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3M 740 Operating Instructions Manual

Made by: 3M
Type: Operating Instructions
Category: Test Equipment
Pages: 12
Size: 0.11 MB

 

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MO 0765-0601

740

wrist strap + shoe tester

3

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740 Wrist strap + shoe tester

Operating Instructions

MO 0765-0601

April, 2001

 


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MO 0765-0601

740

wrist strap + shoe tester

3

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o.k.

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M

2    -
5    -

10    -
35    -

-     10
-     35
-     50
-  100

on / off

+

-

Output

R

max

DC 24

30 V / 150 mA 

LED for

«too low resistance»

Ground cord
4 mm stud

Contact plate for
wrist strap test

Socket for
wrist strap

Ground Socket

Output signal for external devices
e.g. - data transfer to PC, electrical door
opening system, acoustic signal, etc.

LED

Upper limit
selection for wrist
strap and shoe test

Socket for
shoe electrode

Connection for AC/DC
transformer

On / Off switch

Contact plate
for shoe test

LED for

«too high resistance»

I. General

Personnel grounding devices such as wrist straps
and conductive footwear are the primary method
to minimize charge generation on the human
body. They must be able to drain this charge as
rapidly as it is generated.

For this reason, it is important to test wrist straps
and conductive footwear on a regular basis to
ensure they are functioning properly and that the
test results can be recorded

II. Declaration of Conformity

The 740 Wrist Strap and Shoe Tester is in
conformity with the regulations of the EMC-
directive 89/336/EWG. The following standards
have been taken into account while designing and
manufacturing the instrument:
EN 60204-1/85,
EN 60204-1/91,
EN 61010 (Safety),
EN 50082-1/92 and
EN 50082-2/92.

 


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R

max

III. Description

The 740 wrist strap and shoe tester is an electronic
test instrument which is easy to operate and
designed to be wall mounted. An AC/DC
transformer is supplied. The 740 switches off
automatically after non-use for approximately
30 minutes.

The unit consists of two measurement circuits
with an open circuit test voltage of 20 V for wrist
strap and shoe test applications. For wrist strap
and footwear testing, a minimum threshold
resistance of 750 k

Ω is set internally. The desired

maximum allowable resistance level can be
selected separately for each measurement. If the
resistance of the tested wrist strap or footwear is
within the selected range, the green "o.k." LED
will illuminate. The red "<" LED alerts the
operator that the resistance of the tested device is
under 750 k

Ω. The red ">" LED indicates that the

selected maximum resistance is exceeded.

The 740 can be connected to external devices such
as computers (for data recording), electrical door
opening systems, counter or other evaluating
components.

The 740 wrist strap and shoe tester
consists of:

- Instruction manual with daily log sheet

- Base unit

- Data output connector plug

- Wall mounting kit, 3M Dual Lock™ fastening

system and template

- Cover for wrist strap plug-in jack

- AC/DC transformer

- Ground cord

Accessories:

- Shoe electrode type 741 (single electrode) sold

separately

IV. Operation

Connect the AC/DC transformer (DC 24-30 V,
150 mA) to the 740 tester.

Note: If you notice a delay in the response time of
the LED illumination please connect the ground
cord supplied to the ground socket of the 740.
Please ensure proper earth ground connection!

Switch the unit on. All LEDs will flash for
approximately 1 s to check their function. Select
the desired upper maximum resistance level for
both the wrist strap and shoe test by using a small
screw driver.

The 741 shoe electrode must be connected if
footwear testing is required.

 


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MO 0765-0601

V. Wall Mounting

The enclosed 3M Dual Lock™ fastening discs
must be screwed to the wall using the attached
template approximately 1,500mm (5 feet) above
the floor. Drill three holes of 5 mm (0.2 in)
diameter at marked locations. Make sure the area
on the 740 in which the Dual Lock™ fastening
strips are placed is free of dust and dirt. Attach the
3M Dual Lock™ fastening strips to the rear of the
740 tester to the bottom and top in parallel; see
drawing for locations.

For securing on the wall, press the 740 firmly
against the discs. For removal of the 740, lift the
top corners with both hands.

VI. Wrist Strap Test

Put the wrist band on with ground cord attached
and insert the ground cord into the wrist strap
plug-in jack. Depress the metal contact plate and
hold it. One of the indicator LEDs will illuminate.

