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d .
Switch the frequency of the calibrator signal between 300Hz and
10kHz , and adjust R113 , until the reading is the same for both
frequencies (within a tolerance of ± 3 counts) .
Adjustment: R121 (AC stage DC offset voltage)
ADJUST AT 10KHZ
R121 gives the ability to reduce the DC offset voltage produced by the
source follower circuitry of Q100 and Q101 . When there is too much
offset , switching between ranges , especially the 2V and the 20V ranges ,
will create temporary charge in the True RMS circuitry , that will disturb
proper autoranging.
Re - adjustment is needed when the reading 'jumps '
more than 200
counts
when
switching between
the
2VAC and the
20VAC range . If necessary , perform the following procedure:
f.
g .
h .
i .
j.
k.
1 .
Adjustment: AC Voltage ranges.
m.
n.
Disconnect the AC Voltage calibrator and connect the shorting
plug to the LOW and V/ 2 / TEMP jacks.
Select the 20 Volt AC range .
Measure the voltage at U101 pin 7 (the AC amplifier output ) with
a Digital Multimeter using a mV range .
DM2510/ DM2510G
Page 12 of 17
Adjust R121 to reduce the DC voltage at that point to less then
20mV .
Turn the power off, replace the top of the cabinet on the power
and allow the instrument time to warm up .
Set the DMM in the AC , 200mV
range .
Connect the AC Voltage calibrator to the LOW and V/
/TEMP
jacks.
Set the calibrator to 10.000mV AC @ 300Hz .
Press the DOWN and UP of Autoranging
keys simultaneously .
The DMM will then store this measurement in RAM memory and
show " 190. ?' on the display.
Adjustment Procedure
May 6 , 1994
Revision A
1
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