Single Sequence on Analog Scope - Page 1
Forum section: electronics / beginners

author: hololight
author_rank: Newbie
timestamp: November 24, 2012, 02:56:50 pm
content: So I have advanced in my electronics hobby to the point of picking up a used scope. I found a Tektronix TAS 465 at a good price and went with it. I am very much liking it so far. But while reading the manual I found a feature that seems rather common on analog scopes (and is always on digital), that confuses me....Single Sequence. I understand its use on a DSO, but on my analog scope it just triggers and flashes a waveform for a second and its gone. What is the use of that?Chris

author: Unknown
author_rank: Unknown
timestamp: November 24, 2012, 03:14:12 pm
content: Scope camera. People would attach a special dedicated camera with Polaroid film to the CRT. The scope would trigger the camera as soon as the sweep started, and the phosphor would glow for long enough to expose the film. You could get CRT with different phosphor colors and persistence times to optimize for camera use. In theory you could do the same with a digital camera, but triggering it in time would be tricky, most are quite slow to respond to a shutter release.

author: jeroen74
author_rank: Frequent Contributor
timestamp: November 24, 2012, 03:32:57 pm
content: You could do it with a digital camera, most DSLRs feature a bulb-mode that keeps the shutter open for as long as you wish. With crazy high ISOs these days it shouldn't be difficult to capture the trace.

author: T4P
author_rank: Super Contributor
timestamp: November 24, 2012, 04:16:06 pm
content: Quote from: jeroen74 on November 24, 2012, 03:32:57 pmWait. Shutter opened longer = brighter and Higher ISOs are for better sensitivity so just turn the ISO down to 50 as well as turn up the F-stop to the maxEDIT: Oh i realized it's about hourly ns pulses. Nevermind. Best way is to send a DSLR to ISO 12,800 (Hi2 mode on my D3100) F-stop to 1.4 with a pancake lens and Bulb mode. Oh and do it with night with ALL the lights off

author: Unknown
author_rank: Unknown
timestamp: November 24, 2012, 05:39:38 pm
content: Good luck with that. Phosphor decay might be in the orders of microseconds to milliseconds. How much signal will the camera register from a dim CRT in that time? For single shot, they used lenses with apertures up to f/1.2 and film speeds up to ISO 20,000. This will cause issues with bulb mode, however, that film would probably be overexposed from ambient light and graticule illumination before you could trigger the scope. Bulb mode might be ok for slow signals that occur frequently, but not for ns pulses that might occur once every few hours.

author: w2aew
author_rank: Super Contributor
timestamp: November 24, 2012, 05:43:07 pm
content: Quote from: alm on November 24, 2012, 03:14:12 pmThe dedicated scope cameras that would 'hang' on the face of the CRT would create a light-sealed environment. With experience, you'd learn how bright/dim to make the graticule, readouts and trace intensity for a good exposure. The camera had a viewing port that you could open to setup the scope. Then, the most common thing was to open the shutter manually or on a few second timer, and trigger the single shot to get the exposure.Ahh, the days before digital storage.

author: BravoV
author_rank: Super Contributor
timestamp: November 24, 2012, 06:37:27 pm
content: Quote from: alm on November 24, 2012, 05:39:38 pmAgree, its not easy and mostly it will fail if the "blip" is too fast for your camera to capture even in perfectly dark room and with the graticule illumination turned off.Example my setup below, using the camera's remote to take the shot of a steady repeating signal only at my 400Mhz analog scope, not for capturing single shot, while for that I used my cheap dso.I have a sealed room from external light, and with this remote is quite handy since I have the room's lightning switch within my arm's reach. So to start taking shot, the sequence is turn off room light and it will be totally pitch dark, press the camera's remote to open the shutter, once finished, turn on the room light again to prevent me from knocking out things around in the dark.PS : This picture is originated my other post from other thread discussing how to capture a good repeating signal at analog scope ->w2aew's excellent scope training thread

author: mazurov
author_rank: Frequent Contributor
timestamp: November 24, 2012, 07:51:32 pm
content: That's what I made a while ago to take pictures of my 7104. It is C53 scope camera bought on eBay for pennies, gutted and modified to mount Canon A640 P&S. Works very well and also fits my 7904a with ultra-fast (and 2x smaller in each direction ) CRT.