An illuminated green LED indicates that the wrist
strap performs within the resistance range of 750
k

Ω to the upper selected value of 2, 5, 10 or 35

M

Ω. If a red "<" LED is illuminated, the current

limiting resistor in the ground cord is bypassed
and the cord has to be replaced. The red ">" LED
indicates that the selected resistance range is
exceeded. Check to see if the high resistance is in
the cord, the wrist band or in the contact between
wrist band and the operator's skin. To check the
resistance of the ground cord, leave the plug end
of the ground cord attached to the tester and
disconnect the snap end from the wrist band.
Connect ground cord snap to the stud in the hand
symbol or press it onto the contact plate and
depress the plate until one of the LEDs is
illuminated.

If the green LED illuminates
now, the ground cord can be
used.

If the red ">" LED is
illuminated, replace the
ground cord.

In some cases, high contact resistance between the
skin and wrist band will cause the tester to show a
red ">" LED condition. This resistance may be
caused by dry skin or the presence of hair in the
wrist area. The use of a skin lotion is
recommended to solve this problem. If a red ">"
LED condition still exists, replace the wrist band.

Note: The use of skin lotions are not
recommended for use with the 3M™ 4600 Series
Thermoplastic Wrist Bands.

Rear of the 740

Template

5 feet

(1 500 mm)

 


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MO 0765-0601

VII. Shoe test

The 741 shoe electrode has to be connected to the
740 shoe jack.

Switch the 740 on. Stand on the 741 shoe
electrode. If you are using shoe straps with 1 M

resistor on both feet to be tested with the 741 shoe
electrode, you have to test the straps one after the
other, to avoid a red "<" indication. Care must be
taken not to put the non-tested foot on an ESD-
protective flooring to avoid a bypass to ground.
Depress the metal contact plate in the shoe test
area until one of the indicator LEDs is on. The
green LED indicates that the resistance of the
person through the footwear is in the range
between 750 k

Ω and the desired upper maximum

level (10, 35, 50 or 100 M

Ω). If the red ">" LED

is illuminated, clean the soles of the shoes or
check shoe grounding system (heel ground or toe
ground strap) and retest. If, after cleaning, the red
">" LED remains on, replace appropriate device.
If the red "<" LED is illuminated, the minimum
resistance of the shoes or shoe grounding system
is below 750 k

Ω.

Note: Some types of shoe grounding systems are
manufactured with a resistance of less than
750 k

Ω. These types of systems are used in

various industries such as handling of explosives
or when grounding of personnel through wrist
straps is not practical. Shoe grounding systems
with a less than 1 M

Ω resistance will indicate with

the red “<“ LED indication on the 740.

The shoe test does not influence the wrist strap
test, therefore the shoes can be tested while the
wrist strap is still connected to the 740 or the wrist
strap can be tested while the operator is standing
on the 741 shoe electrode. Both metal plates
should not be pressed at the same time.

 


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1

5

6

4

3

2

1

5

6

4

3

2

Output

connector

Output

connector

Computer

input

Computer

ground

External
voltage
source
max. 30 V

Pin 3

+ 5V

5 k

Pin 1, 2, 4 or 5

Pin 6

Relay

I max. 20 mA

Pin 1, 2, 4 or 5

Pin 6

VIII. Data Output Connector

If you are going to use the data output connector you must follow a test sequence. It must be wrist strap
test first and then the shoe test. If this sequence is not strictly kept, the output at the pins described
on page 7 will be altered.

The 740 will provide digital signals (high/low) while testing the personnel grounding devices. These
digital signals can be used for data recording (Example 1) and authorization control equipment such as
electrical door opening systems (Example 2). The output of the 740 will give you permanently +5 V at
pin 3 and DC-return at pin 6. The remaining pins 1, 2, 4 and 5 (open collector) will be high (max. +30
V / 20 mA have to be provided externally) or low (DC-return) while pressing on the contact plates
either for wrist strap or shoe tests. The chart on page 7 shows all of the possible test results and the
corresponding output levels.

Example 1: Output connection for use
with a computer

Example 2: Output connection for use
with a controlling device

 


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Data output connector pin status when testing wrist strap/shoe

The sequence for testing must be wrist strap test first and then the shoe test.

Shaded pin indicators will read "hi" if the sequence is reversed or only the shoe tests are
performed.

