321 Programmable Hardware Manual (PHM)
© Tibbo Technology Inc.
Details
Tibbit #22 is based on the MAX31865 15-bit RTD-to-digital converter IC. This Tibbit
can work with platinum RTD sensors (PT-RTDs) in the 100 Ohm to 1000 Ohm range.
Our Tibbo BASIC demo application (see below) supports PT100, PT200, PT500, and
PT1000 sensors (this is selectable in code, see the main.tbs file).
In addition to the MAX31865 IC, this Tibbit also carries a PIC16F1824
microcontroller. The microcontroller interfaces the converter IC to the main CPU of
the TPP board. With the right firmware, it can also be used for data preprocessing
(for example, for averaging of measurements with the purpose of increasing
measurement precision).
Combine this Tibbit with #21 (four terminal blocks), #20 (nine terminal blocks) or
#19 (DB9M connector). It's not common but possible to use the latter for wiring into
the meter's inputs.
Tibbit #22 is very accurate. Here are the results of measurement comparisons
between the Tibbit #22 and a Fluke 726 process calibrator:
·
PT100 sensor: Measurements performed by the Tibbit deviated from those of the
calibrator by no more than 0.5 degrees C in the temperature range from -100C to
+400C. The error did not exceeded 2.5 degrees C outside of this temperature
range.
·
PT1000 sensor: Measurements performed by the Tibbit deviated from those of
the calibrator by no more than 0.5 degrees C in the temperature range from -125C
to +550C. The error did not exceeded 2.5 degrees C outside of this temperature
range.
Connecting the RTD sensor
You can use 2-wire or 4-wire sensor connection. The 2-wire connection does not
allow the system to compensate for errors caused by cable resistance. Therefore,
this type of connection is suitable for cases where the sensor cable is short:
The 4-wire connection eliminates errors caused by cable resistance. It is
recommended for cases where the sensor is located at some distance from the
Tibbit.
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