23. Analog-To-Digital Converter Adjustments

1.Adjust A3A8R5 GAIN for a square wave displayed on the oscilloscope. The square wave should be approximately 4 V,,. See Figure 3-86 for location of adjustment.

Alternate Procedure 4. Procedure without using Low-Noise DC Supply:

a. Press QNSTR PRESET].

b. Key in TRACE A [BLANK] and SWEEP (SINGLE).

c. Disconnect cable 0 (black) from sweep ramp input A3A8Jl.

d. Short A3A8TP4 to A3A8TP5 or connect SMB snap-on short to A3A8Jl.

e. Connect DVM to A3A8TPll and ground to A3A8TP4. Set DVM for V ac.

f. Adjust A3A8R6 OFFS until the level at A3A8TPll is at a maximum ac voltage as indicated by the DVM (approximately

2.0 V ac). See Figure 3-86 for location of adjustment.

g.Remove short from A3A8TP4 and A3A8TP5. Reconnect cable 0 (black) to A3A8J 1.

h.Press ~NSTR PRESET].

i.Connect DVM to A3A8TP5 and ground to A3A8TP4. Set DVM for V dc.

j.Press SWEEP C-1. Note DVM reading at end of the sweep. The voltage will begin to drift immediately after the sweep ends. Therefore, the first indication after the sweep ends is the valid indication. It may be helpful to press [SINGLE) several times to ensure a valid indication at the end of the sweep.

k.If DVM indication is + 10.020 f0.005 V dc at the end of the sweep, no further adjustment is necessary. Otherwise, adjust A3A8R5 GAIN and repeat step j until the voltage at the end of the sweep is + 10.020 fO.005 V dc.

Adjustments 3-141