Electronic multimeters and oscilloscopes

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BlueSkyNick

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Anybody used a multimeter with RS232 output?

Things have moved on since I was taught how to use an AVO8 as a very helpful piece of test equipment. Fluke had just started selling Digital Multimeters but not at 'joe public' prices.

Three decades later I need to do some testing on my Autohelm to help Raymarine work out what is wrong with it without me having to send it back yet again. Put a digital multimeter on the output and look for the pulses they say. I dont know what voltage or pulse rate I am looking for, until I see it !!

My cheap and nasty analogue multimeter is not sensitive enough, and a second option would have been to borrow a osillyscope but cant find one.

So I have been looking at buying a reasonable DMM, and have foundTHIS ONE at Maplins.

For 30quid it looks pretty good, especially as it has a RS232 output and some software to put in the laptop. Only trouble is, it doesnt tell you what the software does for a living /forums/images/graemlins/confused.gif

I am wondering if it will provide me with a graphical image of what ever I am measuring, so if I am looking at pulsed DC, I will see the peak voltage and pulse rate.

The more expensive option is a handheld scope for around £100 on Ebay from HongKong, but a bit excessive just to test the autohelm - I could pay somebody else to come and do it for that price.

EDIT: Oops, now I have made the effort to go to the Uni-Trend website HERE and download the software with manual, it seems to do the trick. Would still appreciate any useful comments though.
 
It looks like a nice bit of kit at that price. The manufacturers website is at http://www.uni-trend.com/UT60A.html and you can download the manual and software. I have had a very quick look at the manual but I think that if you download the software as well you'll get a good idea of what it can do.

Mind you, I am surprised that Raymarine would expect you to take measurements that require data logging equipment like that? However, it could be hugely useful for finding intermittent faults.

For £25 you get a multimeter with a good spec (I don't know if it's a good multimeter, of course) and a data logger that might be handy. Maplins used to sell scope interfaces to PCs but the last time I checked they'd stopped doing them - shame, as I was about to buy one.
 
If you go for a DMM, make sure it has a bar-graph function along the bottom of the display screen. Even if you cannot "see" the pulses on the numerical display, the bar-graph will show the pulsing.

I've got an oldish Fluke with bar-graph, and a small pocket DMM also with bar-graph. Invaluable
 
Hi David,

per my edit I have checked the website and downloaded the software - it does give a graphical representation over time but the sampling rate is 1 second minimum. Philip's suggestion of a flashing bar is good, and I will keep looking for alternatives.

Cut a very long story short, the autohelm packed up in Raz du Sein on a broad reach with 4kts of tide up the chuff !! We have been hand steering ever since.

There was a mechanical failure which we had fixed but still problems. Sent the black box to Raymarine, and they replaced the output FETs and one or two other bits - still giving me problems. So rather than me send it back at my cost and risk them charging £60 to insist there is nothing wrong, I have gone into self-testing mode following their advice. Once I have proven it is still the box, I will either send it back under their repair warranty or buy another 2nd hand - another forumite has offered one for sale.

We were busy every weekend in the run up to Christmas, but now have SWMBO's agreement to work on boat one day per weekend ! /forums/images/graemlins/smile.gif

Happy New Year to all in Almerimar - please onpass regards to Spencer and Mike.
 
As an Electronics Engineer Ive always used a Fluke, not cheap but certainly does the job.

I have now found a great digital meter at a decent price that I use on the boat and keep one at home. I bought it from Argos and it costs £24.99 (Code 7015603), great piece of gear. Can also test diodes, transistors etc. Also has a temperature probe.

http://www.argos.co.uk/webapp/wcs/stores...rms=MULITIMETER

Cheers

Steve B
 
I bought a digi multimeter from maplins with an RS232 output ..... not sure if it is the same model that you have found (it's on the boat). It works fine connected to my laptop via an RS232 to USB converter. I use it for doing battery discharge tests and only sample every 15 mins!! I can't remember the minimum sampling time but I think for checking any sort of pulsed output you will be struggling with a multimeter and really need a scope of some sort.
You can get data acquisition cards which you plug into your PC and then with the appropriate software you can use your PC as a scope. I have seen professional versions of this (Labview for example) but have no idea if there are cheap Chinese copies around ?????? could be worth a check .......... and if you do find something perhaps you would let me know as I would also be interested.

Alan.

P.S. Did a quick check and found this:
USB-9812-10V Low Cost USB DAQ Module with 8 SE A/I, 2 A/O, 12-bit res., 8 D/IN, 8 D/OUT, 1 16-bit Counter/Timer, +/-10V input range ... more »
$349.00
 
I see that someone is offering one on Ebay for £90 from an Ebayer in China. Where did you get yours from? Can it really get all its power from the USB?

Have you tried the FFT yet?/

Postage is £22 to anywhere in the world. Is that a good deal or should I look for a different Yuan?
 
Hello David, yes the FFT is amazing, the save and recall are superb too. the power is similar to the older external hdd's, 2 connectors to usb. no probs.

giorgio11185 is the seller I used on Ebay, had it shipped directly to the boat. Even the probes are excellent quality.

I think it was 110 gbp delivered to the boat. only took about a week.

got a super 2.4 ghz freq counter too from China, 30 squids, also good kit. my sig gen is a usb dds unit from Australia with a external second hand mil spec 110 db step attenuator and a programmable attenuator on board, good for 60 Mhz, but works well on harmonics.

Joe
 
I have one of those - and I think its the one with the RS232 output. I can check and if it does, you're welcome to borrow it.

Rick
 
Thanks Joe, and Nick, I'll look into that /forums/images/graemlins/smile.gif
 
No Probs David, the only thing to bear in mind is it is 8 bit resolution, as are most low end dso's.. otherwise it is perfect for my use.. I wouldnt like to use it on high end tube audio lol.. but, for instance, the fft allows me to take sinad readings which replaces my old sinadder which was one piece of equipment I missed.
A lot of kit for a 100 squids, not as good as my old tektronix, but much much less real estate and more features.
Joe
 
Does it look very steppy (staircase-like) or do they interpolate between points?
 
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