Fluke 1663 MFT Advice

It may be that the batteries you have droop in voltage when asked to find the quarter of an amp - the internal voltage drop of the cells that will depend on the make of battery and the quality of the chemistry within, or if they are drying up a bit during storage.

Or it may be that there is an extra resistance in the battery holder or it's wiring, which would have the same effect - are the springs still nice and shiny and holding the batteries tight ?  At the worst it may be an icky  connection internal to the device.

Test a battery on volts, to see if it is not dead, but a quick flick on the 20A DC range of the multimeter will tell you how the internal resistance is doing - though before you break your multimeter, be aware a good alkaline chemistry AA cell can blow a 5A fuse (for example if you see 10 A when shorted  and 1,5 V open circuit voltage, then that  implies about 0,15 ohm internal resistance) - and obviously such a test does drain the cells quite rapidly.

The meter hand book will tell you how the accuracy and precision vary with changing range.

Mike.

What sort of batteries? Alkaline, NiMH? New or not? Is it purely on long leads (so perhaps with higher resistance)? What are the leads' resistances and are the different sets you tried all similar?

Do you have rechargeable batteries? This is a common effect with both NiCd and Lithium cells, the internal resistance increases with age, as well as charge retention. I have several (very expensive) batteries for my TV cameras. They are great until suddenly they won't keep the full charge and won't work the camera accessories such as the on-camera light.  Investigation shows the above, low capacity and higher internal resistance. New cells (these batteries have a lot of electronics inside) and all is well. Cold weather exacerbates these effects, just like the car battery too.

Actually, real battery condition monitors - often built into fire panels, UPS and the like,  measure the voltage step as a known load is keyed on and off, rather than just the absolute  battery voltage. 

It rapidly becomes quite an involved subject, as you do not want to fail a battery in good condition, just because it happens to have been run down and is charging, or is cold, nor pass a failing battery that has a high voltage because of the temperature and the charging history. And for lead acid and Lithiums, that 'quick flick with the ammeter' that works so well on traditional primary cells is not at all the right idea - a short circuit  car battery in good shape can deliver a kA for long enough to boil the acid and split the case (as well as buggering up your meter...)

Lithium cells commonly have battery protection current limits inside and larger ones also have  fusing inside, and you do not want to operate that by mistake. (though some on Ebay really are just bare cells, caveat emptor when handling those.)

Mike

We have this with our flukes, normally a brand new set of batteries sorts it. I remember reading somewhere that once the batteries drop below 7v continuity readings don't work or are inaccurate.

If you need a primary cell that droops as little as possible under stress or when cold, things based on the lithium 1.5V cells  (example) are some of the best, far better than the  equivalent alkaline, that in turn is much better than the cheapy carbon zinc.


The price difference is marked, but then so is performance under load . (see the links for some data for the AA sizes of all 3 chemistries to compare.)

Mike.

Loose fuse holder ???