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I found the following note with a set of test leads we use for our Agilent 34461A[1][2]:

This Test Lead Set is designed for use with the Agilent 34xxxA Multimeters, and also the U274A, U3401A, and U3402A Multimeters. Do not use with the Agilent 3458A.

I suppose they're simply not calibrated for use with other meters and 'too inferior' for use with the 3458A[3]. But afar from precision, is there any reason not to use them on a different multimeter, provided they fit?

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    \$\begingroup\$ Please add links so everyone who don't know exactly what the 34461A model is doesn't have to do the job.. \$\endgroup\$ – pipe Apr 10 '17 at 13:38
  • \$\begingroup\$ @pipe Sure, on it. \$\endgroup\$ – Mast Apr 10 '17 at 13:40
  • \$\begingroup\$ @pipe Links to the original Agilent documentation appear to be down, so third-party links will have to do. \$\endgroup\$ – Mast Apr 10 '17 at 13:44
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    \$\begingroup\$ In general, it is very poor documentation practice to say "Don't" without saying exactly "Why Not". You should not have had to ask here. \$\endgroup\$ – mickeyf Apr 10 '17 at 19:34
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The 3458A is 8 1/2 digit, calibration/metrology grade instrument. When measuring 1V, your least significant digits will be nanovolts. At this level of accuracy, you need to pay attention to triboelectric effects, thermal EMF and so on. This requires another class of testleads, usually using tellurium-copper alloys (for the EMF), teflon insulation, shielding when doing current/resistance measurements, etc - things not found in your run-off-the-mill testleads (because it's too expensive and such).

Ofcourse, if you are just doing quick and dirty measurements, you don't really need to care too much - you won't break your 8 1/2 digit meter by using normal probes.

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In addition to the excellent answer given by @JorenVaes there is also a simpler electro mechanical reason for this caution. If you take a close look at the lead connections for the 34xxxA multimeters you can see that they are made like shown here:

enter image description here

The above type of jacks are designed to be used with the shrouded type of banana plugs that look like these:

enter image description here

enter image description here

On the other hand the 3458A meter uses test lead connections that look like this:

enter image description here

As you can see the shrouded leads will not mate with the latter type of jacks. Shrouded banana plugs have come into use on many meters because of the safety they offer. The types of meters may be used in high voltage or high current applications where the user may detach the lead from the meter when it is still clipped into the test circuit.

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    \$\begingroup\$ Of course! I didn't even think of that. I'm so used to using unshrouded leads in my day-to-day life, I forgot that it's impossible to plug the shrouded safety leads into anything that's not built for them. \$\endgroup\$ – Joren Vaes Apr 10 '17 at 14:24
  • \$\begingroup\$ While the other answer is good general info, that they won't physically fit is the actual answer. \$\endgroup\$ – Passerby Apr 10 '17 at 16:45
  • \$\begingroup\$ @Passerby Not exactly. I've already mentioned the fit in my question. My Flukes will happily accept these leads for example. I was interested in both the 3458A specifically and other meters generally and got 2 answers, covering both points. So, both answers are quite valuable. \$\endgroup\$ – Mast Apr 10 '17 at 17:31

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