Campbell AM32, Instruction Manual

AM32 MULTIPLEXER

3

FIGURE 3-1.  Hook-up diagrams for datalogger to AM32 connections.

3.1.1  RESET

Reset (RES) controls activation of the
multiplexer.  A voltage (3.5VDC < voltage <
16VDC) applied to this terminal activates the
multiplexer.  When this line is dropped to less
than 0.9VDC, the multiplexer enters a low
current drain state.  Reset is connected to a
datalogger control port.  Instruction 86  with
option code 41 - 48 (set port high) and 51 - 58
(set port low) is generally used to control the
port.

With older CR7s or 21Xs that do not have
Instruction 86 with port control capabilities,
Instruction 20 is used to control the port.

3.1.2  CLOCK

The clock line CLK controls the multiplexer
switching.  When the multiplexer is activated
with RES set high, the multiplexer's common
lines (COM HI, COM LO) are not connected to
any of the sensor input terminals.  When the

first clock pulse is received, the common lines
are connected to multiplexer channel 1 (1H,
1L).  When a second clock pulse is received,
the common lines are connected to multiplexer
channel 2 (2H, 2L); and so forth.  The
multiplexer is clocked on the leading edge of
the voltage pulse, (i.e. voltage level must raise
from 1.5VDC to above 3.5VDC to clock).  The
pulse width must be at least 5 ms.  An
additional delay is necessary before the
measurement to ensure that the relay has
adequate time to close.

With the CR10(X) a control port is generally
used to clock the multiplexer.  Instruction 86
with the pulse port option (command code 71
through 78 - pulse 10 ms) may be used to clock
the multiplexer.

With the CR7 and 21X, one switched excitation
channel is used to clock the multiplexer.
Instruction 22 should be programmed to provide
a 10ms delay with a 5000mV excitation.  If