Model34904

ADJUSTMENTPROCEDURES

Section V

s.Set RATIO switch to EXT REF I V' Adjust efgni (Bias. Atlj.) with both positive and negative 10.0000V inputsfor displayof zerot 0'0005V'

h. Repeatstepsa through g until all readingsare

colTect.

i.DisconnectlMft resistorfrom EXT REF termi nals. Set RATIO switch to INT REF, FUNCTIONto DC,RANGEttr 10V.

i.Connect a mercury battery between9'5V and 10.5V. or other floating voltagesourcestablewithin

-to Higfr,+ to Low'Note1mV/hr, to INPUTterminals,3490Areading.

k.Connectdc standardto EXT REF terminalsand setstandardoutput to positivevoltageequalto negative readingin stePj.

l.SetRATIOswitchto EXT REF l0 V- Note3490A display.

m.Reversethe polarity of the voltageat both the INPUT and the EXT REF terminalsAdjust.Al3Rl7, repeatingstepsk throughm until thereadinginstepI is equalto the readingin stepm. (Polarityshouldbe- for both readings.)

n.ReduceEXT REF voltageto l/10 the voltage

selectedin stepk. S€t RATIO switchto EXT REF I V. Withmercurybatteryconnectedto INPUT,- to HIGH,+ to LOW,note3940Adisplay.

o.Reversethe polarity of the voltageat both the INPUT and the EXT REF terminals.Adjust Al3R8, repeatingstepsn and o until the readingin stepo is

equalto the readingin stepn. @olarityshouldbe - for both readings.)p.Repeatstepsj through o until all readingsare correct.q.Connectmercurybatteryto IMUT terminals,- to HIGH,+ to LOW.

r.Connectdc standardto EXT REF terminalsand setstandardoutput to positivevoltageequalto negative readingin stepj.

s.Set RATIO switch to EXT REF lOV. Adjust Al3Rl4 (10V Adj) for displayof - 10.0000.

t.ReduceEXT REF voltage to l/10 the voltage selectedin stepk (positive).SetRATIO switchto EXT REF I V. Adjust Al3Rl2 (lV Adj) for displayof

-10.0000.

u.Set RATIO switch to INT REF, FUNCTIONto TEST, RANGE to 3. This test alternatespositiveand negativereadingsIfthe. readingsarenot equalt I count and between ! 0.99992 and ! 0.99999, adjust

AlAlR3lT C Refl to obtain this condition. Record bothreadings(afteradjustment).v.Set RATIO switch to EXT REF l0V. Apply

-10.0000V to EXT REF terminals. Readingswill alternate+ and - as in previousstep. Recordpositive reading.

w.AdjustA13Rl9 (Offset301) for positivedisplay" equalto(positivereading,stepu) + (positivereading,stepv)

L

x.Adjust AlAlR3lT for positive display equal to positivereadingin step u.

y.Positiveand negativedisplaysshould now be equal t I count, and equal to readingsrecorded in step n + I count, respectively. If not, repeat this adjustment procedure(stepsa through x).

z.Perform DC Amplifier Adjustment, Paragraph

s-59.NOTE

In order to operate the 3490A with the Ratio AssemblyA I 3 removedandtheRatio JumperAssemblyA26 insertedin itsplace, it will benecessaryto perform theReference Adiustmens,Paragraph5-57.

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