Clarification of the BK Precision multimeter from the $100 shootout

[doctorm]

on the tequipment website and some others linked to it, they have different values for the ranges the multimeter has.

the one that is most inconsitent is the capactence range. eaither they say the top value goes up to 66uf or 66mf and idk which ones it is.

can someone please confirm this? thanks.

[EEVblog]

The 2709B goes to 66mF (66,000uF)

Dave.

[McPete]

I splashed out and bought one (Well, I cheaped out on buying an 87V for now ), and one of my major justifications for choosing the BKP was that it has an great range and resolution on capacitance. Unless you're playing around with Supercaps, or those crazy 1 and 2F ones that get used to prop up subwoofers, 66mF is more than enough for most applications.

[saturation]

If you need fairly large capacitance measurement and don't do it often, all you need to do is put a resistor in series and a stop watch, and calculate its time constant.  ohms x farad = Vdc x 0.63

So if you want to measure what you think is 2200 uF use a 10k resistor for practicality:

.0022 F x 10,000 ohms = 22 seconds.  Pass say 10V to it and when it hits 6.3V you can calculate the actual capacitance from the known resistor.  If you know the output resistance of your DMM well and its voltage, you can measure capacitance directly from the DMM with just the stop watch.

seconds/ohms = capacitance in farads

Because small capacitance is harder to stop watch, you need large resistors to be practical, its better for DMM with onboard capacitance to measure the small ones, because the larger caps can easily be time constant measured. 

[McPete]

Just a question for anyone else who happens to have bought one... Does yours NOT beep at all on the Frequency range? I noticed it when I was doing the calibration verification on mine, and not a peep... Not at power on, not at a button press. Do I have a freak, or is that normal for the BK 2709B?

[AlphZeta]

doctorm,

I just bought one as well... yes, it doesn't beep in frequency mode even when changing ranges manually. Weird.

[ivan747]

If you need fairly large capacitance measurement and don't do it often, all you need to do is put a resistor in series and a stop watch, and calculate its time constant.  ohms x farad = Vdc x 0.63

So if you want to measure what you think is 2200 uF use a 10k resistor for practicality:

.0022 F x 10,000 ohms = 22 seconds.  Pass say 10V to it and when it hits 6.3V you can calculate the actual capacitance from the known resistor.  If you know the output resistance of your DMM well and its voltage, you can measure capacitance directly from the DMM with just the stop watch.

seconds/ohms = capacitance in farads

Because small capacitance is harder to stop watch, you need large resistors to be practical, its better for DMM with onboard capacitance to measure the small ones, because the larger caps can easily be time constant measured. 

Yeah, it's amazing how we get convinced we need a $400 multimeter to test a 47,000uF cap once in a year. Some times you have to go back to the basics.

[saturation]

Yes.  Handheld LCR meters are not as cost effective unless you want speed.  The R in those meters are often not as good as a good DMM;  the C is about 0.5%, typically 2x more accurate than DMM which are often 1%, and the L often is not in DMM.  However if you don't do it that often, you can measure L if you have a function generator and a scope, just use the reactance formula.

Yeah, it's amazing how we get convinced we need a $400 multimeter to test a 47,000uF cap once in a year. Some times you have to go back to the basics.