General > General Technical Chat
Bench Multimeters
ngkee22:
I have been looking through Ebay on a good bench multimeter. I prefer the HP 34401A meters and there seem to be plenty of them for sale. I found a Fluke 8846A the other day, used, for $600 but got to it to late to get it. They seem like good meters so I started looking for other Fluke bench meters. I came across a Fluke 8842A bench meter on ebay that looks nice and will probably do what I want. It is only 5 1/2 digits instead of the 6 1/2 I was looking for, but I think it will work fine.
I wanted to know if anyone else has had any expereince with this model, 8842A, or any other fluke bench meter and what your thoughts were.
Also, feel free to suggest any other models that you feel are good for their value.
alm:
I have written a few posts about alternatives from Keithley and HP on this forum, should be easy to find if you use the search function. The more recent instruments like HP 34401A and Keithley 2000 tend to cost quite a lot more than the older instrument. The basic voltage/resistance measurement is usually similar, but they do offer extra features like diode test, continuity and frequency. In my opinion the Fluke 8840/8842 is usually overpriced, alternatives from HP and Keithley are often sold for about half the $200 or so that a Fluke 8840/8842 tends to fetch, and keep in mind that some essential features (AC and GPIB?) were optional on the 8840/8842. The VFD is nice as long as it's not dim from being left on 24/7 for years, but in my opinion LED displays are pretty close, I'm not a big fan of LCD for mains-powered applications though, especially without backlight. Some older full-rack instruments (eg. HP 3456A/3457A) can also be a good deal, but are a lot larger and more expensive to ship. If you want to interface these meters with a computer, you need GPIB. RS-232 came later.
slburris:
If you don't mind a boat anchor, the Fluke 8505A (a nice 6.5 digit meter) usually
sells on Ebay for < $100. I have one (and a Fluke 8502A) and love them. But
if space is at a premium, stay away.
Scott
Rhythmtech:
I would evaluate what you want from the meter before picking one out based on price. You'll find that holding out for the one that does exactly what you want will be far easier to live with in the long run. Depending on how much you can spend too, it might be wise to look into refurbished meters instead of ebay, you'll usually get a guarantee and a warranty with a refurb that you may not get with an ebay unit.
The HP 34401A is a favorite of mine it has high accuracy, PC interface usually RS-232 or GPIB, is very configurable for different averaging, capture rates, and is fairly rugged for its capabilities.
rf-loop:
I have HP3456A and 3457A. Some time ago I also have 34401A (some weeks for testing)
3457A have more functions. Good statistic and other functions, more than 3456A but 3456A have better short time stability and maybe less noise.
34401A is nearly same accuracy but surprice it is not very good. 3456A is better if look stability. Specially short time stability. 3456A is only transfer standard quality (in 2ppm class) if look these three meters.
34401A display go very easy bad (short ageing and it is bad). It is terrible look after quite short time use. Display digits/segments have very soon lot of brightness variations. (but spare part is not very expensive)
In elder equipments also inside voltage referenge have good ageing and many times they drift less. New machines need ageing becouse first 1-2khrs with new equipment have most terrible ageing drift.
3456A is very good equipment if look stability and accuracy and value for money specially if look good value for voltage measurements. (but of course before buy need littlebit look that equipment is good working kondition and nobody have "adjust and repair" it. Most of peoples do not know how to handle these equipments inside. (also if they are electronic "professionals")
If want get accurate measurements with these equipments need also know how to do accurate measurements. There are many things what need care... not only thermal emf with test leads.
Also 3457A is good but specially if use long averaging and/or slowest mode. (also it can 7 1/2 digits but not directly) It is more "noisy" than 3456A. This noise is looks random and it can clean with averaging but in this case measurements go slow.
34401A is nice small and many functions but after testing I can not see any better accuracy.. I can see only more bad accuracy.
One interesting point...
I have test my 3457A with one month old cal.certified 3458A super meter (cal specially fine adjusted and then certified). For comparing check Voltage source was Fluke DCV calibrator. I test only DCV becouse no good ACV and Current source. Most bad error was 10ppm and my 3457A have more than 10 years old calibration and all errors was so that errors are between -10ppm and +5ppm. It was very amazing. (but it was of course only in this one time and I can not know how it is if I test agen after moving and different temperature and so on). Also make some test with good and specially accurate Resistance calibration "standards". (Example: reference was labeled 100.00345 Ohm and 3457A show 100,004 Ohm. Ref module 1,00002 Ohm and HP show 0,99917 Ohm.) maybe need do calibration some day.
After this compare in home I compare my 3457A and 3456A. 3456A looks same kind of error (maybe less error) and also this cal is very old and uncnown date (but sure more than 10-15 years old cal)
This time I have not anymore this 34401A for compare. (I put this out becouse I do not trust this kind of plastic "cheap" stuffs.)
For best DCV accuracy value for money I recommend 3456A if it is in good original condition. (if someone have "repair and adjust" it... do not touch. Also this term "refurbished" is very flexible term.... many times it do not mean anything. Also I have buy from US some equipmets with "calibrated" term in ebay. may be there is some read and write problem and guy did not know what this word meaning.
Good source (ebay or other seller) can also well explain unit condition and exactly tell how it have checked. If can not... do not buy. Do not buy if seller can not make enough testings! (most time "can not know how to test" is simple lie. )
GPIB (HP-IB) -- USB module is one solution for PC use.
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