Campbell AM32, Instruction Manual

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AM32 MULTIPLEXER
2
With limitations, it is possible to multiplex
selected sensors of different types (e.g.
thermocouples and soil moisture blocks, see
example in section 7.3). In some cases, the
AM32 is used to multiplex sensor excitation or
continuous analog outputs.
An enclosure is required for field use. For
thermocouples the AM-ENCT enclosure is
recommended to reduce thermal gradients
across the AM32. If thermocouples are not
being measured, use the model AM-ENC
enclosure.
2.0 SPECIFICATIONS
Power* unregulated 12 VDC (9.6 V
to 16 V) - See Figure 4 for
implications of low power to
relay actuation.
Current drain
Quiescent < 15uA
Active 25mA (average)
Reset
*
> 3.5 V active;
<1.5 V inactive
Clock* Clocks on the rising edge
from < 1.5V to > 3.5V,
5msec minimum pulse
width.
Operating Temp. -40oC to +65oC
Operating humidity 0 - 95%, non-condensing
Dimensions (L x W x D)
Without field encl. 21.6 x 16.5 x 2.5 cm
(8.5" x 6.5" x 1.0")
Field enclosure 34.3 x 28.7 x 14.1 cm
(13.5" x 11.3" x 5.5")
Weight 2 lbs (approx.)
in enclosure 12 lbs (approx.)
Max switching cur.** 500mA
*
Reset, Clock and +12V inputs are limited to
+16V by 1.5KE20A transzorbs.
** Switching currents greater than 30mA
(occasional 50mA is acceptable) will
degrade the contact surfaces of the
mechanical relays, increasing their
resistance. This process adversely affects
the suitability of these relays to multiplex
low voltage signals. Although a relay used
in this manner will not be of use in future
low voltage measurements, it may continue
to be used for switching current in excess of
30mA.
CONTACT SPECIFICATIONS
Initial contact resistance .050 ohm max.
Initial contact bounce 1ms max.
Contact material Gold clad silver alloy
Electrostatic capacitance 3pF
Minimum expected life
Mechanical (at 50cps) 108 open
Electrical (at 20cps) 105 open at 4A
250V DC
2x105 open at 3A
30V DC
CHARACTERISTICS at 25
o
C, 50% RH
Operate time 8 to 15 ms (See Figure 4.)
Release time 5 ms approx.
3.0 OPERATION
3.1 THE CONTROL TERMINALS
The control terminals are located along the left
terminal strip as shown in Figure 1-1.
The CR10(X), 21X and CR7 dataloggers are
connected to the AM32 as shown in Figure 3-1.
The maximum terminal opening is 1.5 mm,
about the size of a 12 gage wire.
The CR10(X) 12VDC supply and ground
terminals are connected to the AM32 12V and
ground terminals. One control port is used for
clocking and one for reset.
With the CR7 and 21X, the 12V and ground
terminals are connected to the AM32's 12V and
GND terminals. One control port is used for
reset, and one
switched excitation channel is
used for clock.