Part – 3
BM869 Exploring the basic featuresContinuity modeLightning fast response, clear beep sounds with no scratching, it will satisfy even the most demanding user, and my word would be that it is impressive.
The beeper stops beeping if the resistor is over the 84 Ohms.
And the maximum measured resistor in this range will be 531 Ohm before it displays OL.
(Brymen should check again the specifications on this, about the Audible threshold: between 20 Ohm and 200 Ohm range, that is on the User’s manual)
Ohms range The Agilent U1272A is the faster multimeter at the 30,000 counts that I have in my collection so far, surely the Brymen is close enough and needs a blink of the eye as delay so to perform the measurement (half second).
In the beginning I thought that it was a delay caused by the auto range, but it was not.
Accurate all the way, plus the resolution of the 50,000 counts, makes the measurement an enjoyable task.
An example about over range tolerance, in the manual range of 50K Ohm, the range will go up to 53K before it displays OL.
The smallest range is the 500 Ohm and the highest the 50M Ohm.
Relative modeWell with the BM869 I was had a major surprise in this mode.
The relative mode does not lock the auto-range.
I was able to REL-Out at zero ohms, and go up to 1M Ohm.
That is the end of the road of my DIY Resistors Decade Box of 0.1% tolerance.
Hacked Gadgets - DIY Tech Blog
http://hackedgadgets.com/2010/09/04/diy-resistors-decade-box/Impressive!
Bar graph – speed comparisonEven faster than the Agilent U1272A and the Fluke 28II, the BM869 it is adequately fast.
I tested it with my reference 10V DC source, and I repeat the test over 10 times by playing with the on-off switch of my source, the human eye is unable to catch the movement of the extending segments at this speed.
The Agilent was close enough, and the Fluke 28II looked to be very slow so to follow in this specific race.
At the Crest mode (Min-Max or Peak to Peak) the bar graph its not visible or active.
The same behavior haves also the Fluke 28II, but the Agilent U1272A it does have the bar graph active in this mode, and it is a major advantage to have a visual indication that the circuitry under test, remains active (energized).
Capacitance meter With the auto range function, the capacitor gets tested in every range (lowest to highest) for half second, and this happens again and again until the multimeter to ramp up to the correct range.
This causes a small delay nearly to one second for its one attempt.
Examples: Auto range VS Manual range.
10,000uF…7 seconds……………3 seconds
1,000uF…. 6 seconds...........3 seconds
240uF……..6 seconds...........1 second
47uF……….4 seconds...........1 second
22uF……….3 seconds..........1 second
1uF…………2 seconds..........1 second
The discharge function engages automatically and there is on-screen notification.
Notes:
The test was made with capacitors that were all ready discharged.
Test leads: crocodiles with 17 cm total cable length (UNI-T).
DC / AC volts Speaking about accuracy the BM869 side by side with the Agilent U1272A was like watching a mirror image.
The calibration on both was matching up to the last digit.
This made me to play with my DC power supply for long time, by trying to find with a major difficulty a voltage setting that the final count will be different.
About LCD speed it was a pleasure to watch them, ramp up and down as to was twin brothers.
Personally I got a bit excited due the fact that with the 50,000 counts resolution of the BM869, for a first time in my life I was able to see the output of my Professional KENWOOD PD35-10A PSU in such detail.
By using my reference adjustable DC voltage source (MICRO-CALC 1030 TimeElectronics.co.uk) I managed to get down to zero volts.
And in there the BM869 was +4 counts at the 500,000 counts resolution, at the room temperature of 16 Celsius.
On the AC modes the picture was positive too, and even I found something on the BM869 that even the U1272A does not do.
I could select interchangeable view of voltage and frequency, by selecting witch one will be displayed at the primary or secondary display.
Even at Crest mode (Peak to Peak) I got the same voltage from both multimeters up to the last count, with the help of the PHILIPS PM-5134 0.1mHz-20MHZ 20Vpp Function generator as source.
Part – 4
BM869 – Advanced featuresIntro:My fresh involvement about such product reviews caused a very positive impact even to my local Greek friends.
In order to help me out, they voluntarily offer their own test equipment as loan, so to perform in depth tests with dignity.
I like to publicly thanks Mr. Mario’s Karathanasopoulos (Version computers store) who offered to me the PHILIPS PM-5134 20MHZ 20Vpp Function generator.
Mario’s is an excellent computers engineer, with studies in England, and he is also involved with electronic repairs of laptops, computer monitors, and modern PSU.
Duty cycle The user’s manual describes as frequency range about duty cycle, the range of 5Hz – 500Hz, 2.5Vpp.
I selected the 500Hz and I connect in series the Agilent U1272A & Fluke 28II, with coaxial RG-58 high quality cables plus BNC T-type bridges, BNC to banana adapters (By Pomona), and a 50 Ohm BNC terminator.
I did take pictures of my test at 25% Duty cycle, 45% and at 88%.
There is no need to say how happy I am with the results.
Other than the prefect behavior of the BM869 speaking about accuracy, I managed to verify too that my other two industrial multimeters were spot on.
