The B+K Precision Model 2833 4½ digit True RMS multimeter

My B+K Precision Model 2833 Digital Multimeter on top of my VuData scope and next to my Heathkit V7A VTVM
BK Precision Model 2833

I got this specimen from a hamfest for the heck of it, as this is my first 4½ digit (19999 count) multimeter as well as my first true RMS meter. Unfortunately my multimeter collection keeps unnecessarily growing... This looks like an early 80s LCD model which has many resemblances to my Viz meter.

This meter supports DC/AC, has a (SLOW) continuity beeper, and dB mode. The usual volts/amps/ohms/Hz are there too.
Power Source6 x C-sized Alkaline, approx 1000 hours. External 7.5VDC 100mA, barrel positive
TypeIntegrating, Intersil ICL7129
Input Impedence11MΩ in 20V range
Display4½ digit LCD multiplexed
approx 2 readings per second
AC/DC V ranges200.00mV 2.0000V 20.000V 200.00V 1000.0V
AC/DC A ranges200.00µA 2.0000mA 20.000mA 200.00mA 2000.0mA and 20.000A
Resistance200.00Ω 2.0000KΩ(D) 20.000KΩ 200.00KΩ(D) 2000.0KΩ 20.000MΩ(D)
Continuity mode with beeper that can be disabled(!)
- (D) indicates Diode modes
Frequency20.000KHz 200.00KHz
dBDecibels using true RMS
A button is also available to hold the changing meter.


This device uses 6 UM2 "C" sized batteries. I measured the current to be around 5-6mA. A full capacity C cell holds 8Ah (Alkaline), 3.8Ah (C-Zn), or 5Ah (NiMH), meaning this should last around 1300 hours on a set of alkaline batteries, which is kind of pitiful as a set of 6 C cells isn't cheap. The C-Zn will last even fewer at around 600 hours, but typical ICL7106 meters will do 200 hours on a single PP3 (and you can get two per pack) but you need to buy at least two packs of C cells off the bat to fill this meter. A 7.5V coaxial DC power input is on the back to power externally. It appears the DC input will cut off the battery and will not charge like the Viz.

First impressions of my BKP Model 2833

Well, the continuity check was a disappointment as well as battery consumption. Also the Hold button will "hold" the screen when you first power on, making it look like things aren't working. There are four shrouded banana jacks that accept inputs. The 20A and 2A banana jacks are white in color, which at least is some visual indication they're different than the usual red/black.

I got the device with a pair of Fluke test probes, which seem pretty good, and one reason I sprung for the cash. Alas the batteries was a bit of an letdown but I knew about that ahead of time, hoping I can use the external power jack. Even if I get 6 "heavy duty" C cells from Dollar Tree, it will cost $2 for a set. $2 will get four PP3 for my Fluke which will last it 4000-8000 hours! Even my Tenma and other "200" hour meters, they will get 800 hours ($2 buys 4 Mn-Zn batteries) which still exceeds the 600 hours. I suppose that's what you get for old ICL7129 meters...

External AC power

Well, what if I don't want to use batteries? So time to take advantage of the power port, that none of my other meters have (except for the Viz that can take 120VAC directly). So, I found an LG 5.1V 700mA switching power brick from a phone which is gone. I picked this one as it could be opened without destroying the case, and also it was a class IV. I cut off the old connector which probably was for some phone and attached a 5.5x2.5 coaxial, positive barrel, negative tip as it says on the back of the unit.

However the voltage is a bit too low, 5.1 volts is well below the voltage needed to power the ICL7129 - 7.5 volts is needed. So I hacked it to 8.5V by opening the power brick (which is conveniently openable by removing two screws) and swapping R11, the 12KΩ surface mount resistor (marked "123") to 22KΩ (marked "223"). In the following photo, R11 is the surface mount resistor to the upper left of the "R11" text, which is just to the upper left of the circuit board notch along the bottom of the board. Yes I had to use batteries to test this hack (used the meter to test its own future PSU though I could have used one of my others in the "collection"), so far so good.
LG 5.1V switching wall wart reverse side
Note that the 7.5V that it says on the back is for an unregulated supply, which tends to peak above 9V. The PSU must be around but must not exceed that of a typical set of alkaline cells, especially when new. Since a new C cell can be up to 1.55-1.6 volts, the PSU must never exceed 9.6V. However on the low end 7.5V is 1.25V/cell, which BKP probably chose to match that of NiCd cells. Alkaline cells can be lower, probably 1.1V/cell before they're dead, so likely something less than 7V will trigger the low battery indicator and then stop working. I'll need to test this at some point.

I guesstimated that I needed a 20KΩ resistor but couldn't find one, but 22KΩ I did have. 8.5V is well within the voltage of the power pack and thus it was chosen. I should also replace the two 220µF caps on the output which are rated for 10V but didn't for the time being... And of course the 700mA is well overkill for the typically less than 10mA the meter uses. Perhaps I should add some LEDs to backlight the LCD...

Now I can leave this multimeter on anytime just like the Viz. Not only that, my Kill-A-Watt doesn't even detect the power consumption of the meter at all, it remains at 0.0 watts.


I measured my 12V SLA battery to see how badly calibrated it is:
BK Precision 283312.584Stable
Fluke 7712.57Stable
Tek DM50212.5812.57 cold, flickers between 12.58 and 12.59 after warming up
CenTech P9867412.63Stable
I guess I can say that this meter should be about right though like the Fluke and Tek they've not been calibrated for a long time, and the Mastech/CenTech is way off.