What is an ESD tester?

ESD（Electrostatic discharge) tester, also called ESD combo tester and ESD checker, is used to measures the resistance of personal grounding devices includes ESD strap straps and ESD footwear.

Working principle of ESD tester

The working principle of an ESD tester involves creating a circuit between the static dissipative shoes worn by the operator and the ESD testing footplate. When the operator steps on the footplate and touches the test button, this circuit is formed. The ESD tester measures the resistance of this circuit to ensure that it falls within a specified range.

The ESD Defender tester measures the resistance of the left shoe (similarly for the right foot) by charging the left footplate and setting the test button and the right footplate to ground. This setup generates currents I1 and I2.

This measurement can effectively verify the grounding pathway of the ESD footwear and whether the resistance meets the relevant ESD standards.The testing of wrist straps operates on a similar principle, ensuring the safe discharge of static electricity to prevent damage to sensitive electronic components.

Why we need an ESD test?

Electrostatic charges are commonly generated on everyday materials such as synthetic fibers in clothing, hair, and shoes with rubber soles. These charges may lead to significant damage to sensitive electronic components and assemblies. ESD testing ensures all personnel devices properly grounded before entering, which is essential in preventing the accumulation and transfer of static charges.

How to pass ESD testing?

To ensure compliance with ESD (Electrostatic Discharge) standards, such as ANSI/ESD S20.20 and IEC61340-5-1 standards, the electronics manufacturing facilities must conduct varied ESD testing. This testing encompasses a multitude of specific scenarios including personnel grounding device testing, flooring ESD testing, mat ESD testing, workstation ESD testing, and packaging ESD testing, among others.

We are talking about ESD testing of personnel grounding device here. ESD tester, aka ESD combo tester, is designed to be quickly and accurately conduct such testing. To ensure successful testing, the following preparation steps are necessary:

• Install and configure the ESD tester according to user manual and industry standards
• Put on personnel gounding deivces (wrist band, ESD shoes/ESD grounder) properly
• Stand on the ESD footplate and press the test button initiate the test
• Observe the indicator lights or display on the tester, a green light indicates a pass, while a red light indicates a fail.

Types of ESD Tester

There are various types of ESD testers based on testing methods and management systems.

–ESD Wrist Strap Tester are designed to check the functionality of anti-static wrist straps. They ensure that the wrist straps are correctly grounding the static electricity that accumulates on a person’s body.

–ESD Footwear Tester are used to verify that ESD-safe footwear is functioning properly. Footwear helps in safely discharging the static electricity into the ground.

–ESD Combo Tester are versatile devices that can test multiple types of ESD protection equipment, including wrist straps, footwear, and garment. These testers provide a thorough assessment of the ESD safety measures in place.

-Offline ESD Tester: quickly measure resistance values without connection to a computer. They are cost-effective and useful for enviroments where data logoing is not required.

-Networked ESD Tester: capable of connecting to a database to store test data alongside employee IDs. This functionality aids in automated record-keeping and tracking, enhancing monitoring compliance.

How often should ESD wrist straps be tested?

The ESD wrist strap is used for eliminating static electricity from the human body. It is commonly used in manual operations on workbenches. By grounding the plate clip, the static electricity accumulated in the human body can be discharged to the ground, achieving elimination.

Over time, the ESD wrist strap can wear out and accumulate dirt, reducing its effectiveness. To ensure it continues to work properly, it’s important to regularly test the ESD wrist strap with an ESD wrist strap tester. ESD wrist straps should be tested daily to ensure proper functioning specially in environments where strict ESD control is crucial, such as in electronics manufacturing or repair.

How to test ESD wrist strap?

ESD wrist strap tester is used to assess the proper functioning of ESD wrist straps. The specific steps are as follows:

1. Secure the ESD wrist strap on your wrist ensuring the metal plate is in close contact with your skin.
2. Insert the grounding cord of the wrist strap into the designated socket on the tester, and simultaneously press the test button with your finger until the test completes.
3. Observe the test results displayed by the tester.

ESD Defender tester will provide a numerical value and use red and green indicators to show whether the test has passed or failed:
Red (High) light: Fail, test value ≤ 750KΩ
Red (Low) light: Fail, test value ≥10MΩ
Green light: Pass, 750KΩ≤test value≤10MΩ

Whether the measurement results meet the conditions specified by EPA can be determined by referring to the following standards:

IEC 61340-5-1: The international certification standard for electrostatic control, published by the International Electrotechnical Commission (IEC).

ANSI/ESD S20.20: The American national standard for the protection of electrical and electronic parts, assemblies and equipment (excluding electrically initiated explosive devices), published by the ESD Association.

SJ/T10694-2006: The general specification for electrostatic discharge testing in the manufacturing and application systems of electronic products, published in China.

GJB 3007A-2009: The military standard of the People’s Republic of China for electrostatic discharge control.

How to test esd heel straps?

An ESD footwear tester  offers a way to assess the grounding performance of ESD heel straps. The specific steps are as follows:

1. Inspect the heel strap:
   • Visually check the heel strap for any signs of damage, cracks, or wear.
   • Ensure the conductive material is not compromised.
2. Measure the resistance:
   • Put on the heel strap and stand on footplate of ESD Defender.
   • Place and hold the finger on the test button to activate the test.
3. Check the resistance value:
   • The resistance will be displayed on the ESD Defender Monitor, which should fall within the recommended range, typically between 750k to 35 megohms.
   • If the resistance is outside this range, the heel strap may need to be replaced.
4. Document the test results:
   • Record the resistance value and any observations about the heel strap’s condition.
   • Maintain a log of the test results for future reference and compliance purposes.

Regular testing and proper maintenance of ESD heel straps are essential to ensure the effectiveness of your ESD control program and to protect sensitive electronic components from electrostatic discharge.

How to calibrate esd tester?

Industry standards and regulations, such as ANSI/ESD S20.20 and IEC 61340-5-1, require that ESD testers be calibrated at least annually to ensure the reliability of the measurements.

The ED311 Periodic Calibration Tool allows users to conduct calibraiton on ESD Defender testers by themselves on the shop floor within a few minutes, avoiding downtime and high calibriation costs charged by third-party labs.

Click here to check out the video tutorial of calibration for ESD Defender Combo Tester G4. Or contact ESD Defender Consultant for further support.