Author Topic: HP 54645A oscilloscope opinions?  (Read 868 times)

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Offline Axtman

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HP 54645A oscilloscope opinions?
« on: November 16, 2019, 07:20:17 pm »
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?
 

Online oPossum

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Re: HP 54645A oscilloscope opinions?
« Reply #1 on: November 16, 2019, 07:25:30 pm »
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.
 

Offline Alfons

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Re: HP 54645A oscilloscope opinions?
« Reply #2 on: November 16, 2019, 07:42:44 pm »
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.
 
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Offline edavid

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Re: HP 54645A oscilloscope opinions?
« Reply #3 on: November 16, 2019, 07:55:31 pm »
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.
« Last Edit: November 16, 2019, 08:12:13 pm by edavid »
 

Online shakalnokturn

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Re: HP 54645A oscilloscope opinions?
« Reply #4 on: November 16, 2019, 08:00:17 pm »
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...
 

Offline Stray Electron

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Re: HP 54645A oscilloscope opinions?
« Reply #5 on: November 17, 2019, 05:55:01 am »
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?

  100Mhz?  This isn't 1965 any more.  $200? I have bought several far better LeCroys for $35.
 

Offline David Hess

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Re: HP 54645A oscilloscope opinions?
« Reply #6 on: November 17, 2019, 07:14:49 am »
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.
 

Online oPossum

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Re: HP 54645A oscilloscope opinions?
« Reply #7 on: November 17, 2019, 05:58:19 pm »
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.
 

Offline Alfons

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Re: HP 54645A oscilloscope opinions?
« Reply #8 on: November 17, 2019, 06:11:33 pm »
Is ETS and Peak Detect (for Glitches) not a contradiction in terms? As far as I know, Peak-Detect requires RT sampling.

 

Offline David Hess

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Re: HP 54645A oscilloscope opinions?
« Reply #9 on: November 17, 2019, 07:08:07 pm »
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 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.

Quote
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.

I feel the same way about my Tektronix 2230/2232 and 2440.  A significantly better modern instrument is cost prohibitive.

Is ETS and Peak Detect (for Glitches) not a contradiction in terms? As far as I know, Peak-Detect requires RT sampling.

Peak 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.
« Last Edit: November 17, 2019, 07:13:30 pm by David Hess »
 

Offline vk6zgo

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Re: HP 54645A oscilloscope opinions?
« Reply #10 on: November 18, 2019, 04:20:13 am »
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?

You 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!
 

Offline 0culus

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Re: HP 54645A oscilloscope opinions?
« Reply #11 on: November 18, 2019, 05:11:18 am »
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?

You 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!

Yep, 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.
 

Offline george.b

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Re: HP 54645A oscilloscope opinions?
« Reply #12 on: November 18, 2019, 08:04:12 am »
$200 for a 200 MSa/s scope? I'm sure you can find better deals than that over there in the US.
 

Offline Labrat101

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Re: HP 54645A oscilloscope opinions?
« Reply #13 on: November 18, 2019, 07:32:26 pm »
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 .
« Last Edit: November 18, 2019, 07:57:35 pm by Labrat101 »
If it's Gets Hot its Working. If its Getting cold! it's your Coffee. @:-
 

Offline edavid

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Re: HP 54645A oscilloscope opinions?
« Reply #14 on: November 18, 2019, 07:58:36 pm »
And Sorry george .b your wrong it is 500Msa/s

It 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=eng

Quote
The Keysight 54645A 2-Channel 100-MHz deep memory and megazoom oscilloscope, 2ns/div sweep speed and 200 MSa/s acquisition, coupled with its unique high-speed display, gives you the view of your critical digital control signals needed to ensure proper circuit operation. In addition, the Keysight 54645A's very deep memory and 50-second/div sweep speed allow you to capture transducer and analog signals at a higher sampling speed at long timebase settings.

Often in mixed-signal systems the events of interest either take place over a long time span or they are widely separated from the trigger event. With 1 million samples per channel, Keysight's MegaZoom technology captures long time spans with a high sampling speed, allowing you to see the fine detail needed to solve elusive mixed-signal problems.

    Dual-channel 100-MHz scope with 200 MSa/s
    1 MB of memory per channel
    Keysight MegaZoom technology allows deep memory capture and a responsive display
    Simple, easy-to-use controls
    Glitch triggering
 
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Offline george.b

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Re: HP 54645A oscilloscope opinions?
« Reply #15 on: November 18, 2019, 08:06:20 pm »
Thanks, edavid, you beat me to it :)

So, 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.
 


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