DMM Brymen BM235

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Brymen is one of the good DMM manufactures and have a large selection of DMM's in their program. This meter is a mid-range meter.

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The meter arrived in a red box with a feature list for their BM23x series of meters (BM235 is the best of them).

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The probes are rated for 1000V and 10A in CATIV environment, this is a very good rating and way better than the meter.

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The removable tip cover must be on for best safety.

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The plug is fully shrouded and full size.

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The thermocoupler has a single connector to the multimeter, that is considerable better than the two loose banana plugs and the general construction looks nice.

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The tilting bale is just about stable enough to change range and use switches with one hand. The switch is a bit on the hard side.

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Before it is possible to open the battery cover the sleeve must be removed.

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Both the 400mA and the 10A fuse is accessible from the battery compartment.

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Display

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The above picture shows all the segments on the display, not all are used by the meter.

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Typical display during usage, it will show the number and what measurement is selected.

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The Low-Z range will automatic detect AC/DC and do not show any voltage before it can decide that.

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The electric field detection (NCV) shows from 1 to 5 bar depending on field strength. There are two ranges EF-L(ow) and EF-H(igh).



Functions

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This meter will remember what was selected with SELECT and start in the same function next time, power off will not reset this.

Buttons: Rotary switch:
Input

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Measurements
1uF

A look at the capacity measurement waveform, it is non-polarized.

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Tear down

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I had to remove 3 screws to open it.

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Notice the two springs on the battery holder. There is also some plastic that goes between ground terminal and mAuA terminal.

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There is a lot of slits in the input circuit board.

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Input board has both wired (for 10A and mAuA) and connectors to the main circuit board.

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I had to remove one screw and desoldering two wires before I could remove the input board.

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Main circuit board is shaped like the meter and is mounted with a lot of small screws (6).

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Display uses a black zebra stipe for connection and two springs for backlight.

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One this side of the circuit board is all the switches and a resistor for the mA range. The other part is probably an inductor for the boost converter that supplies the backlight. There is also a 3 pin chip (U2: marked R11), I wonder if it is a reference. There is two EEPROM memories (U4 & U5: Marked L02, 6246W) for calibration and remembering last settings.
It looks like many of the transistors are used for protection, but there is also the backlight boost converter (Q13).
The antenna for the NCV is near J1 and is on both sides of the circuit board.

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Most of the meter is on this side of the circuit board. There is a DMM chip (U1: marked BTC J200, LP6A-0000, R780H.F) and a LCD driver chip (U3: HY2613C). The long black square resistor is the main input divider (10Mohm).
The 5 large diodes (D8, D9, D10, D11, D12) is protection for the mAuA shunt resistors. The uA shunt (R33: 100ohm) is placed close to the holes for the input terminals.

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The input board contains the four input connectors and some protection.
The two pink resistors (R30 & R38: 5Mohm) is for sensing if something is plugged in, they are also large enough that 1000V with a blow fuse will not do any damage. The resistors (R7 & R8: 1Kohm) are series resistors for the two PTC (PTC1 & PTC2), followed by 3 MOV's (SPG1, SPG2,SPG3). All this limits the voltage and current that gets to the main board.

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Conclusion

This is a fully featured DMM with a few extra functions like NCV, average, VFD and Low-Z, but it is missing duty cycle. The idea about remembering the last selections is both good and bad, it means the DMM mostly will be in the desired function, but it also means I have to check the display for function each time.
As usual the burden voltage is bad in the high mA range. The UL listing probably means the CAT ratings are correct according to US standards.
It has one problem and that is the behavior when the battery is nearly empty, a good DMM must never show wrong value!

I will call this a good DMM to use for both hobby and professional usage.


Notes

This meter is frequently sold in more or less rebranded versions.
The EEVBlog sells this meter with a blue sleeve.

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