One of the best compact multimeters you’ll find, the Brymen BM257 – rebranded as the Greenlee DM-510A in the US – is a solid and practical test device. Part of Brymen’s 250 True RMS series, it boasts many functions and good accuracy and suits electricians in industry as well as amateurs looking for something more reliable.
Chief among the BM257’s main attributes are its typically high level of input protection and UL certification, plus it boasts non-contact voltage detection, an AutoV mode and data recording capabilities.
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Key Features
- True RMS for AC accuracy
- AC/DC voltage to 1000V, current to 8A
- Micro-amps range
- 0.2% DC accuracy
- Large backlit display with bar graph
- Measures capacitance and frequency
- Temperature input
- AutoCheck (with low impedance) to pick up voltage, continuity or resistance
- Voltage sensor, detects live wires
- Automatic and manual range selection
- Peak hold and Max/Min modes
- PC interface capable
- Lifetime Limited Warranty
- Dimensions: 6.3″ (161mm) x 3.15″ (80mm) x 1.97″ (50mm)
- Weight: 0.75lbs (340g)
Comes With
- Meter, holster and batteries (x2 AAA)
- Test leads
- Type-K thermocouple
- User manual (brymen bm257 manual)
Optional: RS232 interface for PC logging
In-depth Review of the Brymen BM257
Brymen is renowned for its functional designs and solid meters and the 257 is ergonomic and easy on the eye. While it packs a punch with its raft of features and safety rating, it is easy to operate with one hand and boasts a super-fast display that is backlit and refreshes at a high rate.
Specifications are typically very good and, as it is a True RMS device, you will get accurate readings even when measuring AC variable frequency drives.
ACCURACY
| RANGE | ACCURACY | |
|---|---|---|
| AC voltage | 60mV / 1000V | ±(1.0%+5) @ 50-400Hz |
| DC voltage | 6V / 1000V | ±(0.2%+3) |
| DC millivolts | 60mV / 600mV | ±(0.4%+5) |
| AutoV (AC) | 1v / 1000V | ±(1.4%+5) @ 50-60Hz |
| AutoV (DC) | 1v / 1000V | ±(1.3%+3) |
| AC current | 60mA / 8A | ±(1.8%+6) @ 8A |
| AC micro-amps | 600µA / 6000µA | ±(1.0%+3) @ 50-400Hz |
| DC current | 60mA / 8A | ±(0.5%+3) @ 600mA |
| DC micro-amps | 600µA / 6000µA | ±(0.5%+3) @ 6000µA |
| Resistance | 600Ω / 60MΩ | ±(0.5%+4) @ 600Ω-600kΩ |
| Capacitance | 60nF / 3000mF | ±(1.5%+5) @ 6-600µF |
| Frequency | 10Hz-50kHz | ±(0.3%+2) |
| Temperature °F | -58°F to 1832°F | ±(0.3%+6) |
| Temperature °C | -50°C to 1000°C | ±(0.3%+6) |
| Diode test | 1V | ±(1.0%+3) |
As you can see, most ranges are wide and accurate and the Brymen BM257 has enviable specs for its size and stature. Continuity is quite fast on this unit, too, although it does not latch as well as the Flukes. The only (minor) criteria that lets it down is perhaps the rather lame voltage output of the diode tester.
Current measuring capacity is, curiously, not as high as that of the BM235, although you can measure up to 15A in 15-second bursts, while the micro-amps range allows you to test delicate electronics and flame sensors.
One of the most impressive features is AutoCheck, which tells you whether you’re measuring AC or DC voltage, or resistance. This is a low impedance input (as opposed to the meter’s standard high impedance circuitry) and it will thus pick up and drain any ghost voltages in a cable.
Voltage detection: is through a sensor for non-contact detection, or via a single probe. It will detect voltage from around 20V to 440V (@ 50-60Hz) and will beep and adjust the bar graph accordingly when voltage is picked up.
The BM257 also has a PC interface and so can send data logging data to a computer with the correct adapter.
Build Quality
Brymens (and now Greenlee multimeters) are very well built and among the best produced multimeters in Asia. Along with a strong case and internals is a nice set of leads. A red rubber holster (green in USA) protects the shell, while on the rear is an okay kickstand and a less substantial battery case lid. It is easily opened and contains the two AAA batteries and HRC fuses.
Probe leads: are high quality silicone type, meaning pliability. Probe ends are actually gold plated and quite sharp for better, more accurate measurements.
Interface
Brymen also focus on their screens, where clear digits and a fast-update time make for impressive monitoring. The display on the 257 is 6000-count (3 5⁄6-digit). Refresh rate is five time per second*, and there is also a bar graph, which itself updates at 40x per second. With this speed it is easy to monitor quick-changing signals. A bright, orange backlight remains on for 30 seconds.
* Screen update is not consistent on all ranges, including resistance and capacitance, which refreshes at around 2-3 times per second.
Functions
There are several notable functions and modes on the BM257. Chief among these are the Max/Min and the CREST (peak) hold functions. The Max/Min will retain the high and low values of a signal, while peak hold is extremely fast acting (5ms) and can capture spikes. Unfortunately, standard screen hold is manual only.
There is also a relative mode as well as a range button to change the measuring dynamic from auto to manual ranging. Another nice touch on the Brymen BM257 is its range memory function, which keeps tabs of the previous range setting where the dial position has more than one range. This is especially useful on the resistance/continuity/diode position.
In addition is Beep-Jack, which alerts if you have the leads improperly inserted. Example: red lead plugged into the amperage input with the dial selector on AC voltage. With this, the beeper will sound and ‘InErr’ will show.
Safety
The fuses on the Greenlee DM-510A are high end, high rupture capacity. While expensive, they protect the meter and user should there be a catastrophic internal failure. These are easily replaced by removing the rear battery cover.
Those versed in meter safety ratings and who have been busy reviewing might notice the fairly conservative category ratings of the BM257. A lot of meters in this class will tout a CAT-IV rating to 600V, even some of the $20 cheapos. This claim should mean the meter could handle a surge overload to 8,000 volts (8kV), which just isn’t going to happen on those meters than have non-existent input protection.
The Brymen BM257, on the other hand, has excellent input protection and a CAT-IV rating of 300V. It can thus handle surges to 6kV (at 300V ‘to ground’ energies), which is no mean feat and is tried and tested. Other category ratings are CAT-III to 600V and CAT-II to 1000V.
Pros and Cons of the BM257
The Good
Compact and strong
Great build quality
Good reputation among electricians
Good functionality and accuracy
Auto-volts and voltage detection
Gold plated, silicone test leads
Solid input protection
UL-tested
The Bad
Temperature resolution could be better
Expensive to other, non high-end 6000-count meters
Data logging not very intuitive
Diode test low output
Roundup
In the Brymen BM257 review is one of the best compact multimeters you’ll find. It has many standout functions, like voltage detection, auto-volts and peak hold, and is also very accurate. Although the Greenlee re-stamped offering is pricier than the OEM Brymen, you still get a solid device that ticks all the boxes.
Alternatives: Those looking for higher resolution and more functions might like to seek out the Brymen BM829, while the Amprobe AM-570 has similar specs, albeit is a full size meter.