学而时习之（2）：单边sar adc测热电偶温度

一、温度测量

% the thermal resistor
clc ;
close all ;
clear ;
% input the temperature
temp_zoom=25 ; % normal temperature in clesius
abs_zero_temp=-273 ; ?selutely temperature in kailvin(K) 4668
keff=60/0.0293; ?--25
% keff=100/0.0463; 5--25
vt0=0.498;
temp=-35:1:125 ;
k=length(temp);
tempout=zeros(1,k);
for ii=1:k
temp_in(ii)=-35 (ii-1)*1;
tempout(ii)=tsensor(temp_in(ii),vt0,temp_zoom,keff);
end
subplot(1,2,1);
plot(temp_in,tempout,'r-');
hold on ;
plot(temp_in ,temp_in,'b ');
grid on ;
hold off;
legend('tempout','tempin');
subplot(1,2,2);
plot(temp_in,tempout-temp_in,'r-');
grid on ;
legend('delta temp');

二、tsensor 函数

function temperature=tsensor(temp_in,vt0,temp_ref,ktc1)
FS=2;
num=10 ;
vrefp=FS/2 ;
vrefn=0;
vref=FS/2 vrefn ;
lsb=FS/2^num ;
bits=zeros(num,1);
weight=zeros(num,1);
for ii=num:-1:1
weight(ii)=2^(ii-1) ;
end
%% temperature to voltage
keff1=0.002 ;% unit is V/K
keff2=0.0000004; %unit is V/K^2
res0=500 ; %ohm
tempka=temp_in-temp_ref; % temp shift
res_temp=res0.*( 1 tempka*keff1 tempka*tempka*keff2);
% test circuit converter temperature to voltage
vtest=vref*res_temp/(res_temp res0);
%% voltage to digtal
% sample
sample=vtest ;
if sample>vrefp
disp('input is out of max limit,the vout is clamp to vrefp!');
else if sample< vrefn
disp('input is out of min limit,the vout is clamp to vrefn!');
end
end
% conversion
dout=0 ;
for ii=num:-1:1
if sample>vref
bits(ii)=1 ;
sample=sample-vref ;
else
bits(ii)=0 ;
end
vref=vref/2 ;
dout=dout bits(ii)*weight(ii);
end

%% ideal
% dout=(dout-2^(num-1));
vout=dout*lsb ;
%% print the conversion data
% fprintf('vin=%4.4fV, dout=M,vout=%4.4fV,delta_v=%4.4fLSB,LSB=%4.4fmV\n', vtest,dout,vout,(vout-vtest)/lsb,lsb*1000);
% fprintf('tht keff= %4.4f Cesuis per LSB\n',ktc1*lsb);
temperature=ktc1*(vout-vt0) temp_ref;
end

三、 仿真结果