Oscilliscope Seconds of Waveform Recording Capability Question - Page 1
Forum section: electronics / testgear

author: Silver_Is_Money
author_rank: Regular Contributor
timestamp: December 25, 2023, 02:52:09 am
content: The spec sheet for the Hantek TO1154D tablet oscilloscope states that it has 8mpts of storage capacity. How does this translate into seconds of waveform recording capability. Would this mean that it records for 8 seconds from recording start to terminus? And if not, how many actual seconds of waveform recording can it capture for review?

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 25, 2023, 09:00:58 am
content: Please search for it on the Internet before you ask, Google "memory depth sample rate" usually throws up good results with examples.You will get an answer to your question faster.The answer to your question is complex and depends on many settings.Am I right that you are about to buy your first scope?

author: Someone
author_rank: Super Contributor
timestamp: December 25, 2023, 10:07:22 am
content: https://www.tek.com/en/documents/primer/evaluating-oscilloscopes

author: Silver_Is_Money
author_rank: Regular Contributor
timestamp: December 25, 2023, 01:12:04 pm
content: Quote from: Someone on December 25, 2023, 10:07:22 amThank you! Time Duration of Waveform Recording = Record Length/Sample RateSo if a scope advertises a 250 Msa/S sampling rate and an 8M record length:8/250 = 0.032 seconds (or 32 ms) worth of record length being recorded for review.Would this be correct?

author: Fungus
author_rank: Super Contributor
timestamp: December 25, 2023, 07:51:45 pm
content: Quote from: Silver_Is_Money on December 25, 2023, 01:12:04 pmYes.But... on many 'scopes you can reduce the sample rate to get more time.eg. If a 'scope lets you reduce the rate to 1Msa/sec then you can record for 8 seconds.

author: Silver_Is_Money
author_rank: Regular Contributor
timestamp: December 26, 2023, 12:03:07 am
content: Quote from: Fungus on December 25, 2023, 07:51:45 pmThat's great to know. But I'm trying to record a DC voltage spike event that will only last for about 1.8 ms from start to finish, and capture it in fine detail. With the critical voltage rise peak occurring at about 0.25 ms after triggering, and with peak rise lasting for only about 0.02 ms. Or in other words, the most critical capture range will occur at between 0.24 and 0.26 ms post triggering on rise.

author: adam4521
author_rank: Regular Contributor
timestamp: December 26, 2023, 11:03:31 am
content: Most oscilloscopes have timebase detents in a 1-2-5 time sequence, calibrated 'per division' of horizontal display space, with ten or more horizontal divisions visible. So you will set it up for 0.5ms/div, to capture 5ms of time (ie your whole DC spike event). The oscilloscope can 'spread' its memory over that time, by changing the sample rate. This is manual or automatic, depending on brand and settings. This is why having more sample memory maintains higher sample rate for longer captures. You might want to delve deeper into the Hantek specifications -- sometimes products can have a high 'banner' spec but actually default to shorter memory for regular use -- I guess it is a responsiveness trade-off.

author: egonotto
author_rank: Super Contributor
timestamp: December 26, 2023, 11:06:04 am
content: Hello,many scopes have segmented memory for this. If you choose 500 us/div and 10 kS memory with the DHO1074, you can capture over 10000 events.Best regardsegonottoPS.: Sorry, I overlooked the fact that it's the Hantek TO1154D that doesn't have segmented memory.

author: Silver_Is_Money
author_rank: Regular Contributor
timestamp: December 26, 2023, 11:26:09 am
content: Quote from: adam4521 on December 26, 2023, 11:03:31 amI thank you kindly for this excellent advice! So am I correct from this that if the scope was set to 0.2ms/div (presuming that it has this capability) the record would span 2ms of time and capture the entire 1.8ms event?

author: Silver_Is_Money
author_rank: Regular Contributor
timestamp: December 26, 2023, 11:39:24 am
content: Quote from: adam4521 on December 26, 2023, 11:03:31 amThis seems to be the relevant section of the specs for the Hantek I'm considering. Does this seem adequate?

author: csuhi17
author_rank: Frequent Contributor
timestamp: December 26, 2023, 12:58:45 pm
content: Quote from: Silver_Is_Money on December 25, 2023, 01:12:04 pmyes, if the time base is less than or equal to 32ms/14Div.that is, you set the time scale to 2ms or less.If it is larger, for example 1s/div, then 8M points will be recorded in the memory in the same way, but there will be a longer time interval between two sample points.The minimum time between two sample points is determined by 250MSa/S.By definition, at 1GSa/S, the distance between two sample points will be a quarter as large.Segmented memory will not be good for you because it can be used to compare repeated signals.For you, the event occurs once or rarely, which you want to see in very high resolution. If you want to compare the events, then I was wrong.