[volt-nuts] Fluke 845AB Null Detector

Alan Scrimgeour scrimgap at blueyonder.co.uk
Fri Mar 19 20:04:16 UTC 2010

Oops! Forgot to check the manual.
Your memory is correct.
Mine meets the noise spec. but the zero control covers too large a range and 
consequently it's impossible to turn it in small enough increments to zero 
This is what the 845AB manual says about noise (and zero):
MAXIMUM NOISE (input shorted)
RANGE                    NOISE (peak-to-peak)
1 µV                          0.20 µV
3 µV                          0.25 µV
10 uV - 1000 V      0.30 µV

Better than 0.15 µV/hour
Better than 0.3 µV/day

Less than 0.1 µV/°C from 15° C to 35°C
Less than 0.2 µV/°C from 0° C to 50°C

±5 µV minimum


----- Original Message ----- 
From: "Mark Sims" <holrum at hotmail.com>
To: <volt-nuts at febo.com>
Sent: Friday, March 19, 2010 6:35 PM
Subject: [volt-nuts] Fluke 883AB differential voltmeter

> The noise spec on the 845 is 0.2 uV (if I remember correctly).  Mine seems 
> to be mostly within 0.1 uV.
> As far as battery replacement,  I still used nicads (since I had them). 
> One advantage of nicads over nimh cells is they are more robust.  They 
> tolerate overcharge better and have much better "shelf life".
> On a lot of replacements I do use the low self discharge NiMH cells. 
> Their self discharge rate does seem to be greater than advertised...
> For circuits that trickle charge nicads (at say C/12),  replacement with 
> NiMH cells will give a C/36 charge rate (assuming three times the nicad 
> capacity).   This is OK,  particularly if you don't leave them on charge 
> permanently.
> Speaking of overcharging NiMH cells...  I put a dead 3200 maH 6 cell pack 
> on a constant 1.5 A charge and went to the local surplus store...  no 
> problem...  back in a couple of hours.   Got stuck in a nasty traffic jam, 
> got back in 3.5 hours.   The pack had exploded and let the magic smoke out 
> of one of the cells...  actually magic carbon dust.  Parts of the pack 
> were scattered over a 10 foot radius.  Nasty black powder everywhere... 
> parts of pack stuck to walls...  etc...
> _________________________________________________________________
> The New Busy is not the old busy. Search, chat and e-mail from your inbox.
> http://www.windowslive.com/campaign/thenewbusy?ocid=PID27925::T:WLMTAGL:ON:WL:en-US:WM_HMP:032010_3
> _______________________________________________
> volt-nuts mailing list -- volt-nuts at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there. 

More information about the volt-nuts mailing list