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Old 9th November 2012, 08:10 AM   #1
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Default Bench Multimeter - Which one to get ? Fluke Agilent ?

I am looking for a good used on a budget bench multimeter.

I have been looking at the Fluke 45.
I already have a Fluke 87.

Please make suggestions on which one to get and approximate price.
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Old 9th November 2012, 09:05 AM   #2
KSTR is offline KSTR  Germany
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Fluke 45 is excellent. Dual metering and useful functions for audio stuff. Good accuracy especially when you get a recently calibrated one. It's my everday meter and a joy to use.
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Old 9th November 2012, 09:10 AM   #3
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The Fluke 45 has dB measurement and "power" (watt) measurement for 2, 4, 8, 16 ohm.

Would it be good for measuring the output power of Tube amplifiers ?

As for the dB measurements, that seems like a good tool for measuring the roll off frequency and also for active crossover measurement.
What do you guys think about this ?
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Old 9th November 2012, 02:42 PM   #4
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I recently picked up a very used Fluke 8840A/AA. Nice meter, but now I see the Fluke 45 looks even better for the typical hobbyist.

It does look like the 45 lacks 4-wire resistance measurement capability.
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Old 9th November 2012, 07:19 PM   #5
macboy is offline macboy  Canada
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I have two Keithley 199 5.5-digit meters. They are great. They have true RMS AC with wide bandwidth (I measured 800 kHz at -3dB), 4-wire Ω, dB, and +-303000 count display. They actually report 6.5 digits over the GPIB bus. Mine both have the scanner option, so I can automatically or manually switch among 8 inputs. I picked one up very cheaply on eBay; the seller couldn't get a reading and listed it as "for parts/repair". Actually it didn't take readings because the trigger wasn't configured, and I had it taking good readings within a few button presses.

I would recommend getting one with LED or VFD display, not LCD. The readability of an LCD on a bench instrument is generally very poor since overhead lighting doesn't strike the display directly so contrast suffers (not usually a problem for handhelds). I can hardly believe that HP used them for so long on so many otherwise great instruments. Shame.

4-wire Ω isn't a big deal; you can use the zero feature with a 2-wire measurement to get results that are about as good. "Compensated" 4-wire is worth having, since it compensates for thermal/Kelvin voltages in the sense leads.

Keithley should be on your short list next to Agilent/HP and Fluke.
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Old 9th November 2012, 10:31 PM   #6
KSTR is offline KSTR  Germany
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Quote:
Originally Posted by manp111 View Post
The Fluke 45 has dB measurement and "power" (watt) measurement for 2, 4, 8, 16 ohm.

Would it be good for measuring the output power of Tube amplifiers ?
Yes. You need to load the amp with a power resistor and then measure AC voltage accross it, after setting the reference value "4 Ohms" etc to the value of your load resistor plus selecting power for display.

Quote:
As for the dB measurements, that seems like a good tool for measuring the roll off frequency and also for active crossover measurement.
What do you guys think about this ?
You can get freq. response data/graphing by using a sine generator and reading frequency and AC voltage in dB's at different frequencies. Then input that into an Excel spreadsheet and plot the results. You don't need dB value for this, normal voltage reading is OK, too, Just tell Excel to plot a logarithmic Y axis.

Using a soundcard and a (freeware) measurement software is much more convenient for audio frequencies, though. Active XO's a measured in the blink of an eye.
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Old 9th November 2012, 10:39 PM   #7
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Quote:
Originally Posted by Stormrider View Post
I recently picked up a very used Fluke 8840A/AA. Nice meter, but now I see the Fluke 45 looks even better for the typical hobbyist.
It does look like the 45 lacks 4-wire resistance measurement capability.
@manp111: If you are looking for an affordable, high precision instrument: I would want to support Stormrider on that statement.

The 8840A has excellent long drift specs and very good overall accuracy. Check for the AC true RMS option - but for the GPIB option only, if you are into it.

It is hard to get a better bench-top DMM bang for the buck in my humble opinion.
I have seen some FLUKE 8840As which were sold on ePay for less than 100USD incl. shipment. Ask for a picture of the VFD front display in operation, so you are not bidding for a dim one.

Cheers,

THDplusN_bad
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Old 11th November 2012, 06:04 AM   #8
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Thank you guys for the input
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Old 11th November 2012, 06:07 AM   #9
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How do the Fluke 45 and 8840A compare to each other ?
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Old 11th November 2012, 01:32 PM   #10
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Default It all depends on your requirements ...

Hi,

the Fluke 45 is nice due to its dual display.
The 8840A is different (and older) from the 8842A, but even beats it on long-term accuracy.
Both beat the Fluke 45 on accuracy, i.e. by a factor of 3 or more on DC voltage accuracy.

For typical repair and maintenance work on tube amplifiers, the accuracy of all three models would be more than sufficient I'd say.
Others might say they are all overkill anyway.

A true advantage of FLUKE products is that you can download service manuals for most equipment from their website. Which is worth more to me than a fancy display or a brochure printed on glossy paper.

What is better for you depends on your personal preferences and what your requirements are.
I would study the technical specs which are all available on fluke.com and then decide...

Cheers,

THDplusN_bad
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