Product Jul. 01, 2014

Hioki Launches Insulation Tester ST5520

Instrument Delivers Industry’s Fastest Testing Time

Nagano, Japan

Hioki E.E. Corporation is pleased to announce the launch of the Insulation Tester ST5520.

In order to ensure the safety of electronic components such as relays and connectors and of lithium-ion and other batteries used in electric vehicles and smartphones, it is necessary to qualify their insulation characteristics, and testing system manufacturers vie to offer instruments capable of high-volume, high-speed testing.

The Hioki ST5520 Insulation Tester speeds this process by delivering the industry’s fastest testing time at 50 ms (0.05 sec.). Moreover, it provides a contact check function to prevent inadvertent shipment of defective parts in the event the instrument suffers a break in a measurement line or faulty contact with the object under test. The ST5520 also allows the test voltage to be set in 1 V increments from 25 V to 1,000 V to ensure compatibility with various manufacturers’ test processes.

Development Background
Since a failure to adequately insulate electronic components or lithium-ion or other batteries could result in a short or electric shock, it is necessary to verify safety as part of the production process.

Currently, it is critical for manufacturers that mass-produce these devices to be able to measure extremely large quantities of parts quickly. Hioki’s goal was to develop an instrument that would deliver the industry’s fastest testing time in order to accommodate this need, and with the ST5520 it has achieved that goal.

Principal Application
Insulation testing on production lines used to manufacturer electronic components and lithium-ion and other batteries

Product Features
1. Faster testing thanks to the industry’s fastest measurement speed
With testing times as fast as 50 ms (0.05 sec.), the ST5520 delivers the fastest performance in the industry. A full 10 times faster than Hioki’s previous legacy product (Model 3154), whose fastest testing time was 500 ms (0.5 sec.), the new insulation resistance meter can shave valuable time from customers’ test processes.

2. Contact check function to improve test quality by preventing shipment of defective parts
Were a measurement line to break or the instrument to experience faulty contact with the object under test while a test is in progress, defective products could be inadvertently shipped to market. To prevent this eventuality, the ST5520 comes standard with a contact check function that notifies the operator in the event of a measurement line break or faulty contact. In this way, the instrument helps improve test quality.

3. Operator-configurable output voltage from 25 V to 1,000 V in 1 V increments
The insulation resistance measurement process involves applying a test voltage to the object under test. There is no specific test voltage commonly established for insulation testing of lithium-ion and other batteries, so the test voltage varies by manufacturer. Additionally, test voltages used for electronic components such as relays and connectors are expected to change over time to accommodate evolving standards. Consequently, Hioki made the test voltage operator-configurable from 25 V to 1,000 V in 1 V increments.

4. Verification of external I/O signals on the instrument’s screen
On production lines where large quantities of parts are tested, measuring instruments are automatically controlled using external I/O signals. In response to customers’ need to be able to check whether these signals are being properly input and output at a glance, Hioki designed the ST5520 with functionality that enables operators to check the I/O status of these signals on its screen.



Established in 1935, HIOKI E.E. CORPORATION (TSE: 6866) has grown to become a world leader in providing consistent delivery of test and measuring instruments through advanced design, manufacturing, and sales and services. By offering over 200 main products characterized by safety and quality while meeting an expansive range of applications, we aim to contribute to the efficiency and value of our customers' work in research and development, production and electrical maintenance. HIOKI products and services are available around the world through our extensive network of subsidiaries and distributors. Information about HIOKI is available at

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ST5520 Insulation Resistance Tester