HP Car 3490A manual Lqe, Orrra, Aojustmentprocedures, Ratioreferenceadjustments

Section V AOJUSTMENTPROCEDURES Model3490A

a.With 3490A set to l0 VDC RANGE, TRACK/ HOLD, SAMPLE RATE fully clockwise, and dc standard connected to input as in previous adjustment, set dc standardoutput to + 10.0000V.

b.Adjust A27R6, DA Gain, for display of

+10.0000 V. (Display will be noisy.)

S77. ResponseAdjustment.

5-78. This procedure requires a function generator(-hp- 3310A), a silicon drode, a l0kQ resistor and an oscilloscopehaving a delayed sweepand a delayed gate output (-hp l80C/DllOSlAllS2lA). The delayedgate output must be a negative-goingpulse with an amplitude of 2 to 200 V and a width of at least 30 nanoseconds.

a.Connect equipment as shown in Figure 5-7. If the 3490A has BCDiRemote Expand Option 020, also connect StretchedPulseOutput (J7 pin l0) to External Encode (J7 pin 28).

b.With 3490A set to l0 VDC RANGE and TRACK/ HOLD as in previousadjustment, set SAMPLE RATE to HOLD.

c.Set oscilloscope controls for External Trigger, negative slope and Main sweep. Set Main sweep to

.1 ms/div., Delayedsweepto I ps/div.

d.Set function generatorto squarewave, frequency to I kHz, and adjust output level for 20 V peak-to-peak signalas displayedon oscilloscope.

e.Adjust oscilloscopedelay control so that intensi- fied trace begins approximately 450 gs after negativg- going transition of square wave. Note 3490A readin$, which should be nearzero.

f. Adjust delay so that intensified trace begins approximately 120 ps after negative-goingedgeof square wave.

C. Adjust A27R3, Response,for display noted in stepe.

h.Remove top guard cover and move "5th Dgit Blank" wire from TestPoint M to Test Point L.

i.Replaceand securetop guard cover.

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Figure5-11. Locationof Ratio Adjustments.

a.Set 3490A FUNCTION to TEST, RANGE to 4. Set RATIO switch to EXT REF lV. Connect short betweenEXT REF Hig[ and Low terminals.

b.Connect dc standard to INPUT terminals and adjust standard output to + 10.0000 V. If the display indicates Overload, reverse the polarity of the dc standardoutput.

NOTE

Steps c and d adjust the zero setting of the Extemal ReferenceAmplifier and the Feed- back Amplifier. llith the 34904 set to Test

'4, the integrator charges to the Extemal 'Reference Amplifier output and dischmges to the ! 10.0000 V input. If the zero adjustments are set so that the amplifier output and the 3490A input voltageare the same polaity, the dßplay indicates Over-

load.

c.Adjust Al3Rl7 (Offset 3) for zero display.If the display goesto Overload,reversepolarity of dc standard output and slowly adjust Al3Rl7 in oppositedirection for zero display. Continue adjusting A13Rl7 with positive and negative 10.0000V inputs until display readszero I 0.0001V for either polarity input.

5.79.RATIOREFERENCEADJUSTMENTS.

5{0. Adjustment of the dc circuits, Paragraphs5-53 through 5{0. must be completedbefore beginningthe Ratio Reference Adjustments. A dc standard (-hp- 74OB),a I M t l0% resistor(hp- 0698-1051)and a stablevoltagesourcebetween9.5 V and 10.5V, suchas a mercun'battery (Mallory TRl77), are required for theseadjustments.Figure5-1I showsthe location of the Ratio adjustments.They are also shown on the top zuardcover.

d. Set RATIO switch to EXT REF I V. Adjust A13R8 (Offset 1) with positiveand negative10.0000V inputs for displayof zero t 0.0001 V.

e. Repeat steps c and d until display is zero

t0.0001 V for both positive and negativeinputs on both I V and 10 V EXT REF ranges.

f.Removeshort and connect I Mf2 resistorto EXT REF terminals.

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