How to read a sensor with a supplied table

Using Arduino Sensors
1

20220526_124007
20220526_1240071920×1081 192 KB

Hi all I wish to read the above sensor. I was looking at the Steinhart Equation but that wanted resistances at various temperatures.

Is there an a way to use this table?

My current circuit is 5v into the sensor and the out going to a0 with a 1k resistor to ground.

Thanks,
Chris

2

Maybe the MultiMap library would help.

1 Like
3

Please post a link to the sensor.

The table shows that the sensor response is nonlinear, in a rather ugly way. You would be much better off with a DS18B20, or even a thermistor.

Capture

1 Like
4

The sensor is a Haltech 1/8npt air temp sensor. I can't use another as for the application it is the only thing I have found that will fit. HT-010206 Air Temp Sensor - Haltech

5

Thanks I'll have a look at that library.

6

If you don't care about errors of +/- 10 degrees, the straight line fit works.

Other options include fitting a function to the curve, or interpolating between table data points.

7

Surprisingly, a cubic equation fits the data pretty well.

Capture

From the graph, the equation to calculate the temperature from the sensor voltage V is

float temp = 151.9 - 82.7*V + 23.7*V*V - 2.9*V*V*V;

2 Likes
8

Hello jremington
How do you generate the equation and diagram?

Have a nice day and enjoy coding in C++.
Дайте миру шанс!

9

I also confront similar question as you.....

10

Kaleidagraph. Very easy to use (much easier than Excel or any comparable spreadsheet) and does everything I want. https://www.synergy.com/

11

Merci and greetings to Down Under.

12

Thank you very much for this👍

13

Just to confirm I got this working to within a couple of degrees c at 0, 20 and at 80.

I believe this is a standard 'GM' sensor so this may be useful to others.

I have the sensor tied to a 10k resistor and ground on 1 side and 5v on the other.

This is my code.

float tempCalc(int tempReading){
  float tr = tempReading;
  volts = (1023 - tr) /1023 * 5;
 float tempC = (m0 + (m1 *volts) + (m2*volts*volts) + (m3*volts*volts*volts));
 return tempC;
}

with M0-3 being the values in jremingtons graph. I convert the temping reading to float because otherwise it ends up as 0 in the divide.

Any comments/improvements let me know.

14

Glad you got it working!

15

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.