Instruction manual

AM16/32 Relay Analog Multiplexer

result in an approximate one degree measurement error. Installing the

aluminum cover plate (included with AM16/32) helps to minimize

gradients. For best results the AM16/32 should be shielded and

insulated from all radiant and conducted thermal sources. When an

enclosure is used, gradients resulting from heat conducted along the

thermocouple wire can be minimized by coiling some wire inside the

enclosure. This technique allows heat to largely dissipate before it

reaches the terminals. If the AM16/32 is housed in a field enclosure,

the enclosure should be shielded from solar radiation.

FIGURE 19. AM16/32 Aluminum Cover Plate

6.6.2 Single-ended Thermocouple Measurement

In single-ended thermocouple measurements, the following

precautions must be taken to ensure accurate measurement:

Only shielded thermocouple wire should be used; the sensor shields

should be tied to multiplexer input shield (“

”) terminals.

Exposed ends of thermocouples measuring soil temperature should be

electrically insulated to prevent differences in ground potential among

the thermocouples from causing errors in the measured temperatures.

AM16/32 panel switch set to “4X16” mode.

Sensor to Multiplexer wiring - up to three thermocouples per SET; the

high side of each thermocouple is input into terminals ODD H,

ODD L, and EVEN H. The low sides of each thermocouple are

multiplexed in common through terminal EVEN L.

Multiplexer to Datalogger wiring - If the reference junction is at the

datalogger, then the wire that connects the COM ODD H, COM ODD

L, and COM EVEN H terminals to the datalogger should be of the