I asked Labradar about the accuracy of that calculated number, was told that there is no error in that number.
After working with my Labradar for a few sessions, I realized that the muzzle velocity number was calculated rather than measured. I asked Labradar about the accuracy of that calculated number, was told that there is no error in that number. (note - I am just relating what I was told.)
"Calculated" and "no error" don't work together. I appreciate the research into accuracy here. I've downloaded the file and when I have a chance to look closely, I intend to. I'm a fan of the LabRadar and an even bigger fan of refining it further. Thanks.
I suspect you are right, Long BomberWhat is the biggest variance that you have seen between the labradar data and the excel calculated velocity?
I have run mine through something much simpler running through an pivot chart, not kicking out the outlier readings, I have only done this on about twenty shot strings, with around 120 shots total, somewhere around 70% of the shots are within 1 fps, almost all within 2, and I don't remember any over 5fps. Now if I had pulled out those outliers maybe the change would be larger?
Excel and large data sets are a big part of my living. The LabRadar's ability to generate data was one of the prime reasons I purchased one. I'm not sure what triggered me to really investigate the calculations, but it was probably one of those readings we all see, like example 1 in my first post. A ludicrous V0, with subsequent distances being more believable. With the tracking files, it was easy enough to investigate what was going on.Entoptics: I'm fascinated by what you've discovered, and curious about how it came about? (you don't have to answer that question.)...
I wonder if those first-collected data points would be better numbers if the Labradar was triggered by an external accelerometer trigger (i.e., not a microphone trigger), such as by Piet or JKL Precision.
The Labradar would probably be triggered a little sooner by the accelerometer, which may give the circuitry a little more time to stabilize before seeing the bullet and collecting the first data points.
What is the biggest variance that you have seen between the labradar data and the excel calculated velocity?
See the first example in my first post. That one was off by about 4800 fps. Generally though, 9 outa 10 shots are within 5 fps of the Excel regression, and 8 outa 10 are within 2 fps.
If you take a look at my OP, you'll see a table with the last few load tests I did. I took the raw output from the LabRadar, then ran the same shots through my spreadsheet. You can see that in 4 outa 5 cases, the ES/SD of the LabRadar was more than the regressed velocities, and in some cases substantially so.
In my opinion, it's a problem with enough of the data, that for important work, I run every shot through the spreadsheet. If I'm just trying to get an idea how fast Tula 556 is going in my AR, I shoot 15 rounds and consider the average just fine. When developing a load for potential extended range work, with only 3-4 rounds per recipe, getting one bad reading by 5 fps can muck up the statistics pretty significantly.