Yes, the best thing is to do a search on ebay for "6.5 digit multimeter" there are Fluke / Philips 2535 Multimeter, Keithley 196 System Digital Multimeter, 6.5 Digit DMM, etc.
You....have just made a BRILLIANT purchase! The Fluke 8840A has a great form factor...certainly better than the3457A. It is a 200 000 count! So that half digit is a 2 not a 1....great! It has a basic DC accuracy (1 year) of 0.005% + 3 counts! Let's put that in perspective...my 3457A is 0.0017 % + 6 counts (90 day)...that means I can measure a 1,5 volt reading with absolute accuracy down to 4 decimal places...so does the 8840A! Enjoy good man!
Hi Neil, thanks for the post. I don't know of any outstanding issues on these meters. I do know there is a company on eBay selling them refurbished and calibrated...not cheap...but I think well worth the investment. Cheers, Martin.
Martin, you are a bad man ;) Look what you made me do. You have just made me go and buy a Fluke 8840A now having watch this pair of video's. It's old, but still an excellent piece if kit. The 8840A was on ebay for an extremely reasonable price, so I couldn't let it go. The same seller does have a 3457A, but I just can't justify the cost at this point in time. Oh well, more toys :)
Enjoyed the intro to the 3457A. Regarding "calibration", one should ALWAYS pay the extra and get a data report with the certificate. A "PASS" does NOT mean that a 6 1/2 digit DMM will display 10V nominal as 10.00000 VDC; the reading can be way off and still PASS due to OEM performance test might have crazy wide tolerances. Also, be sure temp of cal environment is on report. With the data report, one can begin watching accuracy trends from cal to cal, and has an option to transfer the accuracy of the fresh cal to other devices, with a little math. e.g One manufacturer's 6 1/2 digit DMM might display 10VDC nominal as 10.00155 VDC and "PASS" cal "as found". Then, the owner of DMM begins aligning widgets to "10.000 VDC" with his freshly cal'd DMM, and assumes they are spot-on when, in fact, all the widgets will be off by 1.55mV. If owner of DMM has cal data, he can factor in an offset when adjusting the widgets with that DMM, and the widgets will go out the door much closer to 10 VDC.
The CALNUM count increments once for each cal point performed. A full calibration will increment the counter several times, so your 34 means there have been 34 point calibrations, not that it has been fully calibrated 34 times. Some points: -=Front Terminals=- DC volts offset DC volts gain DC volts linearity 2-wire Ohms offset 2-wire Ohms gain 4-wire Ohms offset 4-wire Ohms gain DC Current offset DC current gain AC volts offset & gain AC current Frequency -=Rear Terminals=- DC Volts offset 2-wire Ohms offset 4-wire Ohms offset DC current offset It's also possible that a cal is just a measurement and verification that the instrument is within spec with no changes to the cal constants. In that case, you get a certificate and the CALNUM integer is not changed.
Standard deviation is the square root of the variance of a set. What you described is the max absolute deviation, which is not what the meter will return. Standard deviation is a metric of how well the measurements in a set are in agreement with one another, or how spread out the distributions is from the mean. It is not, however, the distance between the mean and the largest excursion in the set.
Martin Thx for the 2 great videos on the 3457A. I'm now after one of these beasts so a qn I hope you will be kind enough to answer: Are there any serial# to avoid? eg in HP Bulletins 87: 3457A-5. Warranty date codes 09-2623 through 09- 2644. Notification of possible defective terminal connectors. I'd assume any errors were long fixed on m/cs in the wild but who knows. Anyhow thx for the videos and keep 'em coming - love the array of meters behind you in your latest videos, very impressive! Neil
Yes, the best thing is to do a search on ebay for "6.5 digit multimeter" there are Fluke / Philips 2535 Multimeter, Keithley 196 System Digital Multimeter, 6.5 Digit DMM, etc.
The System Multimeters are great. I used to have one. But now I use my 3456A, which again is old, but really works nicely.
You....have just made a BRILLIANT purchase!
The Fluke 8840A has a great form factor...certainly better than the3457A.
It is a 200 000 count! So that half digit is a 2 not a 1....great!
It has a basic DC accuracy (1 year) of 0.005% + 3 counts! Let's put that in perspective...my 3457A is 0.0017 % + 6 counts (90 day)...that means I can measure a 1,5 volt reading with absolute accuracy down to 4 decimal places...so does the 8840A!
Enjoy good man!
Yup...plan to do that when the Fluke gets here so we can have a cross comparison. Cheers.
Thanks Dacian, it's something I plan to do in the future so thanks for the info. Cheers, Martin.
Hi Neil, thanks for the post. I don't know of any outstanding issues on these meters. I do know there is a company on eBay selling them refurbished and calibrated...not cheap...but I think well worth the investment.
Cheers, Martin.
Martin, you are a bad man ;) Look what you made me do. You have just made me go and buy a Fluke 8840A now having watch this pair of video's. It's old, but still an excellent piece if kit. The 8840A was on ebay for an extremely reasonable price, so I couldn't let it go.
The same seller does have a 3457A, but I just can't justify the cost at this point in time.
Oh well, more toys :)
Enjoyed the intro to the 3457A. Regarding "calibration", one should ALWAYS pay the extra and get a data report with the certificate. A "PASS" does NOT mean that a 6 1/2 digit DMM will display 10V nominal as 10.00000 VDC; the reading can be way off and still PASS due to OEM performance test might have crazy wide tolerances. Also, be sure temp of cal environment is on report. With the data report, one can begin watching accuracy trends from cal to cal, and has an option to transfer the accuracy of the fresh cal to other devices, with a little math. e.g One manufacturer's 6 1/2 digit DMM might display 10VDC nominal as 10.00155 VDC and "PASS" cal "as found". Then, the owner of DMM begins aligning widgets to "10.000 VDC" with his freshly cal'd DMM, and assumes they are spot-on when, in fact, all the widgets will be off by 1.55mV. If owner of DMM has cal data, he can factor in an offset when adjusting the widgets with that DMM, and the widgets will go out the door much closer to 10 VDC.
Excellent, a great meter.
The CALNUM count increments once for each cal point performed. A full calibration will increment the counter several times, so your 34 means there have been 34 point calibrations, not that it has been fully calibrated 34 times. Some points:
-=Front Terminals=-
DC volts offset
DC volts gain
DC volts linearity
2-wire Ohms offset
2-wire Ohms gain
4-wire Ohms offset
4-wire Ohms gain
DC Current offset
DC current gain
AC volts offset & gain
AC current
Frequency
-=Rear Terminals=-
DC Volts offset
2-wire Ohms offset
4-wire Ohms offset
DC current offset
It's also possible that a cal is just a measurement and verification that the instrument is within spec with no changes to the cal constants. In that case, you get a certificate and the CALNUM integer is not changed.
Standard deviation is the square root of the variance of a set. What you described is the max absolute deviation, which is not what the meter will return. Standard deviation is a metric of how well the measurements in a set are in agreement with one another, or how spread out the distributions is from the mean. It is not, however, the distance between the mean and the largest excursion in the set.
The standard deviation does not change with sample size. The number of digits that you can rely on does increase, though.
Martin Thx for the 2 great videos on the 3457A. I'm now after one of these beasts so a qn I hope you will be kind enough to answer: Are there any serial# to avoid? eg in HP Bulletins 87:
3457A-5. Warranty date codes 09-2623 through 09- 2644. Notification of possible defective terminal connectors.
I'd assume any errors were long fixed on m/cs in the wild but who knows.
Anyhow thx for the videos and keep 'em coming - love the array of meters behind you in your latest videos, very impressive!
Neil