# Downsampling from 100Hz to 60 Hz

I have two sensors measuring a single time varying signal . The first sensor (reference sensor) is sampling the data at 60 Hz and the second sensor (test sensor) is sampling the data at 60 Hz. I need to check the accuracy of the test sensor by comparing with the reference sensor. I am confused about how to downsample the data recorded at 100 Hz to 60 Hz. I see it is quite trivial to downsample from 100 Hz to 50Hz/25 Hz. But I am confused how to downsize to 60 Hz.

After downsampling, is cross-correlation a good technique to compare the data from two sensors?

Thanks, Peter

• Downsampling by an integer factor might seem evident, but it is not trivial and requires care, as much as downsampling to another frequency. Wouldn't your consider upsampling both to, say, 300 Hz? And what is you criterion to tell a signal is good? – Laurent Duval May 20 '18 at 20:55
• @Andrea you've got a small math problem: as Laurent said, you want to oversample threefold to 300 Hz and then downsample 5× to 60 Hz (you got the factors the wrong way around) – Marcus Müller Jun 20 '18 at 13:29
• I don't quite understand the problem: Do both sensors actually have the same sampling rate of $60\,\text{Hz}$? – applesoup Jun 20 '18 at 13:31
• I assume he must mean one sensor is sampling at 100Hz. If so as Marcus alluded upsampling the 100 MHz with a x3 interpolator and then decimating by 5 to get that signal at 60 Hz makes sense. Nothing needs to be done to the signal already at 60Hz. Assuming the reference sensor is “known good” then yes correlation of the two once at the same rate make perfect sense. Specifically computing the correlation coefficient would give a quality metric of the result. If both sensors have unknown quality, correlation will not provide useful information. – Dan Boschen Sep 22 '18 at 18:04