Showing of early digital scope capabilities: Philips PM3305 - Page 1
Forum section: electronics / general

author: jancumps
author_rank: Unknown
timestamp: August 22, 2014, 12:44:55 pm
content: I've taken this photo to show the state of digital scope technology in the mid 80s.The PM3305 has memory for a whopping 4096 8-bit samples. On the picture below the screen shows 8 signals.4 lower signals are showing real time, 512 samples each. The 4 top signals are displayed from mem, and are 512 samples each too.It is all a bit humble these days, but for its time this was rather decent (and expensive) equipment.

author: tom66
author_rank: Super Contributor
timestamp: August 22, 2014, 01:38:24 pm
content: Well, 4K of sample RAM is better than Tek's current offering of 2.5kpoint on the Tek Basic Scope range! How fast can the scope sample in digital mode?

author: jancumps
author_rank: Unknown
timestamp: August 22, 2014, 02:10:00 pm
content: It always samples one full screen. The fastest it can sample real-time is 200 microseconds per division. There are 10 divisions. And 4096 samples in single signal mode. My not to be trusted math gives up here.I think 2.048.000 HzIn repeat mode (the dodgy sequential sampling method) it works up to 0.1 microseconds per division

author: nctnico
author_rank: Super Contributor
timestamp: August 22, 2014, 02:25:06 pm
content: This scope reminds me of my good old Tektronix 2230 which had 4k sampling memory and 10Ms/s sampling speed. The 4k sampling memory allowed to use it for debugging I2C and SPI problems.

author: David Hess
author_rank: Super Contributor
timestamp: August 22, 2014, 03:32:21 pm
content: One difference when compared to a modern low record length DSO is that the sample memory is usually divided between all channels. The 2230 and 2232 support a 4k record length with 1 channel and a 2k record length with 2 channels and those are halved again if peak detection is used.As a practical matter though, even using the 2230 and 2232 with a 1k record length divided between 2 channels and using peak detection for a real record length of 250 is not objectionable. You have to look closely to even notice the loss of resolution because the vector CRT display has such a high resolution to start with. I hardly notice.The contemporary 2440 series did not have this record length limitation and they operate much more like a modern DSO with a short record length. They support a 1k record length on each channel individually of which the display shows half at any one time so 50 points per horizontal division which is high resolution even by today's standards.The 2230 and 2232 with a 4k record length display 1/4 of the record on the display at a time (the multifunction control acts to scroll) and have a special "compress" mode if you want to see the whole thing at once.

author: marshallh
author_rank: Unknown
timestamp: August 22, 2014, 08:16:50 pm
content: Still beats a TDS220 iirc.

author: nctnico
author_rank: Super Contributor
timestamp: August 23, 2014, 12:08:40 am
content: Quote from: marshallh on August 22, 2014, 08:16:50 pmOfcourse it does!Mentioning a TDS210 makes me want to use the barf 'smiley' which is not available on this forum!

author: jancumps
author_rank: Unknown
timestamp: September 27, 2014, 12:14:18 am
content: I've sold this one now, to an engineer who needs 3 channels to measure motor steering circuits.I've had it since September 2012 and enjoyed it a lot. As a Philips and test gear fan boy, it's always odd to let something go.I've been fixing the small troubles that it had after 25 years. I bet it'll run another 25 without problems.