PN结的温度/电压的线性度非常好，但是个体之间的一致性不好，即互换性不好

here is the code.

============16f684 diode temp measurement================

#include <htc.h>
#include <string.h>
#include "delay.h"
//#include "lcd_4bit.h"
#include "lcd_3wi.h"

__CONFIG(MCLRDIS & BORDIS & WDTDIS & PWRTEN & INTIO);

#define sleep()                        asm("sleep")                //put the mcu to sleep
#define AN0                                (1<<0)                                //an0
#define AN2                                (1<<2)                                //an2 - an1 used a vref in this application
#define ADC_CH0                        AN0                                        //adc on an0
#define ADC_CH1                        AN2                                        //adc on an2
#define LCD_Line_ADCX        LCD_Line0                        //L ch on lcd_line0
#define LCD_Line_Temp        LCD_Line1                        //R ch on lcd_line1
#define LED_PIN                        (1<<5)                                //led on GPIO1
#define PA_SET(bits)        PORTA |= (bits);        //set bits on porta
#define PA_CLR(bits)        PORTA &=~(bits);        //clear bits on porta
#define PA_FLP(bits)        PORTA ^= (bits);        //flip bits on porta
#define DLY_main_loop        300                                        //main loop delay, in ms
#define Vref                        2000000ul                        //reference voltage, in uv. Vref=2v
#define adc2_uv(adc_int)        ((signed long) (Vref*((unsigned long)adc_int))>>10)                //convert 10 bits to uv. so 1000 = 1mv.
//caliberation temperatures
#define T1                                0l                                        //1st caliberation temperature, in 0.01C
#define adc_uv_at_T1        699218l                                //adc reading, in uv, at T1
#define T2                                10000l                                //2nd caliberation temperature, in 0.01C
#define adc_uv_at_T2        750000l                                //adc reading, in uv, at T2
#define uv2_tempC(uv)        T1+(signed long) (T2-T1)*((uv)-adc_uv_at_T1)/(adc_uv_at_T2-adc_uv_at_T1)        //convert uv to C. 2 decimal points
#define Tacq_delay()        NOP(); NOP(); NOP(); NOP(); NOP(); NOP()        //delay for tacq

const unsigned char str_adcx[] ="ADC :           ";
const unsigned char str_volt[] ="Volt:         uv";
const unsigned char str_tempC[]="Temp:          C";
const unsigned char str_0[]="16F684 TempMeter";
const unsigned char str_v[]="version 0.2-1234";
unsigned char vRAM[17];

unsigned long random_vN(void) {        //using von Neumann middle square approach to return a random number
        static unsigned long seed=5634;        //3021, 3421
        seed=((seed*seed) & 0x00ffff00) >> 8;
        return seed;
}

void adc_init(void) {                                        //initialize the adc
//        ADCON0 = config_mask;
        ADCS2=0, ADCS1=1, ADCS0=0;                        //adc running at fosc/32
        ADFM=1;                                                                //adc results right justified
        VCFG=1;                                                                //Vref on porta2/an2
        ADON=0;                                                                //adc off
}

unsigned int adc_read(unsigned char ch){//read adc
        ADON=1;                                                                //turn on the adc
//        ANSEL |= ch;                                                        //select the adc channel, and adc at fosc/32
//        TRISIO |= ch;                                                //turn it as input
//        CHS1=(ch-1) >> 1;                                                //select the channel
//        CHS0=(ch-1);
        switch (ch) {
                case AN0: CHS2=0, CHS1=0, CHS0=0, ANSEL=AN0; break;
                case AN2: CHS2=0, CHS1=1, CHS0=0, ANSEL=AN2; break;
                default: NOP(); NOP(); NOP(); NOP(); NOP(); break;
        }
//        delay_us(1);                                                                //turn on the adc
//        may need some delays here
        Tacq_delay();                                                //delay for tacq
        GODONE=1;                                                        //start the adc
        while (GODONE) continue;                        //wait for the adc to complete;
        ADON=0;                                                                //turn off the adc
        return (ADRESH<<8) + ADRESL;
//        return random_vN() & 0x3ff;                        //return a random 10bit number, for testing purposes
}

void ltoa(char *s, signed long ul, unsigned char length) {        //convert unsigned long to a string, 3 dps
        unsigned char i;
       
        if (ul<0) {
                ul=-ul;
                *s++='-';
        } else *s++='+';
       
        i=length;
        do {
//                if (i==(length-3)) s[i--]='.';
                s[i--]=ul % 10 + '0';
                ul = ul / 10;
        } while (ul);
}

void mcu_init(void) {
        CMCON0=0x07;                                //turn off comparators;
        //TRISIO=0b11;                        //input on GPIO0, all others digital output;
        ANSEL=0x00;                                //all ports gpio
        IRCF2=1, IRCF1=1, IRCF0=0;        //4Mhz
}

void main(void)
{
        //unsigned char temp=0, gSPad[9], i;
        unsigned int i, tmp, tmp2;
        //unsigned int val_L, val_R;
       
        mcu_init();                                //initialize the mcu
        lcd_init();                                //initialize the lcd
        adc_init();                                //initialize the adc
        strcpy(vRAM, str_0); lcd_display(LCD_Line0, vRAM);
        strcpy(vRAM, str_v); lcd_display(LCD_Line1, vRAM); delay_ms(50);
        strcpy(vRAM, str_adcx); lcd_display(LCD_Line_ADCX, vRAM);
        strcpy(vRAM, str_tempC); lcd_display(LCD_Line_Temp, vRAM);
//        sleep();
        while (1){
                //TODO Auto-generated main function
                i=adc_read(ADC_CH0);
//                strcpy(vRAM, str_adcx); ltoa(&vRAM[5], i, 7); lcd_display(LCD_Line_ADCX, vRAM);
//                the following is for calibration purposes
                strcpy(vRAM, str_volt); ltoa(&vRAM[5], adc2_uv(i), 7); lcd_display(LCD_Line_ADCX, vRAM);
//                the following is for actual displaying, in 1/100th of C. so 4568C means 45.68C; -423C means -4.23C
                strcpy(vRAM, str_tempC); ltoa(&vRAM[5], uv2_tempC(adc2_uv(i)), 7); lcd_display(LCD_Line_Temp, vRAM);
                delay_ms(DLY_main_loop);                        //delay some time
        }
}


=============end of code====================

you will need to do a few things to make it work.

1) specify Vref. now, it is specified at 2v. it should be whatever your vref source is.

2) caliberation: you should compile the code, and caliberate it at two temperatures: T0 and T1, both in C. I chose 0C (using ice and water mixture), and 100C (boiling water). Put the diode(s) into T0/T1, and see what the voltage reading is and put it into the code and recompile the code.

then you are done.

improvement opportunities:

1) the display of temperature is in 0.01C, but without the decimal point. you can rewrite the ltoa() to mitigate that.
2) you can also add multiple channels to it.

I will post the schmeatic later.

MARK。

here is the schematic: essentially a diode or a series of diodes powered by a current source.

the current source can be a jfet, or resistor (though psrr suffers).

now, only one sensor is sampled, on AN0. but you can easily change the code to sample more.



(原文件名:16F684 temp diode.PNG)