HP 3457A Service Manual page 207

+10V REF
4
TO sM101
34520 F.12.24 |
Figure 8-7. Current Source, Gain Select and Divider Circuitry
Test 6 checks the operation of the amps function voltage sensing on assembly A2/1, It does this by ap-
plying ImA from the ohms current source to A2R401 (corresponds to 1.5 amp range) and making a
normal current measurement. The Main Controller (A1U501) configures the measurement section for
the 3.0 amp DC current function, 10 power line cycle integration time with the fixed input impedance
mode off. A/D Controller, A2U501 then configures the ohms current source for [mA and switches on
K201, K301 and K302. This routes the ImA current through U402 $3 and K402 (pins 13 - 11) to the 0.1
ohm shunt (R401). The voltage across R401 is sensed at input hybrid UIOI pin 40 by closing U403 SI
and $2. A normal DC current measurement is made and the result is sent to the Main Controller for
error checking to ImA +500uA. Figure 8-8 illustrates some of the circuitry used for this test. If a
failure is detected and the AUXNERR? command is executed, the number 64 will be displayed on the
control panel if their are no other errors (See Table 8-2).
HP 3457A Multimeter
8-42