Brymen BM805 and BM807 review and teardown

This is the review of two Brymen multimeters of the BM80X series. This is the low-cost series from Brymen with a price of less than 50€ for the BM805 and 80€ for the BM807. The two meters are almost identical but the BM807 add …

TRUE-RMS, temperature measurement and the LCD backlight.

Size and shape of the multimeter resemble that of a Fluke 87, just with a little more old style design.

These models are both 4000 counts autorange multimeter and have the following functions:

  • voltage, ohm, capacitance, frequency, current measurements
  • continuity test
  • diode test
  • relative mode
  • display hold and max hold
  • auto power off
  • temperature measurements (only BM807)

Both models are UL LISTED and made in accordance with the following specifications: EN61010-1 CAT II 1KV DC/AV – CAT III 600V – EN55022/A1 CLASS B – EN50082/1, IEC801-2/3

The package includes a pair of test leads, two AAA batteries and a K-TYPE temperature probe (only BM807).

The display of the multimeter is big and very clear but like other Brymen multimeters it seems to lose some contrast when watched from above.

Range switch is soft and precise and almost any function of the multimeter has it own position.

The holster is made of soft plastic and seems quite reasonable quality for the meter price, anyway it’s not the same quality of the top range multimeters.

Test leads included with the meter have a good rating at 1kV CAT IV 10A. The cable is made by PVC and they have a insulated head that expose only few millimetres of the tip. They may be good for hi-energy measurements but they are not the best for electronic because insulation cannot be removed.

In the back of the meter we find the tilt bail, even if a little flimsy, it permits to keep it in vertical position and exercise the range switch and buttons with one hand.

The buttons under the LCD are soft and don’t miss a shot. On the lower part of the meter, we have the usual 4 banana jack: one common, two for the current measurements and the last for all the other functions.

The BM807 offer also some sort of emergency LCD back-light, unfortunately like other older Brymen multimeters the implementation is quite horrible.

Apart from TRUE-RMS measurement BM807 offer also temperature measurements by using a K-TYPE probe with one grade precision. Included K-TYPE probe is the same probe included in all Brymen multimeters and can be used up to 250° C.

Accuracy verification

I have some precision instruments like a DC calibrator, DC current source, and some Vishay precision resistor that can verify the calibration of these multimeters at some ranges. These instruments where cross checked with a Keithely 2001 7+1/2 digits multimeter during the “calibration” checks.

In the first check I applied a voltage of 10,000V, 3.000V and 300,0mV and both meters where just few counts out. In the DCV measurements the specification declare a typical accuracy of 0,5% +3d (4V~400V).

A function generator and the Keithley 2001 where used to “calibrate” also the ACV range of the BM807. The BM807 with TRUE-RMS reading was able to read the correct voltage of a triangular waveform up to 1,5KHz (declared bandwidth of 1kHz). Bandwidth and crest factors of this multimeter is not the best, but I think anyway it should be enough in many situations.

Frequency test was accurate up to 14MHz. This meter has not duty cycle measurements.

Capacitance test is specified up to 3000uF. Measuring this big caps is accurate but very slow (more than 20s in the 1000uF test). The lower limit is set at 50nF but there are no specification in this range. This does not stopped me to test the meter with a very small cap like 0,47nF. Many multimeters succeeded to measure this small cap so I decided to give it a try. Booth meters, despite having activated the relative mode to delta out the internal capacitance of the leads, measured almost double capacitance.

Continuity test is very fast but not like a Fluke. Diode test has an open circuit voltage of 1,6V so it’s just for testing diodes, transistors and IR leds.

Current measurements have three ranges: 0~400uA, 0~400ma, 0~10A. The meter uses reasonable shunts resistors like 100 Ohm, 1 Ohm, 0,01 Ohm so it will not have too much burden voltage when measuring low currents. The meter has also the beek-jack function that ring like a crazy if you turn the range switch out of the current measurement when the leads are attached to the current jacks. This will minimize the possibility that you will try to measure voltage (or Ohm, etc.) when the meter has leads in the current jacks.

