620UK-B Operation and Maintenance Manual – Rev J – January 2020
Page 14
13231 Rooster Springs Rd.
Austin, TX 78737
T:
(512) 858-4045
E:
amptec.com
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 620UK-B main PCB slides in easily, by following
grooves on the inside of the aluminum case.
Schematics for the 620UK-B’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 620UK-B 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
l
evel of test current. On a 1 Ω
resistor, the 620UK-B 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 620UK-B meter can be attained by
replacing the proper internal PCB. There are no serviceable components (much of the
components are surface mount) on the 620UK-B 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
620UK-B 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.
620UK-B Block Diagram
