Transistor tester
Transistor testers are instruments for checking transistors and solid-state diodes.
Types of tester
There are three types of transistor testers each performing a unique operation.
- Quick-check in circuit checker
- Service type tester
- Laboratory-standard tester
In addition,Signature-pattern checkers(Curve tracers) are reliable indicators of transistors performance.
Circuit Tester
It is used to check whether a transistor which has previously been performing properly in a circuit is still operational.The transistor's ability to "Amplify" is taken as a rough index of its performance.This type of tester indicates to a technician whether the transistor is dead or still operative.The advantage of this tester is that the transistor does not be removed from the circuit.
Service type transistor testers
They usually perform three types of checks:
- Forward-current gain,or beta of transistor.
- Base-to-collector leakage current with emmiter open(ico)
- Short circuits from collector to emmiter and base.
Some service tester include a go-no go feature.
Some also provide a mean of identifying transistor elements,if these are unknown.The tester has all these features and check solid -state devices in and out of circuit. Measurements with the service type tester are relative than absolute. Even so,they are valuable to a technician in maintainingtransistorised equipement.
Laboratory-standard transistor tester or Analyser
They are used for measuring transistor parameters dynamically under operating conditions.The readings they give are absolute.Among the important charcteristics measured are
- Icbo collector current with emmiter open (Common base)
- ac beta (Common emmiter)
- Rin (Input resistance)
Transistor testers have the necessary controls and switches for making the proper voltage,current,and signal settings.A meter with acalibrated "Good"and "Bad"scale is on the front. Transistor tester are designed to check also the solid-state diodes.There are also testers for checking high transistor and rectifiers.