Fluke Biomedical 960SG-500 - Manual (Page 12)

Theory of Operation
4
4-2
Table 4-1. Example of Binary Outputs To U6
Selector Switch
U8 Input *U8 Output
(Low True) U6 Input
1 1
A 0
A 1
2 1
B 1
B 0
3 1
C 0
C 1
4 1
D 1
Not Used
5 0
6 1
7 1
8 1
9 1
*Low true equivalent to “5”
1 = High (+5)
0 = Low (GND)
4.3 Pulse Height Circuitry
Potentiometer R24 is preset to provide a 2V amplitude pulse at the output jack. U11 functions as a unity gain voltage
follower.
4.4 Preset Circuitry
The output from U5 is fed to U9, which permits the pulse to be selected either as a fixed 2V pulse or as a variable
amplitude pulse. The selected preset pulse out of U9 is AC coupled via capacitor C24 and a DC restoration circuit to
U10. The DC restoration circuit is comprised of CR1, CR2, and associated components. The signal is fed to U10 where
the output polarity is switch selected. The signal from U10 goes to U12; the Op Amp that actually provides the signal
polarity change. From U12 the pulse signal is fed to U13. Potentiometer R19 is a gain adjustment. Current driver U13
feeds the pulse to the BNC signal output jack on the front panel. The circuit output is a gain adjusted 800 ns pulse at
the appropriate frequency.
4.5 Output Circuitry
The preset pulse is AC coupled via C24 with a DC restoration circuit comprised of CR1, CR2 and associated
components, to U12. Current driver U13 provides the pulse to the BNC jack on the front panel. R19 is a gain
adjustment for the output circuit.
4.6 Power Supply