HP 54645A oscilloscope opinions? - Page 1
Forum section: electronics / testgear

author: Axtman
author_rank: Regular Contributor
timestamp: November 16, 2019, 07:20:17 pm
content: I have a chance to buy a used Hewlett Packard 54645A oscilloscope for $200. I already have a few analog scopes but occasionally would like to accurately measure P-P voltage and frequency.What do you think of this scope?

author: oPossum
author_rank: Super Contributor
timestamp: November 16, 2019, 07:25:30 pm
content: Price is a bit high. You can get the improved successor 64622A on eBay for less. Even the mixed signal 54622D can be had for less if you are patient.Keep in mind these are 20+ years old. Still useful, but could be a loss if it fails soon after purchase.

author: Alfons
author_rank: Regular Contributor
timestamp: November 16, 2019, 07:42:44 pm
content: In Germany, prices for used equipment are much higher than for you across the Atlantic. But for this price we also find old LeCroy devices with much better features.

author: edavid
author_rank: Super Contributor
timestamp: November 16, 2019, 07:55:31 pm
content: It has a low sample rate, not very deep memory, and monochrome display with no intensity grading, so $200 is too much. You would be much better off spending ~$300 on an Instek GDS-1054B.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 16, 2019, 08:00:17 pm
content: Not that bad for the price, although I'd expect cheaper in the US.It depends what you'll be using if for, the 1M memory is not bad but 200MS/s can soon be a limitation.With a little patience you should be able to find a LeCroy 9354M or L. Yes, I'm biased...

author: Stray Electron
author_rank: Super Contributor
timestamp: November 17, 2019, 05:55:01 am
content: Quote from: Axtman on November 16, 2019, 07:20:17 pm100Mhz? This isn't 1965 any more. $200? I have bought several far better LeCroys for $35.

author: David Hess
author_rank: Super Contributor
timestamp: November 17, 2019, 07:14:49 am
content: It is 200 MSamples/second and supports 5 nanosecond peak detection so I would have no complaints. I usually get by with a Tektronix 2232 which has half the sample rate with peak detection just fine.I think these are the CRT DSOs where HP doubled the horizontal display resolution so the display should look pretty good.

author: oPossum
author_rank: Super Contributor
timestamp: November 17, 2019, 05:58:19 pm
content: They do ETS at the fastest timebase settings, so the effective sample rate is higher than 200 MSps. Peak detect works well and is sometimes very useful. They can catch stuff that the Tek DSOs with CCD will miss.I have the 54645D and 54622D and have considered buying something new several times. I haven't done that because these old DSOs have been able to do everything I needed. The quality problems with Rigol and Keysight have also been a deterrent.

author: Alfons
author_rank: Regular Contributor
timestamp: November 17, 2019, 06:11:33 pm
content: Is ETS and Peak Detect (for Glitches) not a contradiction in terms? As far as I know, Peak-Detect requires RT sampling.

author: David Hess
author_rank: Super Contributor
timestamp: November 17, 2019, 07:08:07 pm
content: Quote from: oPossum on November 17, 2019, 05:58:19 pmI do not consider ETS to be a disadvantage. The maximum ETS sample rate of the HP 54645A is apparently 25 GSamples/second.Many of the early and late Tektronix CCD based oscilloscopes support peak detection.QuoteI feel the same way about my Tektronix 2230/2232 and 2440. A significantly better modern instrument is cost prohibitive.Quote from: Alfons on November 17, 2019, 06:11:33 pmPeak detection does not apply in ETS mode. Peak detection allows the maximum sample rate to be used at slower time/div settings where sample rate is limited by the acquisition record length.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 18, 2019, 04:20:13 am
content: Quote from: Axtman on November 16, 2019, 07:20:17 pmYou can get an accurate frequency measurement if your analog scope has a vertical amp output available on the back panel.Just hang a real frequency counter off that!

author: 0culus
author_rank: Super Contributor
timestamp: November 18, 2019, 05:11:18 am
content: Quote from: vk6zgo on November 18, 2019, 04:20:13 amYep, this is what I did. I got a nice compact HP 5385A for dirt cheap at a hamfest and put it on top of my 7904A (which incidentally has the outputs on the front panel). Adjusted the counter timebase to agree with my GPSDO and it works great.

author: george.b
author_rank: Frequent Contributor
timestamp: November 18, 2019, 08:04:12 am
content: $200 for a 200 MSa/s scope? I'm sure you can find better deals than that over there in the US.

author: Labrat101
author_rank: Unknown
timestamp: November 18, 2019, 07:32:26 pm
content: Hi have one of these in my lab I bought about a year ago . Best value for money its a great scope and will nock spots of the digitals.the only thing you will have to do is replace the nvam batteries they are mounted inside the chip case and are easy to replace .either replace the chip . .. I used a small drimel and cut the battery out and soldered a new lithium 3.2v button . little fiddly takes half an hour . And then do the Calibration . and if it comes with the maths plug on the back it will give you FFT and a few other must haves. and that also has nvam battery that has to be replaced as well.I love this scope . , Make sure that the screen is not damaged due to over bright. .I also have some of the sevice manuals .And Sorry george .b your wrong it is 500Msa/s and the frequence is good to .001 after calubration easy to do ..follow the on screen instructions and need a 100khz to 1Mhz square wave sig generator . and some bnc cables & T .

author: edavid
author_rank: Super Contributor
timestamp: November 18, 2019, 07:58:36 pm
content: Quote from: Labrat101 on November 18, 2019, 07:32:26 pmIt certainly is not. Here are the specs straight from Keysight:https://www.keysight.com/en/pd-1000001437%3Aepsg%3Apro-pn-54645A/2-channel-100mhz-deep-memory-megazoom-oscilloscope?cc=US&lc=engQuote

author: george.b
author_rank: Frequent Contributor
timestamp: November 18, 2019, 08:06:20 pm
content: Thanks, edavid, you beat me to itSo, yeah, as the specs say, 200MSa/s. That is just Nyquist-sufficient for a 100MHz sine wave in real-time acquisition. I don't imagine it'd be terribly useful for any real-life signals above 50MHz or thereabouts, as opposed to a 500MSa/s scope, which would actually be useful for 100MHz. Whether 200MSa/s are sufficient for OP's needs, I don't know, but for $200 I think there are probably better deals around.