Instruction manual

AM16/32 Relay Analog Multiplexer

1. Function

The primary function of the AM16/32 Multiplexer is to increase the number of

sensors that can be measured by a CR1000, CR23X, CR10(X), 21X, or CR7

datalogger. The AM16/32 is positioned between the sensors and the

datalogger. The AM16/32 is a replacement for CSI’s AM416 and AM32

models. Mechanical relays in the AM16/32 connect each of the sensor

channels in turn to a common output destined for the datalogger. The user

program advances the multiplexer through the sensor channels making

measurements and storing data.

A slide switch located on the AM16/32’s top panel selects one of two modes of

operation. In “2X32” mode the multiplexer can scan 32 sensor input channels,

each with two lines. In “4X16” mode it can scan 16 input channels with four

lines a piece. The datalogger program is written according to the selected mode

and the sensors to be measured.

The maximum number of sensors that can be multiplexed by an AM16/32

depends primarily on the type(s) of sensors to be scanned. The following

guidelines assume identical sensors:

Up to 32 single-ended or differential analog sensors that do not require

excitation. For example: pyranometers and thermocouples (see Sections 6.1,

6.2, and 6.6).

Up to 32 single-ended sensors that require excitation. Example: some half

bridges (see Section 6.3.1).

Up to 16 single-ended or differential sensors that require excitation. Examples:

full bridges and four-wire half bridge with measured excitation (see Section

6.3.3 and 6.4).

In conjunction with a second AM16/32, up to 16 six-wire full bridges (Section

6.5).

1.1 Typical Applications

The AM16/32 is intended for use in applications where the number of required

sensors exceeds the number of datalogger input channels. Most commonly, the

AM16/32 is used to multiplex analog sensor signals, although it can also be

used to multiplex switched excitations, continuous analog outputs, or even

certain pulse counting measurements (i.e., those that require only intermittent

sampling). It is also possible to multiplex sensors of different, but compatible,

types (e.g., thermocouples and soil moisture blocks, see Section 6.7.1).