# Start Time Missmatch - Analog vs. Digital channel in Raw export ?! **URL:** \ **Category:** Logic 2 Software\ **Created:** [June 30, 2025, 12:31pm UTC](https://discuss.saleae.com/t/start-time-missmatch-analog-vs-digital-channel-in-raw-export/3456 "2025-06-30T12:31:44Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![a.scheunemann](https://avatars.discourse-cdn.com/v4/letter/a/e9a140/32.png) [@a.scheunemann](https://discuss.saleae.com/u/a.scheunemann)\ **Post date:** [June 30, 2025, 12:31pm UTC](https://discuss.saleae.com/t/start-time-missmatch-analog-vs-digital-channel-in-raw-export/3456/1 "2025-06-30T12:31:44Z")
I have tried to use digital trigger to align analog measurement and noticed high difference some how the start time and relativ difference in the raw export is not matching between the digital and the analog channels - only in the raw export. If I zero reset both recordings assume that analog and digital are starting at the same time ignoring the start time meta info, the records seem to match better but hard to say if its correct !? Anything know about it? ---
**Author:** ![a.scheunemann](https://avatars.discourse-cdn.com/v4/letter/a/e9a140/32.png) [@a.scheunemann](https://discuss.saleae.com/u/a.scheunemann)\ **Post date:** [July 1, 2025, 8:10am UTC](https://discuss.saleae.com/t/start-time-missmatch-analog-vs-digital-channel-in-raw-export/3456/2 "2025-07-01T08:10:47Z")
analog\_0.bin:0 tstart=5.452571 analog\_13.bin:13 tstart=5.452571 analog\_2.bin:2 tstart=5.452571 analog\_3.bin:3 tstart=5.452571 digital\_7.bin:8 tstart=5.452649 digital\_9.bin:10 tstart=5.452649 this is systematic I guess it must have something to do with the first sample time but makes no sense still I could not find something about it in manual - might be that I am blind … using Version: 2.4.29 of Logic and the Pro 16 ---
**Author:** ![BitBob](https://yyz2.discourse-cdn.com/flex030/user_avatar/discuss.saleae.com/bitbob/32/2292_2.png) [@BitBob](https://discuss.saleae.com/u/BitBob)\ **Post date:** [July 1, 2025, 4:05pm UTC](https://discuss.saleae.com/t/start-time-missmatch-analog-vs-digital-channel-in-raw-export/3456/3 "2025-07-01T16:05:08Z")
See another post about analog filtering details: > [@Saleae Logic2 Analog filtering technical details?](https://discuss.saleae.com/t/saleae-logic2-analog-filtering-technical-details/2427/9): > > Hi @BitBob, I’m glad you’re interested! I’ve emailed you a copy of your device’s factory test data. You can try plotting that on a log/log graph to see that frequency response effect I was talking about, which is why we include a calibration filter in the calibration file. After reviewing your posts, I think I can cover all of your questions with the following background information. Why we don’t plan to add down sampling AA filters again for future analog products. To clarify, future analog … … specifically, about the **group delay** feature. You can look at your device-specific calibration file to see how your setup is calibrated. Ultimately, it is trying to ‘re-time’ the analog (filtered) data with the digital data streams due to extra latency caused by the various filters (hardware & software) and other delays (ADC sampling/conversion, etc.) Basically, a digital read is ‘faster’ and more ‘real-time’ than an analog reading. There is more signal processing hardware and post-processing software steps on the analog samples which will lag behind the timeline of the digital sample captures. Thus, a simple step function (i.e., change from 0V to 5V ‘instantly’) needs to be ‘synchronized’ between analog vs. digital display so they still appear to transition at the same ‘time’ in the waveform display (see `mGroupDelay` parameter in calibration file). I assume the ‘raw’ captured data is just the samples, without the group delay timing offset taken into account. Therefore, I suspect the meta data / start timestamps are needed to compare between channel timelines. ---
**Author:** ![a.scheunemann](https://avatars.discourse-cdn.com/v4/letter/a/e9a140/32.png) [@a.scheunemann](https://discuss.saleae.com/u/a.scheunemann)\ **Post date:** [July 2, 2025, 7:42am UTC](https://discuss.saleae.com/t/start-time-missmatch-analog-vs-digital-channel-in-raw-export/3456/4 "2025-07-02T07:42:17Z")
Problem though if I replot the readout respecting the meta data start times the data seems misaligned between Digital and analog to realty. For this purpose I just recorded Anaolg and digital on a step function in saleae and with oscilloscope. If I then ignore the start time thereby shift the analog backwards in time the alignment is much better to what is expected… and then the plottet picture using the raw data looks also much more like the one in the Logic Tool so something must be of here or misunderstood by me. Your comments about the calibration file are interesting, I had a look but I do not understand yet need some more time to get into it … . Regardless thanks for the explanation and awareness point of all the analog sampling magic that has to be taking in account. Even though I am not 100% sure, but I still thing I am onto something that ether needs fixing or a better explanation.