit 500K - 10M ohms†
Operating Voltage

19228 120 VAC, 50/60 Hz
Worksurface Range 10 Megohms
Wrist strap open circuit voltage 1.2 volts peak to peak @

1-2 MicroAmps
Mat test open circuit voltage 5 to 7.5 volts
Response time to alarm <50 ms
Operating Temperature 0 - 40°C

Size 3.86"L x 2.10"W x .910"H

† 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.

NOTE: Worksurface 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.

Maintenance and Calibration

The Multi-Mount Continuous Monitor is solid state and
designed to be maintenance free. The 19228 is calibrated
to NIST traceable standards. There are no user adjustments
neccesary. Because of the wave distortion sensing
nature of the test circuit, special equipment is required for
calibration. We recommend that calibration be performed
using the Desco 98220 Continuous Monitor Calibration
Unit. The Calibration Unit is a convenient product which
allows the customer to perform NIST traceable calibration
on continuous monitors. The 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. Per 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.”

Figure 5. Using the Multi-Mount Continuous Monitor

Limited Warranty

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

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 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]

TB-3054 Page 4 of 4

© 2011 DESCO INDUSTRIES INC.

Employee Owned