Shorted Turns Tester for Bobbin Wound Coils

Key Features :

The STT-4 Shorted Turns Tester offers a quick and easy means to detect shorted turns in bobbin coils. It is a non-stress and non-contact test. By placing a coil over the test probe, shorted turns will inductively couple with the probe field and load the STT-4 circuit. If there is no current path within the coil, there is no coupling.

The STT-4 is easy to set-up and to use. The tester can be used without coil standards in most cases although sample loops of typical coil diameters and wire sizes are helpful for set-up. An analog panel meter is provided to help the operator determine the amount of coupling and to set the Go/No-Go limits.

On/Off and Limit Adjust are front panel controls. The limit adjust allows the user to set the trigger point for the Go / No-Go Indicators. Red and Green LED’s and an Audio Buzzer provide signals for the operator. An optional relay output can be supplied for automated applications.

The STT-4 offers a very sensitive and accurate test, yet it is a rugged and reliable instrument. It can deduct a single shorted turn of wire as small as #55 AWG (014 mm) In general the test is independent of the number of turns in the coil. Because of the simplicity, speed and reliability of its operation, the STT-4 can detect errors early in the coil assembly process and help to prevent work on bed parts.


Standard Probe Types for the STT-4 Shorted Turns Tester

The STT-4 Shorted Turns Tester is designed to operate with any of the following standard probe sizes:

Type Diameter And Height Part Number

High Wear

Min. ID: (1/16”) 1.7 mm
Max. OD: (2”) 50.8 mm
Max Height: (1-1/2”) 38.1 mm



High Wear and High Sensitivity

Min. ID: (3/32”) 2.5 mm
Max. OD: (2 1/2”) 65 mm
Max Height: (1-3/4”) 45 mm



Hand Held High Sensitivity

Min. ID: (3/16”) 5 mm
Max. OD: (6”) 150 mm
Max Height: (2 ½”) 60 mm



Sensing Coils

Min. ID: (1 ½”) 38 mm
Max. OD: (7”) 175 mm
Max Height: (5”) 125 mm



Slot Sensor

Min. ID: (2 ½”) 64 mm
Max. OD: (8”) 200 mm
Max Height: (7”) 175  mm



Probes length should be at least 1.5 times the OD of the coils to be tested. Please note that the above probe sizes are approximate. Other sizes can be made to order. Please inquire.