It is, I believe, well known that the Logic 8 gets warm while it is powered up. I have noticed that the readings I take when the unit is first plugged in differ somewhat from the readings I take later in the day.
I have a consistent source I am measuring, which produces a roughly 1 Hz output. The measurement I am performing consists of timing how long it takes 32 pulses to transpire. I wrote a Python script to interact with the Saleae API to capture one channel at 1,000,000 sps for 35 seconds, then measure the time between 32 pulses, starting and ending with a rising edge.
The following are actual readings taken in a single 75-minute session, but are typical for all sessions. If you plot these numbers, you will notice two things:
- there is an anomaly at 25 minutes, which I think we can ignore for this discussion, and
- the measurements tend to stabilize after about 30 to 35 minutes of runtime.
So, my two questions are:
- Is there a published warm-up period for the Logic 8 Red, and if not, is 30 minutes a reasonable value?
- Would one of the Logic Pro devices have a more consistent performance over time without requiring a warm-up period, or perhaps a shorter warm-up period?
Oh wow, thanks so much for the detailed observation on that. Logic 8 is in fact known to warm up more than our other devices as mentioned in the below support article (and as you’ve pointed out that it’s a well known topic for you).
Long story short, we unfortunately don’t have a public specification for this behavior. Devices are one-time calibrated at room temperature, and we haven’t characterized the devices at more than one temperature.
Based on the tests you’ve run, it does seem to stabilize after about 30min of runtime, and also sounds quite reasonable to us having not tested nor characterized this behavior.
For Logic Pro 8/16, we employ a power saving mechanism, such that when the device is not actively sampling, the current consumption is significantly reduced to the point where the device should remain or return to room temperature between captures. These devices should only get warm after a long capture.
So, given that information, our Pro devices might be more susceptible to varying temperatures (long captures will sustain higher temperatures, and shorter captures will sustain lower temperatures since the current consumption is reduced while it’s not actively capturing), and therefore, it may affect measurement readings based on the temperature of the device at that time.
On the other hand, Logic 8 will keep it’s temperature whether it captures or not, as long as it’s connected to the PC/software for a set period of time (say 30 min as per your observations), since it doesn’t have the same power saving mechanism as our Pro models.
Thanks for the response. Great observation that the Logic 8’s temperature would tend to be more consistent after the warm-up period regardless of the length of capture or duration of time between subsequent captures. For consistency, we will work with the warm-up characteristic of the Logic 8 rather than transitioning to the Pro version for this application.