Specifications

6
Multiplexer Selection Guide
Choose between the broad functional-
ity of the 34901A, the high speed
scanning of the 34902A, or the single-
ended density of the 34908A. These
three modules are the only way to
connect to the 34970A internal DMM.
They can be used to scan with exter-
nal instruments as well.
All multiplexer modules employ
break-before-make scanning, ensuring
only one closed channel (or channel
pair) at a time. Multiple channel clo-
sures are allowed on the 34901A and
34902A modules when not configured
for scanning.
The 34908A does not allow multiple
channel closures at any time.
Agilent 34901A
20-Channel
General-Purpose Multiplexer
• 60 ch/s scanning
• Two- and four-wire scanning
• Built-in thermocouple reference
junction
• 300 V switching
The 34901A is the most versatile mul-
tiplexer for general purpose scanning.
It combines dense,
multi-function switching with
60 channel/second scan rates to
address a broad spectrum of data
acquisition applications.
Two- and four-wire channels can
be mixed on the same module.
Two additional fused inputs (22 chan-
nels total) route up to 1A of current
to the internal DMM, allowing ac and
dc current measurements without the
need for external shunt resistors.
Backplane Switches
Internal
DMM Input
01
10
Com
H
L
H
L
H
L
H
L
H
L
H
L
I
L
I
L
I
L
I
L
H
L
H
L
T
Com
(4W Sense)
11
20
21
Current
Channels
22
Com
(Current)
Fuse
Fuse
Internal
DMM Input
(4W Sense)
Internal
DMM Input
(Current)
Reference
Junction
Sensor
Channel Switches
Bank Switch
Shunt Switches
34901A 34902A 34908A
Number of Channels 20 + 2 16 40
Max scan speed 60 ch/s 250 ch/s 60 ch/s
Number of contacts 2 or 4 2 or 4 1
Temperature
Thermocouple •••
2-wire RTD •••
4-wire RTD ••
Thermistor •••
dc Volts •••
ac Volts •••
2-wire Ohms •••
4-wire Ohms ••
Frequency •••
Period •••
dc current •
ac current •