how to plot with respect to time insted of samples

hello,

i have sensor which gives voltage output based on change in radiant temperature, the plot i am doing now is voltage signal in y axis and samples per trigger in x axis,

i want it to change the x axis to time.

plz anyone help.

[Walter Roberson]

How are you plotting against samples per trigger? That is normally a fixed quantity. Are you experimenting with changing the number of samples you gather at one time ?

[MANJUNATH]

number of samples are not being changed 1000 samples per trigger are considered

i am able to plotting the acquired voltage value against 1000 samples .i want the ploting for voltage v/s time.

Answer 1

[Lalit Patil]

 % Assign figure(1) to your V against samples program.. Then
 figure(2)
 V = your data
 T = 1:100 % specify time unit
 plot(T,V)

Answer 2

[Walter Roberson]

Ah, your current x axis is not samples per trigger: it is sample number within the buffer.

So change your code to keep track of the number of times you have previously sampled. Then if you know your sampling frequency FS in Hz, use

Previous_Triggers = 0;    %before loop

%in loop
t = (Previous_Triggers * Samples_Per_Trigger + (0:Samples_Per_Trigger-1)) ./ FS;
plot(t, V);
Previous_Triggers = Previous_Triggers + 1;

[Priya Venugopal]

How can i store the samples in the buffer

[Priya Venugopal]

pl help

[Walter Roberson]

@Priya Venugopal

When practical it is typically best to allocate a fixed-sized buffer, and to write new samples into it by indexing (and then increase the variable that indicates where to write to next.)

When you write into a fixed-sized buffer, then you have the advantage that you never need to spend time expanding the buffer as new data comes in -- which can be a fairly expensive operation of not coded correctly.

There are alternatives. For example in some cases you only need to retain a certain number of samples. The most efficient way to do that typically involves using a "circular buffer"