Instruction manual

AM16/32 Relay Analog Multiplexer

The average power required to operate an AM16/32 depends on the percentage

of time it is active per time period. For example, if a CR10X makes differential

measurements on 32 thermocouples every minute, the average current drain due

to the AM16/32 would be about ((.030 Sec/chan x 32 chan)/60 Sec) x 6 mA =

0.1 mA. Under the same conditions, a 2 second execution interval rate

increases the average system current drain to about ((.030 Sec/chan x 32

chan)/2 Sec) x 6 mA = 2.9 mA. At a minimum, the power supply must be able

to sustain the system between site visits anticipating the worst environmental

extremes.

If a 21X power supply is used to power the AM16/32, all low-level analog

measurements (thermocouples, pyranometers, thermopiles, etc.) must be made

differentially. Differential measurements are required because slight ground

potentials are created along the 21X analog terminal strip when the 12V supply

is used to power peripherals. This limitation reduces the number of available

analog input channels and may mandate the use of an external supply for the

AM16/32 (Figure 4).

FIGURE 4. Power and Ground Connections for External Power Supply.

Low supply voltage and high ambient temperatures affect the actuation time of

the multiplexer relays (Figure 2). If your program does not allow the relay

contacts sufficient time to close before a measurement is started, the result will

be inaccurate or overranged values.

4.2 Measurement Terminals

Most of the terminals on the AM16/32 are dedicated to the connection of

sensors to the multiplexer (Figure 1). Depending on the panel switch selection

(“4X16” or “2X32” mode), the sensor input terminals are organized into 16

groups (blue letters) of 4 sensor inputs or 32 groups (white letters) of 2 sensor

inputs. The terminals accept solid or tinned, stripped sensor leads. The four

“COM” terminals marked “ODD H, L” and “EVEN H, L” located by the mode

switch provide for attachment of the common signal leads that carry

multiplexed sensor signals to the datalogger.