Industry’s Fastest Insulation Tester Assesses in as Fast as 50ms

SKU: ST5520 Category:


The Hioki electrical safety testers are designed for insulation resistance and voltage withstand testing of electrical devices and components according to various safety standards. The ST5520 is the fastest insulation tester in the industry, delivering pass/fail assessment in as fast as 50 ms. 25 to 1000 V test voltage with 1 V resolution.

Key Features
• Rapidly assess in as fast as 50 ms
• Quick discharge of residual voltage
• Freely configurable test voltage (set from 25 V to 1000 V, 1 V resolution)
• Contact check function (prevents errors due to poor contact)
• Short-circuit check function (stops potential defects from reaching the market)
• Ideal for battery production lines

Model No. (Order Code)

ST5520 with external I/O output
ST5520-01 with BCD output

Note: The ST5520 and ST5520-01 cannot be operated alone. Please select and purchase the optional test leads to accommodate your application.



High Speed, Reliable, Advanced

The Insulation tester ST5520 is everything you need for accurate measurement.



Industry’s Fastest Testing Speed

The Insulation Tester ST5520 delivers the fastest insulation resistance testing in the industry, meeting all the requirements of production lines thanks to rapid takt times.

Rapidly assess in as fast as 50 ms

Testing is complete in as little as 50 ms — the fastest time in the industry. This is 700 ms faster than legacy Hioki models.

Quickly discharge residual voltage

The post-test residual voltage discharge time has been reduced significantly compared with legacy models. As a result, when comparing an identical sample under the following conditions, a takt time improvement of 990 ms is estimated.

Prevents errors due to poor contact

The contact check function allows you to check that proper contact has been made with the device under test prior to the testing. This ensures that resistance testing is not carried out without proper contact, as this can result in erroneous assessment. There are two methods: 4-wire contact check and comparator contact check.

Stops potential defects from reaching the market

With this function, a low voltage (2 V to 4 V DC) is applied to the test patterns to check for micro-shorting prior to insulation testing.

Safe, easy operation at your fingertips

The use of optional Switched Probe 9299 lets you to operate the ST5520 while holding the probe.

Basic specifications (Accuracy guaranteed for 1 year, Post-adjustment accuracy guaranteed for 1 year)

Measurement items Insulation resistance (Applied DC voltage method)
Testing voltage (Measurement range: AUTO/MANUAL setting is possible)
25 V ≤ V < 100 V (2.000/20.00/200.0 MΩ),
100 V ≤ V < 500 V (2.000/20.00/200.0/2000 MΩ),
500 V ≤ V ≤ 1000 V (2.000/20.00/200.0/4000 MΩ)
Basic accuracy ±2 % rdg. ±5 dgt.
25 V ≤ V < 100 V [0 to 20 MΩ]
100 V ≤ V < 500 V [0 to 20 MΩ]
500 V ≤ V ≤ 1000 V [0 to 20 MΩ]
Measurement speed Fast: 30 ms/time, Slow: 500 ms/time (selectable)
Display LCD (service life: 100,000 hours), 4-level backlight
Internal memory Saved items: rated measurement voltage, comparator upper limit /lower limit values, test mode, beep sound to distinguish the result, test time, response time, resistance range, measurement speed
Memory capacity: up to 10 items (can be saved/loaded)
Comparator setting UPPER_FAIL: Measured value ≥ upper limit value
PASS: Upper limit value > measured value > lower limit value
LOWER_FAIL: Measured value ≤ lower limit value
Judgement process Beep sound, PASS / U.FAIL/L. FAIL: light up on LED display, When UL_FAIL, U.FAIL / L.FAIL light up simultaneously, EXT.I/O output, judgement result can be obtained via RS-232C
Test duration Definition of test duration: Test duration = Response time + Measurement time
Function: Set the time from voltage application until pass/fail assessment
Configuration range: 0.045 s to 999.999 s (0.001 s resolution)
Response time timer After the start of the test, comparator judgment operation can be prohibited until a set interval from 0.005 sec. to 999.999 sec. (at 0.001 sec. resolution) has passed.
Analog output DC +4 V f.s.
Interface RS-232C (standard), External I/O (External control input, Judgment result)
BCD output (ST5520-01 only)
Power supply 100 to 240 V AC, 50/60 Hz, 25 VA max.
Dimensions and mass 215 mm (8.46 in)W × 80 mm (3.15 in)H × 166 mm (6.54 in)D, 1.1 kg (38.8 oz)
Accessories Instruction Manual ×1, Power cord ×1, EXT. I/O Connector ×1, Connector Cover ×1



INSULATION / WITHSTANDING Test Instrument series

Catalog: Motor Measurement Applications

Measuring Instruments for the Battery Industry

User Guides

Insulation Tester ST5520/ST5520-01 Programming Command Compatibility with 3154

Technical Notes

Insulation Tester ST5520

Declaration of Conformity



Input cable (G)

* For the MR8990 *Voltage is limited to the specifications of the input modules in use.



70 cm (2.30ft) length, detachable large alligator clips or needle tips are bundled, CAT IV 600V, CAT III 1000V

Input/Output cords

Note: Effect of cable parasitic component
Response waveform changes according to cable length. For consultation on special order products with cable capacity within a certain range, please contact your Hioki distributor.



80 cm (2.62 ft) length


1.2 m (3.94 ft) length

Leak Current

*For commercial power lines, 50/60 Hz



3.5 mm (0.14 in) dia. mini plug to banana, 1.5 m (4.92 ft) length


3.5 mm (0.14 in) dia. mini plug to banana, 1.5 m (4.92 ft) length

Other options for Input



Receiving side banana, output BNC terminal

PC communication

*The 9151-02 is only for the RM3545-01


RS-232C CABLE 9637

For the PC, 9 pin - 9 pin, cross, 1.8 m (5.91 ft) length

Insulation Resistance Measurement of Lithium-ion Secondary Batteries 

Application Notes FA1240-6x (English)

Drivers, Firmware, Software