F9 Fetal & maternal Monitor Service Manual Principle Introduction
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F1 and F2 are two containers for fuses containing, the specification of the fuse is: 1.6A 250V.
J1 is the equipotential grounding point that connects to the ground.
J2 is a 3-pin socket for outer power input.
J3 is input connects to the PS800B module in the machine.
C1, C2, C3 and C4 are Y capacitors, every capacitor resists 2300V voltage. Connecting a 10
Ω
resistor and two Y capacitors in series between L-PE and N-PE will improve the fetal heart and
data jumping problem when measuring FH with EFT.
When laying out the PCB of this board, the creepage distance between L, N and PE must not less
than 8mm, the distance between L and N must not less than 3mm.
7.2.6 Key Board
The key board codes the operation of keys and control knob with AT89C2051 singlechip
processor, sends keycode to main control board with PS2 protocol, answers for corresponded
keys and controls display of power indicator, AC indicator and Charge indicator. Its structure
block diagram is as follows:
Figure 7-5 Key board principle block diagram
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