Note

Since U512 pin 2 is at a virtual ground (currents

are being summed at this

 

node), voltage levels at this point are difficult to

interpret.

 

 

 

Ramp Counter

See function block D of A3 Interface Assembly Schematic Diagram (sheet 2 of 6).

The ramp counter is used for non-zero-span sweeps and for zero-span sweep times greater than 30 ms. The analog sweep ramp is compared to the digital ramp counter. When the analog sweep ramp exceeds the DAC output generated for that ramp counter setting, HRAMP-COMP toggles high, indicating the end of a bucket. The ramp counter counts horizontal buckets. There are 600 buckets per sweep, so the ramp (bucket) counter counts from 0 to 600. The ramp counter is incremented by HRST-PK-ENA.

1. Press [w) on the HP 8560A and set the controls as follows:

SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lMHz DETECTOR MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE

2.For sweep times between 100 ms and 60 s, HODD (A3U525 pin 3) is a square wave with a period defined by (2 x sweep time/600). For example, for a 6 s sweep time, HODD has a period of 20 ms. The ramp (bucket) counter will be odd every other bucket.

ADC/lnterface Section 7-25