What does "TRUE RMS" mean?

About that:

Hi Paul,

HP3458A has 0.01% best accuracy 1Hz-10MHz.

--

John Devereux

Except they are called Agilent now.

Here's how to fix a broken Keithley 2100:

ftp://jjlarkin.lmi.net/KeithleyFix.jpg

John

HP is still called "HP" .

John

I've never used one of those. What's the problem you had with it?

I bought four of them. One failed, and the other three were immensely annoying. They power up at something like 60 updates per second, unreadable, and it takes a zillion keypresses to slow it down. And that particular setting can't be saved. And other bugs.

The one in the pic powered up that way and never did anything else.

The 2100 isn't a Keithley, it's a Chinese rebrand

which is sold all around the world with multiple rebrands. Array offered to do a rebrand version for us, too.

I complained so much that Keithley took them back and gave me 2000s.

John

This is the only HP that's currently worth buying:

Their printers are good. I finally retired my 6Ps after many years, and cut over to CP1525 color lasers. They installed easily and work great. They *should* come with a free flashlight so you can read the LCD.

Most of our computers here are ProLiant server boxes with hot-plug RAID on the front panel and redundant power supplies, fans, and BIOS. They have been wonderfully reliable.

John

There are some on eBay for $600-$800. Might be a good investment.

That also looks quite good, and are available on eBay for as little as = $200=20 to $400 (but some are $1000). If the $200 unit is OK (and it is = described as=20 working), that may be the best deal. At least HP/Agilent usually have=20 extensive schematics and cal/repair documentation.

Thanks!

Paul=20

So they were sold by Keithley? How much do they cost?

Paul

Yes, but I can't really justify / afford $4500 or more.

Thanks!

Paul=20

We have a 34401A. It's OK, but the VF display kicks a lot of noise out the front-panel connectors. Somewhere around a millivolt on the AC range, the reading drops to zero, which is probably a workaround to hide the display noise.

I really like my Fluke 8845A.

John

Check their web site. I think they still sell it.

John

It has a one year accuracy of 0.06% RDG + 0.04% RNG on the 100mV scale. = So=20 for my 5 mV signal it would be 0.06% + 0.0004*100/5 =3D 0.86% RDG. Not = bad,=20 but not great. There is one on eBay for about $1000 and an 8846a not = working=20 for about $500.

I need to figure out the real accuracy of the others I was considering. = But=20 maybe it would be better to use a 100A 100mV shunt for my low-end=20 calibration. Then I would have a full 50 mV to work with. Just a hassle = to=20 change the shunt, but I could probably rig them up in series and just = use a=20 high current switch (like a battery cut-off) or a jumper to short out = the=20

100A shunt when I calibrate at higher currents (500-1000A).

Paul=20

Or just factor it in. Nahhhh...

Make the shorting bar out of Silver stock. Clamp it in tightly.

Are you measuring AC or DC? Both are a nuisance to measure accurately if you use a shunt.

These are phenomenal:

John

"John Larkin"

** So is the price at over $800.

Very nearly the same for les than 10% of that.

... Phil

We have been using shunts for AC and DC calibration for a long time, and =

have had good results. I know that they do have some limitations, but = they=20 work well for the type of equipment we calibrate. One important feature = is=20 that a 2500 amp 50 mV shunt, as we normally use for high current test = sets,=20 will handle surge currents up to 30,000 amps, whereas the LEM = transducers do=20 not have that wide dynamic range. For my own purposes of calibrating=20 Ortmasters, I can only supply up to 500 amps with an easily handled = portable=20 source, so perhaps an LEM transducer would be useful.

I found an LEM LT1005-T on eBay for $150:

And the specs:

It appears to be about 0.4% accurate, but I'm not sure how that = translates=20 to a 50 amp current. The transfer ratio is 5000:1, so 50 amps will = provide=20

10 mA. The offset is typically about 0.4 mA, so that is 4%. Seems like = it=20 won't really fit the bill.

Perhaps the Danfysik 1000A model might be better with 50 ppm offset,=20 although at $1500 I think I'll stay with what I have. But thanks for = the=20 suggestion.

Paul=20