Wrist Strap Tester Calibration

A wrist strap tester easily, quickly, and accurately measures the resistance between an operator and the ground cord. It is available both as a wall-mounted version and a portable version that is easy to transport to test that operators are properly grounded. A wrist strap tester verifies that the electrostatic discharge protection is sufficient by measuring the resistance between an operator’s hand and the ground.

The portable version is battery-powered with only a low test voltage of 9VDC which is sufficient without using high amounts of power. Typically the portable version indicates that a continuous grounding path exists between a wrist band and coil cord by displaying three levels of resistance: A high resistance level, a low resistance, and a pass level. This is indicated by color LED lights and an audible alarm. Test parameters are set in the factory to pass the test between 800K ohms and10M ohms.

The wall-mounted version can check, the heel strap resistance is set at between 750K ohms and 35M ohms which meets the EN IEC 61340 specifications.

Wrist Strap Testers are designed to provide a quick and simple means of testing both wrist straps and footwear before entering an electrostatic discharge protected area and are designed to measure both high and low fail and pass functions. Testing is achieved by placing the jack-plug into the socket and wearing the wristband and touching the metallic test-plate upon which the status of the wristband is indicated. An audible tone sounds to warn of its failure. This is useful for grounding products designed to control static electricity for the protection of electronics.

 

Description

If the user wears the wrist strap and plugs the coiled cord into the tester and then touches the metallic plate on the tester then an electrical circuit is completed through the wrist of the wearer from the ground back to the tester. The device indicates if the resistance is within acceptable limits or not.

Being a portable battery-powered device, it is perfect for small labs for a supervisor to spot-check workers and ensures regulatory compliance which requires that when personnel are working at workstations, they remain connected to the ground via a wrist strap system.

A compliance verification plan is established to ensure the organization’s fulfillment of this requirement. Compliance verification records are maintained to provide evidence of conformity to the technical requirements. The test equipment is selected that is capable of making the measurements defined in the compliance verification plan.

 

Test Procedure

A wrist strap is worn by the operator and the cord is plugged into the banana jack. When the operator touches the test plate, the green LED will light up if the operator-to-ground resistance is between 800K and 10M ohms. If the resistance is below 800K, the red Low LED will light, and to indicate low resistance the alarm will sound. If the resistance is above 10M Ohms, the red High LED will light and the alarm will sound.

Dry skin may be one of the reasons that the resistance may be indicated as too high. This issue can be resolved by applying some conductive moisturizing lotion on the wrist and repeating the test. The moisturizing lotion should be compatible with the process requirements. If even after applying the lotion, the test still fails, the operator should notify their immediate supervisor.

This tester is used to ensure that the single-wire wrist straps comply without workers ever leaving their stations. Just plugging the wrist strap cord into the banana jack while wearing the wrist strap and touching the metallic test button will complete the test.

 

Calibration

We recommend annual calibration of wrist strap tester with NIST traceable standards. Calibration is done to ensure that the device is working within the specifications.

The following resistance should give the display shown:

 

Calibration Procedure

Connect the test resistance from the banana jack to the test button. With resistance applied and the test button pressed, the display should give 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.

The testing of the wrist strap covers the resistance of the cord, the resistor, the connector, the resistance of the interface of the cuff, and the resistance of the person. Normally the maximum acceptable resistance most often used for wrist strap grounding is between 10M ohms and 750K ohms.

 

e2b calibration provides reliable and cost-effective calibration services for your wrist strap testers. Our verifiable and traceable services are unmatched in the industry.  We are ISO-17025: 2017 compliant and registered with ANAB. We are also ANSI/NCSL Z540-1-1994 certified. We are NIST Traceable Wide scope of ISO/IEC 17025 accreditation. Please contact e2b calibration for more information about our on-site calibration services.

 

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