I have a 2K iso-curve thermistor with the following:
5700ohms @ 0 degrees C
2001ohms @ 25 degrees C
time constant (63% response) of 12 seconds
Low Range: -2.46C to 21.4C
High Range: 10.08C to 36C
Wide Range: -0.34C to 32.17C
The idea is to connect to a mosfet to choose the different ranges for the wheatstone bridge and then connect to the arduino. Coding is going to be my next issues, but for now does this sound like a good idea. The thermistor I have is from the 1970's and I am hoping to make it work.
but for now does this sound like a good idea.
A good idea for what? What do you want to achieve? To read the temperature with an Arduino there are much simpler methods.
I had meant, was connecting it to a mosfet, with the wheatstone bridge a good idea.
What I am hoping to do is set this temperature sensor up to the arduino, and datalog the resulting temperatures. The last calibration sheet I have gives me this equation: TempC= A + B N + CN^2
The coefficients for the last calibration are as follows: A: -2.2723; B: 3.2214 -E02; C: 5.3569 -E06
I am getting some readings with the following code (I have not connected this to a brdige/mosfet), it is not the most accurate of readings at the moment, and am hoping someone may have a solution. This code is slightly changed from one I found online, and does not include datalogging code.
#include <math.h>
// Analog pin number, and input voltage for temperature sensor
int tempPin = 0;
float aref_voltage = 4.96;
double Thermister(double RawADC) {
double Temp;
Temp=((-2.2723)+(.032214RawADC)+(.0000053569RawADC*RawADC));
return Temp;
}
// ------thermistor
void setup() {
// Open serial for output
Serial.begin(9600);
}
void loop() {
// read the value from the temp sensor:
double sensorValue = analogRead(tempPin);
Serial.print("sensor value: ");
Serial.println(sensorValue);
// Calculate mV from temp sensor output
double voltage = sensorValue * aref_voltage;
voltage /= 1024.0;
Serial.print("voltage: ");
Serial.println(voltage);
Serial.print("temperature: ");
Serial.println(double(Thermister(analogRead(0))));
Serial.println("\n");
// Wait a sec before turning off status LED
delay(3000);
}
// Calculate mV from temp sensor output
double voltage = sensorValue * aref_voltage;
voltage /= 1024.0;
This does not calculate mV but V, but it seems that's what the rest of the code expects anyway.
I had meant, was connecting it to a mosfet, with the wheatstone bridge a good idea.
You might have to describe that in detail, I don't understand what you're trying to do. You already have the resistance values for the two basic temperatures, what do you need the wheatstone bridge for then? What kind of role does the MOSFET play in this equation?
The mosfet was going to be to choose between different values of resistors for the different temperature ranges.
In the old setup that this thermistor was connected to, it gave the option to choose between Low range, High Range, and Wide Range. Although this may not be necessary to do anymore. Most likely it should be sufficient to leave this setup for the low range, and it is going to be recording sea water temperatures, which it is doubtful that it will go above 20 degrees celsius.
I may even be reading this sensor completely wrong as the paperwork for the old setup states "Sensor is based on a thermistor controlled oscillator with frequency 2048-4096 Hz"
Can you post the schematics of the intended wiring? My guess is, that the circuit you currently have in mind will probably not work but there's a lot of guessing on my side.