Tool/software:
Dear Specialists,
My customer is evaluating XTR105 and has a question.
I would be grateful if you could advise.
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Using the circuit diagram in Figure 6-3 on page 13 of the XTR105 datasheet,
I confirmed the operation of a PT100 3-wire RTD circuit.
After adjusting the offset and gain with a cable less than 50 cm long,
I extended the cable to 2.5 m and measured the temperature. The temperature was approximately 22°C compared to an ambient temperature of 27°C.
When a 24V power supply was applied:
When the cable length was 50 cm: Current: 13.9 mA, converted to a temperature of 27°C.
When the cable length was 2.5 m: Current at 24V applied: 12.53 mA, converted to a temperature of 22°C.
The PT100 is connected via a cable from the terminal block.
Even with a 2.5m cable length (specified for -10°C to 50°C),
When B and b of the PT100 were shorted at the terminal block, the temperature measurement was within 27±1°C.
Question(1) For a 3-wire RT: What is the maximum cable length that can be used?
Question(2) Is it necessary to adjust the offset each time the cable length is changed?
Question(3) Could you please let me know the reason and solutions?
---Condition
Operating temperature: Set each value from -10°C to 50°C.
The values of RZ, RG, RLIN1, and RLIN2 were calculated according to the formula in Table 7-1 on the datasheet.
RZ=96.0886: Adjusted using the volume resistor. Corresponding fixed resistance: 43 Ω and volume resistor: 20 Ω.
RG=47.0376: Adjusted using the volume resistor. Corresponding fixed resistance: 91 Ω and volume resistor: 10 Ω.
R1 = 107.79
R2=119.39
Rlin1 = 55.52 kΩ
Rlin2 = 58.133 kΩ
The wiring resistance values for 2.5 m are as follows:
1: 0.1838 ohms
2: 0.2126 ohms
3: 0.1941 ohms
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I appreciate your great help in advance.
Best regards
Shinichi
