4.1. Before test
Some rules must be followed before fault detection.
• The PCB to be measured must be powered off.
• Make sure that the capacitors on the PCB are discharged. Higher than 24V charged capacitors may
damage the device. Otherwise, the product will be out of warranty.
4.2. Theory
The device works by applying a current-limited AC signal across two points of a component. The current
flow causes a vertical trace deflection, while the applied voltage causes a horizontal deflection. Together
they form a unique V-I signature that represents the overall health of the device under test.
The signature of all analog components is a combination of one or more of the four basic signatures:
resistance, capacitance, inductance, and semiconductor. Each of these components reacts differently to the
applied AC test signal. For this reason, recognizing the four basic signatures on the oscilloscope display is a
key to understanding analog signature analysis.
Figure 6. Component characteristics in XY mode (horizontal trace voltage, vertical trace current)
UCE-DSO4200C is designed to diagnose the failures in all types of electronic circuit boards. The product is
provided with two channels and allows the comparison of the defective boards with the intact boards. All
V-I impedance curves consist of 12-bit 256 different measurements per channel.
The following components can be tested with this device.
Passive components: resistance, capacitor, coil
Diodes: general purpose, zener, varistor
Transistor: NPN, PNP, bipolar, Darlington, JFET, MOSFET, UJT
Triggered components: SCR, TRIAC, relay
Optoelectronics: LED, photo-transistor, optocoupler
Integrated circuits: digital, analog
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