Amptec Research 620LK 설치, 운영 및 유지보수 매뉴얼 - 페이지 14

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620LK Operation and Maintenance Manual – Rev. J – Updated January 2020

The DVM PCB's electronics use a high input impedance voltage sense circuit. This

circuit draws very little current, while measuring the DC voltage drop across the

resistance under test. The AMPTEC 620LK main PCB slides in easily, by following

grooves on the inside of the aluminum case.

Schematics for the 620LK's PCB are protected and strictly confidential, regardless of

the circumstance.

E-4 Block Diagram and Circuit Description

E-5 Principle of Operation

Using Ohm's Law (V/I =R), the AMPTEC 620LK Bond Meter first outputs constant DC

current through a given test resistance, then measures the voltage drop across it while

scaling its display as resistance. The 1.9999 Ω range outputs a constant 100 mA DC

level of test current. On a 1 Ω resistor, the 620LK 100mA output should get a 100mV

drop (0.10V/0.10A). For DVM scaling on the 2 Ω range, voltage drop is amplified using a

x10 (for range scaling), hence a 10 mV drop becomes 100mV. This DVM input is

displayed as 100.00 m Ω on a 0.100 Ω std. During the cycle, the meter changes

polarity, samples again, and displays the average reading of both polarities.

E-6 PCB Troubleshooting and Diagnostic Testing

If the malfunction is a faulty part, the repair of the 620LK meter can be attained by

replacing the proper internal PCB. There are no serviceable components (much of the

components are surface mount) on the 620LK PCBs, so it is often a case of entire PCB

replacement. See section E-2 on page 13 for more information about sending your

product in for repair.

The following sub-sections will facilitate the diagnosis as to whether the AMPTEC

620LK current source circuitry or digital voltmeter circuitry needs repair or replacement.

These steps should only be performed by authorized personnel who are trained to do

so.

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