Measuring PT1000 using op-amp

Other Hardware Sensors
1

Hi there, i have a project in which i have to measure temperature sensor (PT1000RTD) using op amp where, the supply voltage is 24VDC, output must be in between (0-10) 0-50 degree.
if 0v it should read 0 and it should read 10 when the temperature rises up to 50 degree. The output of op-amp will be connected to microcontroller.

I used the below circuit

ppu
ppu740×462 31.5 KB

I simulated the circuit but i could not read exact (0-10)(0-50 degree) readings.

I am thinking of using it in single supply mode and therefore, i will need to use voltage regulator that converts 24VDC to fixed 5VDC.

image

2

You have the Proteus simulator. Try increasing R4 and see what happens

3

it is displaying same value.
I changed the resistor R4 val to 20k

4

You are missing the connection between U1A pin 2 and the junction of R1 and R2

5

aws
aws1040×515 84.2 KB

as per my knowledge they are connected, could you please point?

6

x
x1035×511 96.1 KB

1 Like
7

Hi,
Can you please post a link to data/spec of your PT1000?
Is it a 2, 3 or 4 wire version?

What model Arduino controller will you be using?

Why use an Op-Amp when there is a purpose built module for the PT1000 and Arduino?

Have you Googled;

pt1000 arduino tutorial

Have you looked at a table for the PT1000 resistance vs temperature?

Tom.. :smiley: :+1: :coffee: :australia:

8

Where did those voltage numbers come from? If R1 = 10k, R2 = 1k and V across the divider is 5V, the V across R2 will be 1/11 * 5 = 0.4545V, not 0.1479.

9

Its a two wire because i dont want to get into any complexity at the moment, i wanna build a simple op amp temperature sensor thats it

10

I took it from internet and simulated it just to see the output.

Ill change the resistor value and try

12

When you get to actually building it you will want to get a better op-amp than trying to over come the short comings of the LM358. There is a reason there are instrumentation amps.

13

And then there are the shortcomings of measuring a thermistor with the 10-bit Arduino A/D,
poor resolution at the temp extremes, and the calibration problems.

Why use an opamp when there is a specialised chip for the PT1000.
See post#7.

Might as well use a DS18B20 if you are going to measure a PT1000 with an opamp.
No calibration, and a better resolution.
Leo..

14

Yes, i have used it now in my schematic and i believe that things would work fine

15

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