Desco 19325, 19326 Installation, Operation And Maintenance Manual

TECHNICAL BULLETIN TB-3060

Full-Time Continuous Monitor
Installation, Operation and Maintenance

ADVANTAGES OF WORKSTATION CONTINOUS
MONITORING OVER PERIODIC TESTING

Many customers are eliminating periodic testing and are
utilizing workstation continuous monitoring to better ensure
that their products were manufactured in an ESD controlled
environment. Full time workstation continuous monitoring is
superior to pulsed monitoring as well as periodic testing, and
can save a significant amount of money in testing costs and
rejected products. 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. Full Time 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 Paragraph 6.2.2.2. test logging
requirements. Per ESD-S1.1 paragraph 6.1.3 Frequency

Figure 1. Desco Full-Time 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 Full Time Continuous Monitor
provides 100% monitoring of both the operator and the work
surface. This unit provides continuous monitoring of:

• One user wearing a wrist strap

• ESD worksurface

• Ground

• AC outlet

Note: Worksurface must have a conductive layer such as
Dual Layer Rubber, Dissipative 3-Layer Vinyl or Micastat®
Dissipative Laminate with conductive buried layers. Desco
Continuous Monitors are not recommended for use with
homogeneous matting.

If the unit detects that the elements are outside industry
standards, the continuous monitor will alarm woth both an
audible alarm and an illuminated red LED to notify the user
of a problem.

Unlike many units, the Full Time Continuous Monitor also
continuously verifies ground (AC outlet ground). When the
Power Cord is plugged in, a self-test runs automatically.
If the AC outlet is wired incorrectly, both red LEDs will
illuminate and the audible alarm will sound. The unit has an
additional ground point for a user or supervisor.

The Full Time Continuous Monitor is available in two
models:

Item Input Voltage Power Cord

19325 120VAC North America

19326 220VAC United Kingdom

of Functional Testing “Daily (Wrist Strap) testing may be
omitted if constant monitoring is used.”

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, and then continuous monitoring should be
considered or even required.”

WAVE DISTORTION DETECTION TECHNOLOGY
PROVIDES TRUE 100% CONTINUOUS MONITORING

Desco utilizes wave distortion technology for the Full Time
Continuous Monitor, which is an Impedance type monitor.

Per ESD TR12-01 section 2.2 Impedance (or single wire)
constant monitors “The capacitance type of monitor is
also known as an impedance monitor. They both work on
the same theory, however the impedance monitor uses
a detection circuit designed to reduce false alarms and
eliminate adjustments. ‘Single Wire’ or ‘impedance type’
monitors use the phase difference between current and
voltage to detect changes in impedance of the cord, band
and person. A very low AC voltage is used for constant
sensing. Any standard wristband and coiled cord can be
used.”

Thus the 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 Full Time Continuous Monitor will reliably determine
if the circuit is complete.

Made in the

United States of America

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

TB-3060 Page 1 of 5

July 2018

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

© 2018 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.

Packaging

1 Full-Time Continuous Monitor
1 Power Cord
1 Mat Monitor Cord (Black)
1 Ground Cord (Green and Yellow)
2 Countersunk Washers
2 Flat Head Screws, 6-32 x 1/4"
1 Hook and Loop Fastener Strip
1 Certificate of Calibration

In normal factory environments, and with persons whose
capacitance with respect to ground is within design limits (5

Features and Components

feet tall 90 pound person to 6 foot 5 inch 250 pound person),
the Full Time 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 Full Time 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 Full Time 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 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
Calibration section on 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”

Figure 2. Full-Time Continuous Monitor features and
components

A. IEC Power Cord Inlet: Connect the power cord here.

B. I/O Signal Output: Contact Desco Customer Service for

more information

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”.* Some dual-wire systems do
not reliably meet all industry specifications, as the cords may
not meet the EOS/ESD S-1.0 paragraph 4.1.6 one to five

C. Monitored Ground Terminal: Grounds the worksurface
mat. Connect the green and yellow ground cord here.

D. Monitored Mat Terminal: Monitors the worksurface mat.
Connect the black mat monitor cord here.

E. Mat Ground LEDs: When the green LED is illuminated,
the worksurface mat is properly grounded. When the red
LED is illuminated and the alarm sounds, the worksurface
mat is not properly grounded.

pound “breakaway force” requirement for operator safety.

