Agilent 34970A/34972A Data Acquisition / Switch Unit

Chapter 5 Theory of Operation
Internal DMM
Input
Unless otherwise noted, components in this discussion are located on the
A4 circuit assembly (34970-66504).
The purpose of the Input section is to connect the Input HI terminal to the
various measuring functions. This is accomplished through K102, K103,
and K104. Additionally, connections are made for the 4-wire ohms
HI Sense and LO Sense inputs. Shunt selection (ranging) and voltage
sensing are also performed for the current function. The table below
shows the state of each relay for each measuring function. All relay coils
are driven from U150.
Functional K102 K103 K104 Sense at:
0.1 V - 10 VDC
100 V - 300 VDC
2-Wire Ohms
4-Wire Ohms
AC Voltage
Frequency/Period
3 A, 1A DCI
100 mA, 10 mA DCI
1A AC I
Set
Set
Reset
Reset
Set
Set
Reset
Set
Reset
Set
Reset
Set
Set
Reset
Reset
Reset
Reset
Reset
Set [1]
Set
Reset [2]
Reset [2]
Reset
Reset
Reset
Reset
Set
U101-5
U102-12
U101-5 [3]
AC_IN
AC_IN
U101-10
U101-10
AC_IN
[1] K104 will be reset when input resistance is selected to >10,000 M through the menu.
[2] K104 will be set for the 100 M range.
[3] Configurations shown are for the current source output (HI) terminal. The measurement
sense is accomplished through the Sense HI / Sense LO terminals.
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