Apogee Instruments ST-200 Panduan Pemilik - Halaman 11

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ST-150

The ST-150 does not include bridge resistors and therefore requires measurement with dataloggers or controllers

that are capable of current excitation. Although the ST-150 can be used in a 2-wire or 3-wire measurement

configuration, a 4-wire configuration is recommended for highest accuracy (4-wire measurement configuration

eliminates the influence of lead wires). In the 4-wire configuration, an excitation current is applied across the PRT

with two of the lead wires, voltage is measured across the other two lead wires using a differential measurement,

and resistance of the PRT is calculated by dividing the measured voltage by the excitation current (Ohm's Law).

Current does not flow in the wires where voltage is measured, so resistance of the lead wires does not influence

the measurement. Temperature of the PRT is calculated from resistance using equations (2) and (3) on page 13. If

a half-bridge measurement is desired, the same wiring and bridge resistors detailed below in the ST-300 section

can be used to make the measurement.

White: Current excitation

Black: Ground

Yellow: High Side of Differential Channel

Blue: Low Side of Differential Channel

Clear: Ground (shield wire)

Note: as shown in the

schematic, the 4-wire PRT can

be directly measured. The black

and blue wires are electrically

connected to one side of the

PRT while the yellow and white

wires are electrically connected

to the other side of the PRT.