F. Operator Ground LEDs: When the green LED is

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

illuminated, the operator is properly grounded. When the
red LED is illuminated and the alarm sounds, the operator
is not properly grounded.

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

G. Auxiliary Ground: Unmonitored banana jack ground
point.

extremely safe for use in voltage sensitive applications such
as disk drive manufacturing.

A

G H I

B C

D

E

F

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

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

TB-3060 Page 2 of 5

© 2018 DESCO INDUSTRIES INC

Employee Owned

H. 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.

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

Installation

Remove the monitor from its packaging and inspect for
any shipping damage. Confirm that the worksurface is
10 megohms 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. Locate a nearby power outlet and test it for proper wiring
and grounding. We recommend the Desco AC Outlet

Analyzer to verify proper wiring and ground.

Must be 12-72" apart

2. Connect the tinned wire termination of the Ground Cord
to the GND terminal block on the monitor.

Figure 3. Wiring the Full-Time Continuous Monitor to a
worksurface mat

3. Connect the tinned wire termination of the Mat Monitor
Cord to the MAT terminal block on the monitor.

50547 RELAY BOX

4. Determine the mounting location of the Full-Time
Continuous Monitor. It is normally installed toward the
front edge of a workstation where its LEDs can be visible
to the operator. Use the included hook and loop strip if
desired.

5. Use a blade to pierce two holes 12" to 72" apart from
one another into the worksurface mat.

6. Use a Phillips screwdriver to secure the two flathead
screws and countersunk washers through the
worksurface mat and into the threaded 10mm snaps on
the underside of the Mat Monitor Cord and Ground Cord.

7. Connect the power cord to the power inlet located on the
top-side of the Full-Time Continuous Monitor. Connect
the opposite end of the power cord to the tested AC
outlet.

NOTE: Older revision Full-Time Continuous Monitors
included push and clinch snaps instead of countersunk
washers and flat head screws to secure the mat monitor cord
and ground cord to the worksurface mat.

Figure 4. EMIT 50547 Full-Time Continuous Monitor
Relay Box

The Full-Time Continuous Monitor can be equipped with
the EMIT 50547 Relay Box to control electronic door locks,
lights, buzzers, etc. The relay will activate when a failure is
caught by the Full-Time Continuous Monitors.

Maximum Switching Current:
1A @ 30VDC or .3A @ 125VAC

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

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

TB-3060 Page 3 of 5

Contact Form:
2 Form C

© 2018 DESCO INDUSTRIES INC

Employee Owned

Normally

Closed

Input Jack

Normally
Closed

USING THE MONITOR

1. Plug a wrist strap cord, not attached to the wristband, into
the monitored banana jack labeled OPERATOR on the
front of the unit. This automatically activates the selected
operator channel. The red operator LED should illuminate,
and the audible alarm will sound after the activation
period.

Common

Common

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

Normally

Open

Normally
Open

cord to the wristband, and fit it snugly onto your wrist.
This should silence the audible alarm and cause the
OPERATOR GROUND LED to switch from red to green.
If this does not happen, examine the wrist cord for

Figure 5. Full-Time Continuous Monitor Relay Box
features and components

continuity or damage and your wrist band to ensure
that it is securely fit. If you have dry skin, apply an
approved dissipative hand lotion such as Menda

1. Remove the cover from the Relay Box.

2. Tie wire around the necessary contacts inside the Relay
Box.

3. Route the wire out the bottom of the Relay Box and
close the cover.

4. Make the proper connections to your targeted device
(light fixture, door lock, etc.). Use Figure 6 as a guide.

5. Power the Full-Time Continuous Monitor after installation
is completed.

Reztore™ ESD Hand Lotion. When leaving the area,

the user can take the wrist cord along or attach it to
the monitor parking snap. The audible alarm will shut
off when operator wrist cord is removed from unit and or
when the cord is attached to the parking snap.

NOTE: Removing the banana plug from the monitor’s
operator jack will disable the audible alarm.