Battery consumption is typically less than 3mA, only during continuity test it raise up to 4ma. Power drain when the meter is in auto power off state is 285uA. The battery warning appears at 2,3V and up to this point all the three fundamental measurements (DCV, ACV, Ohm) present a stable reading. I noticed only few count drop on the ACV measurements on the BM807. At 1,7V the display begin to dimm and the meter shut off.

I notice one of the meters (BM805) was few counts more accurate than the other. By checking the serial number I think the BM807 is one year older than the BM805. This will probably means that the meter has drifted just few counts in one year span.

A look inside

Opening the meter reveal a simple and clean construction. Input protection as any Brymen multimeter uses PTC, resistors and spark gap so it should well survive any transient or error of the user. I can see also many insulation slot on the hot input side. Current measurement circuit is protected by two HBC fuses rated at 500V (200kA for u/mA range and 20kA for the A range) that should be enough safe.

On the BM805 there are some unpopulated IC footprints that on BM807 are used by the TRUE-RMS converter (AD737J) and by the op-amp that is probably used for measuring the temperature plus a third IC that probably is used in conjunction with the TRUE-RMS converter.

The ADC is a COB and is covered by some epoxy or resin so no identification is possible.

On the PCB you can find also some trim-pot and a bunch of passive components. PCB has a clean design and soldering job is very good.

Mechanical

The meter case is made of three parts, top cover, bottom cover and a big soft plastic o-ring. Top and bottom cover embrace the o-ring in a quite original way that I’m not able to describe here. The result seems very effective and the meter feels very solid at hands. I think this construction is mostly for blast protection because there is no o-ring in the battery cover or other parts of the case.

The hostler is pretuding the front of the meter so it can offer some protection to display and range switch in case of a fall.

Generally speaking all construction seems quite good and more than adequate to the price range of the meter.

Conclusions

With a price of less than 50€ and not so many functions, BM805 is clearly made for starters that like to have a good multimeter with a low budget.

The BM807 with its price of 80€ seems to point to a more advanced user and have any function a complete instrument must have.

I think both meters can play very well in their respective price league. Like any Brymen multimeter I had tested they are build with good quality specifications and you can easily bet that these meters this will last more than any other sub 50€ cheap Chinese multimeter.

I think the new BM25X series is a better option for the price, but if you are on a low low budget, and want to save more this can represent a good choose.

If you liked this multimeter and want to buy one it is available in my shop →here or if you feel more comfortable you can buy it also form my store at eBay.

Thanks for reading this post up to here and if you liked it please share with your fiends, comment it and let me know what you think. CIAO – Domenico

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Fig. 1:
on the tilt bail

Fig. 2:
back and holster

Fig. 3:
BM807 backlight

Fig. 4:
teardown (on left BM805)

Fig. 5:
test leads

Fig. 6:
K-Type probe

Fig. 7:
battery compartment

Fig. 8:
teardown (on left BM805)

Fig. 9:
PCB datail BM807

Fig. 10:
PCB datail BM807

Fig. 11:
PCB back side

Fig. 12:
case datail

Fig. 13:
o-ring datail

Fig. 14: 3,0000V DC
accuracy test

Fig. 15: 10,000V DC
accuracy test

Fig. 16: 300,0mV DC
accuracy test

Fig. 17: 4,00V AC 1kHz
sinusoidal accuracy test

Fig. 18: 4,00V AC 1kHz
triangular accuracy test

Fig. 19: frequency
counter 13Mhz

Fig. 20: 3,1180 Ohm
0,01% accuracy test

Fig. 21: 3,1180 Ohm
0,01% accuracy test

Fig. 22: 10,00k Ohm
0,01% accuracy test

Fig. 23: 10,00k Ohm
0,01% accuracy test

Fig. 24: 100,0k Ohm
0,01% accuracy test

Fig. 25: 100,0k Ohm 0,01%
accuracy test

Fig. 26: 50,0mA
accuracy test

Fig. 27: 50,0mA
accuracy test

Fig. 28: 3,000mA
accuracy test

Fig. 29: 3,000mA
accuracy test

Fig. 30: 250,0mA
accuracy test

Fig. 31: 250,0mA
accuracy test

Fig. 32: 1000uF
capacity measurement

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