AM25T Solid-State Thermocouple Multiplexer
3
4.3 Power (12V)
The AM25T requires a 9.6 to 16 Vdc (12 Vdc nominal) power supply.
In low current drain applications, it is convenient to power the AM25T from
the data logger battery. For power intensive operations, use a high amp hour
12 Vdc battery.
See Campbell Scientific’s application note on power supplies
https://s.campbellsci.com/documents/us/technical-papers/pow-sup.pdf
) for
information on calculating the power requirements for a system.
4.4 Power Ground (G), Ground Terminals (
⏚
)
Each differential input channel has a ground terminal located next to it. The
ground terminals (
⏚
) are common with the power ground (G) and the ground
lug on the base. Connect the sensor shields to the ground terminals (
⏚
). Always
tie the data logger and multiplexer to a common earth ground via the ground
lug.
4.5 Analog Ground (
⏚
)
The analog ground terminal is the ground reference for the AM25T reference
temperature measurement. It is the
⏚
terminal located between the
VX
and
HI
terminals. Analog ground is not common with the other ground terminals
labeled
G
.
The analog ground terminal must be connected to the data
logger ground as shown in TABLE
4.6 Reset (RES)
A control terminal is used to operate the
RES
channel. The AM25T is reset
and activated by applying and holding 5 Vdc to the
RES
channel. Once the
AM25T is activated, the AM25T reference temperature can be immediately
measured. The AM25T enters its quiescent state when the
RES
channel is set
to
0
Vdc.
4.7 Clock (CLK)
Pulsing the
CLK
channel sequentially advances the relays. A control terminal
is used to operate the
CLK
channel.
The first
CLK
pulse advances the relays to the reference temperature excitation
channel. The second
CLK
pulse advances the relays and connects
HI
and
LO
to
1H
and
1L
on the multiplexer.
Two clock pulses are required to advance to the next adjacent
sensor input channel on the AM25T.
The fourth
CLK
pulse advances the relays and connects
HI
and
LO
to
2H
and
2L
. The sixth
CLK
pulse advance the relays and connects
HI
and
LO
to
3H
and
3L
. This sequence is continued for the remaining input channels.
NOTE