PARKING SNAP

All Desco single-wire monitors with wave distortion
technology include the Park Snap feature. Use the Park
Snap to store the operator’s wrist cord and enable standby

Phone Cord

Light Fixture

mode while the operator is away from the workstation.
Before disconnecting the coil cord from the wristband, the
operator touches the Park Snap to disable the audio alarm
for 6 seconds. Within the 6 second period, the operator can
disconnect their wrist cord from their wristband and attach it

Green Light

Red Light

to the Park Snap before the audible alarm sounds.

WORKSURFACE CHANNEL

The Full Time Continuous Monitor’s circuitry is sufficiently

Relay Box

sensitive to detect extremely low current when used with a
worksurface with a conductive layer.

5-24V

Note: The monitor will not detect insulative contamination

Full-Time

Continuous Monitor

Figure 6. Installing the Relay Box and Full-Time
Continuous Monitor to a Light Fixture

Power Supply Furnished

with Light Fixuture

on the worksurface. “Insulative contamination can increase
the resistance to ground making the worksurface ineffective.”
(ESD TR12-01 section 3.1 Worksurface monitors). ESD
worksurfaces should be kept clean using an approved ESD
cleaner like Reztore™ Antistatic Surface & Mat Cleaner.
When the monitor is connected to an ESD worksurface,

Operation

When the Full-Time Continuous Monitor is installed to an
ESD protective worksurface and grounded via a power
cord, the green MAT GROUND LED and red OPERATOR
GROUND LED should illuminate. The monitor takes 6
seconds to activate its alarm circuitry when first powered.

• Correct wiring of the outlet is confirmed when the monitor

is plugged in.

• The worksurface resistance is measured between the two

snaps installed to the mat worksurface.

the amount of current that flows is a function of the total
resistance between the Continuous Monitor and through
the worksurface to ground. When the resistance of the
worksurface is below a pre-set threshold, the monitor will
indicate Pass. Conversely, if the resistance level is high
when compared to the monitor’s reference, the unit will fail
and 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. (It can be special ordered to other limits.
Contact manufacturer for specifications).

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

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

TB-3060 Page 4 of 5

© 2018 DESCO INDUSTRIES INC

Employee Owned

Calibration

Frequency of recalibration should be based on the critical
nature of those ESD sensitive items handled and the risk of
failure for the ESD protective equipment and materials. In
general, Desco recommends that calibration be performed
annually.

Use the Desco 98221 Wave Distortion Monitor Verification

Specifications

Input Voltage and
Frequency

Operating Temperature 50 to 95°F (10 to 35°C)

Environmental
Requirements

Tester to perform periodic verification (once every 6-12
months) of the Full-Time Continuous Monitor. The verification
tester can be used to check the test limits of the Full-Time
Continuous Monitor without removing it from the workstation.

See TB-3074 for more information.

Dimensions 4.38" L x 3.25" W x 0.89" H

Weight 0.26 lbs. (0.12 kg)

Operator Test Range* 500 kilohms to 10 megohms

Worksurface Test Limit** 10 megohms (±10%)

Operator Test Voltage 1.2V peak-to-peak @ 1.2µA,

Worksurface Test
Voltage

Alarm Response Time <50 ms

Country of Origin United States of America

100-120VAC, 50/60 Hz

Indoor use only at altitudes less
than 6500 ft. (2 km)

Maximum relative humidity
of 80% up to 85°F (30°C)
decreasing linearly to 50% @
85°F (30°C)

(111 mm x 83 mm x 23 mm)

impedance

open circuit

5 to 7.5V, open circuit

Figure 7. Desco 98221 Wave Distortion Monitor

Verication Tester

*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.

**The worksurface mat must have a conductive layer such
as Dual Layer Rubber or Dissipative 3-Layer Vinyl with
conductive buried layers. Desco workstation monitors are not
recommended for use with homogeneous matting.

Limited Warranty, Warranty Exclusions, Limit
of Liability and RMA Request Instructions

See the Desco Warranty -

Desco.com/Limited-Warranty.aspx

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

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

TB-3060 Page 5 of 5

© 2018 DESCO INDUSTRIES INC

Employee Owned

Mouser Electronics

Authorized Distributor

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