Campbell AM25T Spezifikationen PDF herunterladen (Seite 10)

AM25T Solid State Multiplexer

AM25T

FIGURE 2. External Battery Connections

4. Sensor to AM25T Wiring

This section and the examples describe differential voltage measurements of

thermocouples. It is possible to make single-ended measurements with the

AM25T, however they are more likely to have problems (Appendix A).

Shield wires are connected to the ground terminal next to the measurement

channel and left unattached at the sensor.

4.1 Thermocouple Measurement

An internal reference RTD is located in the AM25T. This reference

temperature does not require an additional datalogger input to measure the

reference. The RTD is located in the center of the multiplexer on the strain

relief flange.

Thermal gradients between the AM25T's sensor input terminals and the RTD

cause errors in thermocouple readings. For example, a one degree gradient

between input terminals and the RTD will result in a one degree measurement

error. The central aluminum (strain relief) bar and the cover are designed to

reduce gradients.

Heat conduction along the thermocouple wire, into the terminal strips, can be

reduced by coiling some excess lead wire inside the enclosure.

The datalogger manual contains a thorough discussion on thermocouple

measurements and error analysis. Consult the datalogger manual for more

details.

For a differential voltage measurement of a thermocouple, wire the high side of

the thermocouple to the high side of a differential input channel and the low

side of the thermocouple to the low side of the channel. Thermocouples that

follow the U.S. industry standards use red insulation on the low side of the

thermocouple. Wire one thermocouple per differential input channel

(Figure 3).

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 35 36

Keine Kommentare

Campbell AM25T Spezifikationen Seite 10