0
\$\begingroup\$

circuit

For the circuit shown in Fig. 3, the bridge is balanced when T=100 C. That is R1=R2=R3=R4=10k ohm. The thermistors are matched, and their resistance related to temperature by RT=4130.65+0.15T^2 where T is the temperature in Kelvin. Determine Vo for the following temp: (i) T=120 C (ii) T=80 C

I'm confused, because when evaluating the RT, using T=100C, it's equal to 25016.79 ohm, am I missing something?

\$\endgroup\$
2
  • \$\begingroup\$ user16780029 - Hi, Where did that schematic image originally come from? In order to comply with the site rule on referencing of copied or adapted material, details of the original source of copied or adapted material must be provided. If the source is online (webpage, PDF, video etc.) then edit the question & add its name & link (URL). If the source was a printed book or other offline material, then edit the question & add a normal citation (see the linked rule for details). TY \$\endgroup\$ Commented Mar 9, 2024 at 10:21
  • \$\begingroup\$ Actually the question is from a study material, I'm not sure what reference the lecturer got it from. \$\endgroup\$ Commented Mar 10, 2024 at 10:22

2 Answers 2

Reset to default
0
\$\begingroup\$

I don't think you're missing anything, this just looks like a mistake, assuming you faithfully copied the text. You need to attribute the image (eg. publication and page number), it's a rule.

The equation for Rt is a bit weird for a thermistor- it more resembles that of an RTD, though there's a linear term missing.

\$\endgroup\$
1
  • 3
    \$\begingroup\$ Attribution would be very nice to steer people away from a book with awful illustrations. Yuck. I wonder if the text and formulas within are similarly lousy. \$\endgroup\$ Commented Mar 8, 2024 at 17:41
0
\$\begingroup\$

The thermoresistance value at 100°C is correct. The thermistor is a non-linear device, as can also be seen from what TI shows in the relevant manual:

enter image description here About thermistors from TI see: https://www.ti.com/lit/an/snoaa12/snoaa12.pdf?ts=1709904262202&ref_url=https%253A%252F%252Fwww.google.ch%252F

My calculation of output voltage:

enter image description here

By placing the circuit in a feedback loop it is possible to obtain a linear response vs. x.

\$\endgroup\$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.