Now the derivative of the step function is an impulse which has an amplitude, A, equal to the
change in temperature. We assume that the time for the sensor to move through the interface is
short compared with the response time of the sensor, so relative to the sensor’s response time, the
change in temperature does look like a true step. Thus, we have a known input or forcing
function. If the sample interval, δt, is small compared with the response time of the sensor, then
we can resolve the sensor's response which looks a bit more like a slow ramp, rather than a step.
Hence, with a known input, and a measure of the output as a function to time, y(t), we can
calculate the response function. From the definition of the convolution product we have