The Brymen BM869 were is par with the Fluke 28II speaking about speed, in any movement of the Duty cycle knob, the meters was ramping up instantly and this helps allot to adjust the Duty cycle by simply watching the LCD screen.
The Agilent U1272A in the Data cycle mode, was have also active and the secondary display measuring volts , and with the dual display active it was a bit slow to follow the fast ramp up, I have had to stop moving the knob so the U1272A to measure and display the Data cycle.
The poor behavior of the Agilent multimeter it did disappointed me, and at the same time it trigger me to the point to add in my criteria about future reviews, three more parameters.
a) Good enough to adjust Duty cycle.
b) Good enough to verify the Duty cycle.
c) Good enough in both.
And so the BM869 it is: Good enough in both.
Frequency counterOn the Duty cycle test, I followed to the letter all the suggested technical specifications, but for the frequency counter test, I decided to act wild.
The 1mHz-20MHZ function generator was all that I needed for a true crash test.
My goal was to discover the max stable displaying frequency by the use of square & sine wave.
At the frequency range of 50Hz – 20 kHz or even 50 kHz, all multimeters was spot on, up to the last count.
Now it was time to explore the unspecified territory, the results are very interesting, and as assistance and confirmation about the displayed frequency I did use my trusty LEADER LDC-831 dedicated frequency counter 5Hz-150MHz.
Results with square wave, and max obtained stable frequency reading:
Fluke 28II……….. 167 kHz
Agilent U1272A….285 kHz
Brymen BM869…..1460 kHz
Results with sine wave, and max obtained stable frequency reading:
Fluke 28II……….. 800 kHz
Agilent U1272A….1600 kHz or (1.6 MHz)
Brymen BM869…..7380 kHz or (7.38 MHz)
Impressive!
Unexpected results the least that I can say.
But this is the fun about crash tests, you get the unexpected.
The duration of my tests at those frequencies was limited to 10 to 20 seconds of time.
I do not suggest to any one to feed those multimeters with so high frequency, but still it is good to know of what they can do.
The BM869 specification by the book it is up to 1MHz.
Low Pass Filter – VFD Voltage Filter
Intro:By having the function generator at hand I managed to perform one relatively interesting test, the purpose of the specific filter are to eliminate high frequencies, above the 1 KHz mark, but does it? And how well it does that?
The experiment that follows are 100% my own idea.
I am not aware if it stands as realistic in the world of metrology, but it is my personal best shot, as a simple Industrial electrician.
Process: I set in series the three multimeters (BNC connectors and RG-58 cables), set the frequency generator to shine wave 50Hz and set the voltage at the max 7V AC.
The second step was to verify that those 7V AC was there with out voltage droop from 50HZ up to 20 kHz at the standard AC mode in all three multimeters.
The third step was to activate the Low Pass Filter on the U1272A and 28II multimeters, and to use the VFD AC range (Low Pass Filter) on the BM869.
Then I started to ramp up the frequency and to monitor the 7V voltage, and to keep notes of what happened all the way up to 15.5 kHz.
My first observation was that in all three meters the voltage starts to be affected at the 285 - 300Hz and upper.
And so this is the first note that worth’s to be noted, which is that the 300Hz looks to be the low end from the Low Pass filter.
The idea behind this experiment is to force the Low Pass filter to eliminate all those 7V, because it would see it as interference, or in a simplified description, as the enemy that this filter is designed to eliminate.
Now let’s see how the Low Pass filter reacts in those multimeters versus the frequency change.
Frequency…. U1272A ………28II ………BM869
50Hz …………. 7.00V………….7.00V……7.00V
500Hz…………..6.80…………..6.70……..6.80
800Hz…………..6.34…………..5.18………4.30
1000Hz…………5.86………….. 3.53……..2.42
1200Hz…………5.28…………….2.52…….1.38
1400Hz…………4.62…………….1.45…….0.83
1600Hz…………3.69…………….0.98…….0.53
2000Hz…………2.65…………….0.48…….0.24
3000Hz………….1.00
4000Hz………….0.50
5500Hz………….0.24
15500Hz………..0.00
What those numbers prove?
Well it is obvious that the BM869 haves the most aggressive filters, with the Fluke 28II as second best.
And in the case that you do have real interference and spikes, what you need most, is an umbrella against the unwanted frequencies, and it turns out that the BRYMEN BM869 it is from the best ones out there!
The U1272A looks to have the less aggressive filter, and rightfully it takes the third place in the specific test.
Temperature – Dual K-Probes The BM869 is capable to display both readings of T1 & T2 simultaneously or a single selection of the T1 or T2, or even as T1-T2 (difference of the two).
What worth’s be noted is the blazing speed at detecting the temperature.
Even in dual display mode it is just a bit behind than the Agilent and Fluke, but the time delay is not measurable because it is at the range of micro Seconds.
The Min/Max/Average (REC-R) function works nicely, in the single selection of K-Probes like T1 or T2 and records the selected one, but when the BM869 is at T1 & T2 dual display mode, the Min-Max defaults to record the T1 probe.