Desco 19240 Installation Manual

TECHNICAL BULLETIN TB-3017

Wrist Strap Tester - Operation, Installation
and Calibration Instructions

Pass Range 800K Ohms to 10 Megohms, 9 Volt Battery Operation

The Wrist Strap Tester
is a battery operated
“on demand” wrist strap
tester. When the wearer
of a wrist strap plugs
in their coil cord and
touches the metallic
surface of the Wrist
Strap Tester, a path for
current flow is completed
from the wearer’s skin,
through the wrist strap.
This action will cause the
green “test good” LED
to light as long as the
resistance of the circuit
path is between 800k
ohms and 10 megohms.

Made in America

Figure 1. Model 19240 Wrist Strap Tester

Description

Per ANSI/ESD S20.20, test equipment is required to
enact the Compliance Verification Plan Requirement. Test
equipment shall be selected to make measurements of
appropriate properties of the technical requirements that are
incorporated into the ESD program plan. The Touch Tester
can be used to fulfil ESD-S1.1, “The wrist strap system
should be tested daily to ensure proper electrical value”
(paragraph 6.1.3). Being a portable battery powered tool,
it is perfect for small labs or for a supervisor to spotcheck
workers and/or ensure compliance.

Installation

The Wrist Strap Tester
is battery powered.
When received, open the
battery compartment and
install the battery, and
you will be ready to test
your wriststraps.

Note: the low battery
indicator flashes every
time the unit is used. When battery fail indicator is constant,
check voltage of battery and/or replace it.

Figure 3. Recording results.

Operation

A wrist strap cord is plugged into the banana jack. When
the wearer of a wrist strap touches the metallic test button,
the green “test good” LED will light if the operator-to-ground
resistance is between 800k ohms and 10 megohms.
If the operator-to-ground resistance is below 800K, the
red “LOW” LED will light and the alarm will sound. If the
operator-to-ground resistance is above 10M, the red “HIGH”
LED will light and the alarm will sound. Per ESD Handbook
TR20.20 paragraph 5.3.2.4.3 Test Procedure, “If the [wrist
strap test] resistance is still too high, dry skin might be the
problem. Dry skin conditions can be resolved by applying
moisturizing lotion on the wrist and repeating the resistance
test again. The moisturizing lotion should be one that is
compatible with process requirements.” If after application
of ESD lotion such as Reztore™ ESD Hand Lotion, the
resulting test is still fail “HIGH” or fail “LOW”, the operator
should notify their supervisor to have the wrist strap and cord
checked.

Figure 2. Testing a wrist strap

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

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

TB-3017 December 2009 Page 1 of 2

© 2009 DESCO INDUSTRIES INC.

Employee Owned

Calibration

We recommend annual calibration of our testers. The model
19240 is calibrated to NIST traceable standards. Calibration
may be performed to ensure that the tester is operating
within limits.

If you are familiar with the procedure, the following resistance
should give the display shown:

Resistance Value (±1%) Test Output
750 Kilohms: Red (Low-hazard)
850 Kilohms: Green (OK-in limits)
9 Megohms: Green (OK-in limits)
11 Megohms: Red (High resistance)

Procedure

Connect the test resistance from the banana jack to the test
button. With resistance applied and test button pressed,
display should yield proper output. Make sure test clips are
insulated from users hands.

A unit failing the calibration test will need to be returned to
the manufacturer.

ESD Handbook TR 20.20 paragraph 5.3.2.4.2 Additional
User Wrist Strap Testing, “Proper testing of the wrist strap
includes the resistance of the groundable point on the end
of the cord, the cord itself, the resistor, the cord-to-cuff snap
connector, the resistance of the interface of the cuff, the cuff/
wrist interface, and the resistance of the person between the
wrist and the hand that contacts the test electrode. Typically,

the maximum acceptable resistance most often used for wrist

strap grounding is less than ten megohms.”

The lower limit is to verify that 1 Megohm ±20% current
limiting resistor is in the resistance. Typically, the minimum
acceptable resistance most often used for wrist strap
grounding is greater than 800 Kilohms (Ref: ANSI/ESD
S20.20 Table 1).

LIMITED WARRANTY

Desco expressly warrants that for a period of one (1)

year from the date of purchase, Desco Wrist Strap
Testers will be free of defects in material (parts) and
workmanship (labor). Within the warranty period, a
unit will be tested, repaired or replaced at Desco’s
option, free of charge. Call Customer Service at
909-627-8178 (Walnut, CA) or [phone]
(Canton, MA) for a Return Material Authorization
(RMA), and proper shipping instructions and address.
You should include a copy of your original packing
slip, invoice, or other proof of purchase. Any unit
under warranty should be shipped prepaid to the
Desco factory. Warranty replacements will take

approximately two weeks.

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.

TB-3017 Page 2 of 2

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]

© 2009 DESCO INDUSTRIES INC.

Employee Owned