Four-Terminal Sensing Connector | Kelvin Test

Four-Terminal Sensing Connector

Kelvin Test

Four-terminal measurement connectors are used for the accurate measurement of conductor resistance.

These connectors have a structure with two insulated contacts that are placed in touch with a single electrode to be tested. One electrode is connected to a stable current using electrical contacts, while the other uses electrical contacts or a contact probe to measure the voltage.

This test makes it possible to accurately measure a conductor's resistance without interference from the measuring instrument.


  • A custom design enables us to propose the best solution for the electrode's shape to be measured. It can be combined with various configurations of connectors such as butt contacts and fork sockets.
  • Isolated current-conducting contact and 2-pole structure for voltage measurement.
  • Stable connection due to the use of electrical contacts.
  • Accurate measurement of the resistance of a target.


  • Testing the internal resistance of large-capacity batteries
  • Inspection of the internal resistance of automotive PCUs and ECUs
  • Inspection of the internal resistance of the IGBTs

Custom solutions

We can custom-make four-terminal measurement connectors that perfectly match your requirements, such as electrode shape (including fork sockets and butt contacts), current capacity, and life span.

Case Studies

The following are examples of how our custom four-terminal measurement connectors solved our customers' problems.

Case Study 1


A customer wanted to measure only the battery’s internal resistance, but the measuring instrument also measured the instrument's resistance.


Our custom four-terminal measuring connector eliminates the instrument's resistance and only measures the battery's internal resistance.

Case Study 2


Our customer's motor's electrodes had an unusual shape, making it challenging to create a secure four-terminal connection using standard commercially available contact probes and connectors.


We manufactured a four-terminal contactor to fit the motor's electrode shapes, allowing it to be connected to measure its internal resistance.

Case Study 3


When using a standard commercially available four-terminal contact probe to perform measurements. However, it didn't fit the product's electrodes well, resulting in scratching, thereby making the product unsellable.


We provided a four-terminal connector specially designed using coil springs as contacts to avoid scratching the product. The product remained in pristine condition, thereby making a great impression on buyers and protecting the maker's reputation.



A customer wished to measure the internal resistance of their product. We designed a two-pole connector to match the product's electrodes. It combines isolated current-carrying contacts and voltage measurements. We can custom-make various connector shapes such as butt contacts and fork sockets.

Fork Sockets for ECU Testing

  • Current Application: Contact band 25 A
  • Voltage Measurement: Contact band
  • Workpiece Shape: Bus bar for product connectors
  • Inspection Connectors: Designed to match the product connectors of automotive ECUs

Butt Contacts for Battery Inspection

  • Current Conduction: Coil spring contact 360 A
  • Voltage Measurement: Contact probes
  • Workpiece Shape: .551" (14mm) square planar terminals
  • Testing Connector: Pressed against the battery's flat terminal

Butt Contacts for IGBT Inspection

  • Current Application: Coil spring contact 200 A
  • Voltage Measurement: Contact probes
  • Workpiece Shape: M6 hole terminal block
  • Contact Probe: Custom-made to press against the M6 hole's edge

Sockets for Capacitor Testing

  • Current Conduction: Coil spring contact 100 A
  • Voltage Measurement: Contact probes
  • Workpiece Shape: .354" (9 mm) diameter short plug
  • Advantage: Compact design, allowing for a stable connection to short plugs