The 620ES Tester measurement circuitry is also
failsafe current limited, even under worst case
component failure.
A simple startup test
procedure which also has the 620ES Tester
user perform a functional check using the
optional "FTB-620ES" Functional test box
with milliammeter would also detect any
current level even getting close to the Failsafe
level.
For the 620ES Tester the normal or typical
operating current level is less than 10 mA, and
<15mA on as a Failsafe Level
.
E-7 . Ultra-Safe Power Supply Scheme
The +5 volt power supply is provided directly
by the batteries (for driving the LED displays
and digital logic). The ±5VD is used for driving
IC8, the low battery detection circuit. The ±15V
power supply is generated by IC7 for the digital
voltmeter (DVM) chip set (IC1 and IC2).
The ±5 VA is developed by one DC to DC
convertor circuitry: composed of Q103,Q104,
T102, D103, D104, IC102 for the negative
polarity. The other DC/DC convertor is
composed is composed of Q101, Q102, T101,
D101, D102 and IC101 for the positive polarity.
8
A
B
G
F
C
E
D
D.P.
SEGMENT PIN
A . . . . . . . . 1
B . . . . . . . . 13
C . . . . . . . . 10
D . . . . . . . . 8
E . . . . . . . . 7
F . . . . . . . . 2
G . . . . . . . . 11
D.P. . . . . . . . . 6
Common . . . . 14
8
PIN
1
2
3
4
5
6
7
PIN
14
13
12
11
10
9
8
Figure E4
- 620 series LED Display Pin Out Detail/Functions
