EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: signals on February 17, 2015, 06:51:47 pm
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I hope I just got a deal.
I just bought a Keithley 2015 6.5 digit THD multimeter with a current NIST-traceable calibration certificate for US$450! It's a "refurbished" unit that was purchased new in 2011 by a US-based metrology lab/test equipment dealer and has been in their rental fleet since. They are even offering a 120 day warranty at that price. Came in just under $500 with tax and shipping. That seems to be a better price than anything I can find on eBay, even for an uncalibrated model of unknown vintage, especially if you factor in the shipping.
I had been looking for a bench meter, but hadn't decided which one yet. I had even considered the 34461A or the 8846A, but that would have been wasted money on a flashy display. I really only need a bench meter with RS232/USB output so I can log readings to a PC. I probably would have been fine with a 5.5 digit meter. But, I found this deal and the decision was made. Not sure how much use the THD analyzer will be to me, but I guess it's a neat party trick. (At the right sort of parties.)
Since I know this unit is only 4 years old, I'm hoping I won't have to worry about leaky caps or worn out VFD or any of the other typical problems these things have for a few years. Anything else that I should specifically check out once it gets here?
I was a little worried about it being in the rental fleet too, but I'm really wondering how much hard use it would have seen. If you were going to rent a 6-1/2 digit multimeter in this class, why wouldn't you just rent a 34401A? Or if you are a Keithley snob, the 2000? This would probably only have been rented when the THD analyzer was an important criteria, and it seems like a pretty specialized task, especially given the limitations of the THD analyzer on a 2015. So, it probably sat on a shelf for most of its life only coming out for re-calibration when it was time. Or is this wishful thinking on my part?
Won't have it in my hands until UPS Ground is finished with it, so I'll keep my fingers crossed that I get a pristine example of a 2015 with cal when it shows up.
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lots of reasons why one would want the keithly, shrouded plugs, the THD (probably the main reason), the insane update rate compared to the 34401a, the scanner card, it's what they already used and knew and temporarily needed another, it cost less to rent maybe or was the only thing their prefered rental house had in stock.
I would trust a rental a fair amount actually, because the company probably did a thorough check every time it was returned to see if they could ding the customer for any damage.
I also recently got a 2000 on ebay sort of by accident. I did a lowball $250 offer for a 2000 w/scanner supossedly in great shape and listed for $550. I'm wondering now what I'm going to find wrong with it since they were willing to let it go at that price. I figure I could resell the scanner card and recoup $150. I have an unhealthy number of 3478As to compare it against, nothing to check that last digit though.
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I have 2015 as well and as far as I know the multimeter part is the same as 2000. Why would you go for something else (Agilent) of the same age if you were renting years ago? This thing has resolution and precision. THD spec is 94dB which is just about enough for 16 bit audio and seems sufficient for verification of even audio amplifiers, which is what I use it for. While not spec'd that high, the limit of the THD display is 0.001% (100dB) and I confirmed with some ultralow distortion oscillators that its noise floor indeed seems to be right there, so while it may not be precise in those last few dB, it does look capable of showing if you're at/beyond the limits of 16 bit audio. The only thing that I find a bit limiting is that the built in signal generator THD is something like 70dB, although that is still quite a bit better than your typical function generator.
I paid $550 canadian for mine and while it was not officially calibrated, it seems bang on (using a 10V reference I bought). One thing that is nice is real time THD, you can simply increase volume on your amplifier and you can easily see where it starts clipping or running out of power and then switch to AC meter and get the voltage. Or you can do it all programatically through GPIB.
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Sure, I was having this fantasy of people looking at the rentals list and going "THD Meter? What the heck is that?" and passing it by for the 34401A, and you guys have to come burst my bubble and make me think that I'm going to get one that's all grimy and beat up from years of constant rentals. :P
While I agree that a rental might have been kept in better shape than just some lab instrument sitting on a bench or in a rack in industry somewhere, I also know how some people treat rental cars and that scares me a bit...
Thanks for the input!