Data Output Connector

pin 1, 2, 4, 5

-

high or low

pin 3

-

+ 5 V

pin 6

-

DC-return

IX. Specifications

Dimension of base unit:
138 mm x 190 mm x 53 mm
(5.25 x 7.5 x 2) inches

Weight:
450 g
(15.75 oz)

Power supply:
external AC/DC transformer,
DC 24-30 V / 150 mA

Accuracy:
±10% of 2, 5, 10, 35 and 50 MΩ-ranges
±20% of 100 MΩ-range

Output:
open collector at pin 1, 2, 4, 5
(max. +30 V / 20 mA)
DC-return at pin 6, +5 V at pin 3

Measurement voltage:
DC (20

±1) V (open circuit)

 


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MO 0765-0601

740

wrist strap + shoe tester

3

<

>

o.k.

1

2

2    -
5    -

10    -
35    -

-     10
-     35
-     50
-  100

on / off

+

-

Output

R

max

DC 24

30 V / 150 mA 

750 k

A

B

X. Verification Procedure

The following procedure can be used to determine
if the 740 operates within its specifications.

Please note: The tester has no adjustable
components.

Equipment needed:

1.   resistors

-

750 k

Ω - 120 MΩ, tolerance ± 1%

2.   2 wires
as required to connect the reference resistor

Verification of wrist strap test circuit:

Connect the reference resistor to the 740 as shown
in the Figure 1. Switch the 740 unit on. Select the
2 M

Ω range and use the reference resistors as

indicated in the test table and press contact
plate A.

The LEDs will indicate as shown below if the 740
performs within specifications. Repeat this
procedure for 5, 10 and 35 M

Ω ranges.

Reference

Resistance

LED -

resistor

range settings

Indication

*750 k

2 M

Ω - range

Red

900 k

Green

1.8 M

Green

>2.2 M

Red

4.5 M

5 M

Ω - range

Green

>5.5 M

Red

9.0 M

10 M

Ω - range

Green

>11.0 M

Red

31.5 M

35 M

Ω - range

Green

>38.5 M

Red

*This example is used above

Figure 1

 


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MO 0765-0601

740

wrist strap + shoe tester

3

<

>

o.k.

1

2

2    -
5    -

10    -
35    -

-     10
-     35
-     50
-  100

on / off

+

-

Output

R

max

DC 24

30 V / 150 mA 

11.1 M

A

B

Verification of shoe test circuit:

Connect the reference resistor to the 740 as shown
in Figure 2. Select the 10 M

Ω range using the

reference resistors indicated in the test table and
press contact plate B.

The LEDs will indicate as shown below. Repeat
this procedure for 35, 50 and 100 M

Ω ranges.

Reference

Resistance

LED -

resistor

range settings

Indication

750 k

10 M

Ω - range

Red

900 k

Green

9.0 M

Green

*>11.0 M

Red

31.5 M

35 M

Ω - range

Green

>38.5 M

Red

45.0 M

50 M

Ω - range

Green

>55.0 M

Red

80.0 M

100 M

Ω - range

Green

>120.0 M

Red

*This example is used above

Figure 2

 


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x

3M 740 Wrist Strap + Shoe Tester Logbook

Example:

Not ok:

ok:

Unit calibrated on:

By:

Next calibration on:

Serial number:

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Test parameters:

Wrist Strap (W)

Shoes (S)

750 k

Ω to: 2 MΩ

750 k

Ω to: 10 MΩ

5 M

35 M

10 M

50 M

35 M

100 M

 


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MO 0765-0601

Electronic Handling & Protection Division
6801 River Place Blvd.
Austin, Tx 78726 - 9000

3

Important Notice: Before using this product, you must evaluate it and determine if it is suitable for your intended application. You assume all risks and liability associated with such use.
Warranty; Limited Remedy; Limited  Liability. This product will be free from defects in material and manufacture as of the date of purchase. 3M MAKES NO OTHER WARRANTIES INCLUDING,
BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. If this product is defective within the warranty period stated above,
your exclusive remedy shall be, at 3M's option, to replace or repair the 3M product or refund the purchase price of the 3M product. Except where prohibited by law, 3M will not be liable for any
loss or damage arising from this 3M product, whether direct, indirect, special, incidental or consequential regardless of the legal theory asserted.
Litho in USA - Recycled paper - 40% pre-consumer waste paper.

 


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