3M 740 Manuale utente

1 / 11

MO 0688-1101

740

wrist strap + shoe tester

o.k.

740 Wrist strap + shoe tester

Operating Instructions MO 0688-1101

Nov 2001

2 / 11 MO 0688-1101

740

wrist strap + shoe tester

o.k.

MΩMΩ

2 -

5 -

10 -

35 -

- 10

- 35

- 50

- 100

on / off

Output

max

DC 24

•

30 V / 150 mA

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.

I. General

Personnel grounding devices such as wrist straps

and conductive footwear are the primary method

to minimise 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

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»

3 / 11

MO 0688-1101

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 kΩis 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 kΩ. 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:

-3.5" - diskette containing instruction manual and

740 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 electrodes type 741 (single electrode) or

741D (dual electrode) (to be ordered 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 741/741D shoe electrode must be connected

if footwear testing is required.

4 / 11 MO 0688-1101

V. Wall Mounting

The enclosed 3M Dual Lock™fastening discs

must be screwed to the wall using the attached

template approximately 1500 mm (5 feet) above

the floor. Drill three holes of 5mm (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 kΩto the upper selected value of 2, 5, 10 or

35 MΩ. If a red "< "-LED is on, 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.

Rear of the 740

Template

1 500 mm

(5 feet)

If the green LED illuminates

now, the ground cord can be

used.

If the red "> "-LED is lit,

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.

5 / 11

MO 0688-1101

VII. Shoe test

Either the 741/741D shoe electrode must be

connected to the 740 shoe jack.

a) when the 741 single shoe electrode is

used:

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 lit, replace it

by an appropriate device. If the red "< "-LED is

illuminated, the minimum resistance of the shoes

or shoe grounding system is under 750 kΩ.

An electrical hazard to personnel may exist at the

work place.

b) when the 741D dual shoe electrode is

used:

The dual shoe electrode allows differentiation

between the right and left shoe; giving the right

shoe a preference in indication. This means, if

both shoes or just the right one are out of range,

you will get identical indications as it would be

with the single shoe electrode. If just the left shoe

is out of range, the corresponding red LED will

flash. Consequently, in case of a steadily lit red

LED, you shall clean or remove right shoe first

and retest. If the right shoe is in the "ok"-range

then, you will obtain information about

performance of the left shoe and you can react

accordingly.

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 shall

not be pressed at the same time.

Switch the 740 on. Stand on the applied shoe

electrode. If you are using shoe straps with a

1MΩ- 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 "too low" -

indication. Care must be taken not to put the non-

tested foot on ESD - protective flooring to avoid a

bypass to ground. Depress the metal contact plate

for shoe test until one of the indicator - LEDs

lights up. The green LED indicates that the

resistance of the person through the footwear is in

the range between 750 kΩand the desired upper

maximum level (10, 35, 50 or 100 MΩ).

6 / 11 MO 0688-1101

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 mixed up.

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 authorisation 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

Output

connector

Output

connector

Computer

input

Computer

ground

External

voltage

source

max. 30 V

Pin 3

+ 5V

5 kΩ

Pin 1, 2, 4 or 5

Pin 6

Relay

I max. 20 mA

Pin 1, 2, 4 or 5

Pin 6

7 / 11

MO 0688-1101

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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8 / 11 MO 0688-1101

740

wrist strap + shoe tester

o.k.

2 -

5 -

10 -

35 -

- 10

- 35

- 50

- 100

on / off

Output

max

DC 24

•

30 V / 150 mA

750 kΩ





X. Calibration 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 kΩ- 120 MΩ, tolerance ±1%

2. 2 leads

as required to connect the reference resistor

a) calibration of wrist strap test circuit:

Connect the reference resistor to the 740 as shown

in the figure below. Switch the 740 unit on. Select

the 2 MΩ-range and use the reference resistors as

indicated in the test table and press contact

plate A.

b) calibration of shoe test circuits:

The 740 Tester can either operate with the single

or dual shoe electrode. They are identified by the

wiring in the 3-pin plug according to DIN 41 524,

type HIRSCHMANN MAS 3100, that connects

the shoe electrode to the 740. For the single shoe

electrode, the cord is connected to pin 1 while

pins 2 and 3 are shunted and grounded.

The dual shoe electrode uses the same plug but

has got the following connections:

pin 1: right shoe electrode

pin 2: open

pin 3: left shoe electrode.

Reference Resistance LED -

resistor range settings Indication

*750 kΩ2 MΩ- range Red

900 kΩGreen

1.8 MΩGreen

>2.2 MΩRed

4.5 MΩ5 MΩ- range Green

>5.5 MΩRed

9.0 MΩ10 MΩ- range Green

>11.0 MΩRed

31.5 MΩ35 MΩ- range Green

>38.5 MΩRed

*This example is used above

The LEDs will indicate as shown below if the 740

performs within specifications. Repeat this

procedure for 5, 10 and 35 MΩ-ranges.

9 / 11

MO 0688-1101

740

wrist strap + shoe tester

o.k.

2 -

5 -

10 -

35 -

- 10

- 35

- 50

- 100

on / off

Output

max

DC 24

•

30 V / 150 mA

11.1 MΩ

II) calibration of the dual shoe test circuits:

The 740 Tester measures the resistance of both

shoes almost at the same time. The test result for

the circuit of the right shoe has got priority. The

calibration can be either performed with two

reference resistors for both circuits to be checked

at the same time or -corresponding to the single

shoe test - with one reference resistor for one

circuit to be checked and an appropriate bridge

resistor (1MΩe.g.) for the other circuit. For

completion of calibration, the test has to be

repeated with connections of the resistors vice

versa. Follow the instructions for the single

electrode calibration test accordingly.

For the operation with two reference resistors

proceed as follows: Connect one reference resistor

between contact 1 of the socket and the stud and

the other one between contacts 2 and 3. Select the

10 MΩ-range and set the reference resistors as

indicated in the test table and press contact

plate B. The LEDs shall light as shown below.

Repeat this procedure for 35, 50 and 100 MΩ-

ranges.

Right shoe Left shoe

electrode electrode

circuit circuit Signal

OK OK green steadily

high OK > red steadily

low OK < red steadily

OK high > red flashing

OK low < red flashing

high low > red steadily

low high < red steadily

high high > red steadily

low low < red steadily

I) calibration of the single shoe test circuit:

Connect a reference resistor to the 740 between

contact 1 of the socket and the stud as shown

below. Contacts 2 and 3 of the socket shall be

bridged via an appropriate resistor (1MΩe.g.)

Select the 10 MΩ-range and set the reference

resistors as indicated in the test table and press

contact plate B.

The LEDs shall light as shown below. Repeat this

procedure for 35, 50 and 100 MΩ-ranges.

Reference Resistance LED -

resistor range settings Indication

750 kΩ10 MΩ- range Red

900 kΩGreen

9,0 MΩGreen

*> 11,0 MΩRed

31,5 MΩ35 MΩ- range Green

>38,5 MΩRed

45,0 MΩ50 MΩ- range Green

> 55,0 MΩRed

80,0 MΩ100 MΩ- range Green

> 120,0 MΩRed

*This example is used above

10 / 11 MO 0688-1101

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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 kΩto: 2 MΩ750 kΩto: 10 MΩ

5 MΩ35 MΩ

10 MΩ50 MΩ

35 MΩ100 MΩ

Altri manuali per 740

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