New Hantek DMM HDM3055B (5.5 digit)

[diodak]

There is no information on the construction of a 5.5 digit multimeter manufactured by Hantek, model HDM3055B. Therefore, I will share what is known about and what can be assumed. The purchase of such a meter is not cheap, the meter with delivery and tax fees for Poland is about 545 USD. For the amount of 639 USD you can buy the Siglent SDM3055 model. Does the 94USD difference pay off? Let's see ...

The multimeter has 2 PCBs. The analog part is the largest and occupies the entire bottom of the housing. The display part is mounted on the front panel and connected with the analog part by a connector. An interesting solution because it requires a mechanical fit and is comfortable. On the front panel PCB, we can find, among others:

• U412 MCIMX6Y2DVM05AB microcontroller (Arm Cortex-A7 528MHz)
• U410 DDR3L SDRAM 1Gb memory designated D9SFT (Micron MT41K64M16TW-107)
• U8 2G-Bit 3.3V Nand Flash Memory (W29N02GVBIAA)
• U1 STM32F030K6T6
• U2 RTC (AnalogTek company AT8307T , equivalent to DS1307)
• U417 EEPROM (24LC64 designated 4L64I)

Unfortunately, the problem of PCB cleanliness is already visible here. U1 and the capacitors at the stabilizer were soldered again. It can happen in production but can't it be washed after this process? It looks nasty.

The housing is solid, made of thick sheet metal and properly painted. All bolt fasteners are by welding nuts. The most important part in terms of measurement accuracy looks like this:

Here is also a problem with soldering.

The PCB has a pinched screen over the analog part. It covers a large area of ​​the PCB.
And at that moment a practice that I do not understand begins. Namely, several integrated circuits have mechanically removed markings. Interestingly, later painted black ... After all, it is not a problem for electronics to find out which integrated circuit it is, or at least from which group. And so, most importantly:

• the U22 reference voltage system has no markings removed and it is ADR03A
• the ADC converter (U24) has the markings removed, in my opinion it is ADS1255
• U23 temperature tgemperature sensor is LM75
• RMS U1 converter, no markings, matches LTC1966/67/68
• a lot of analog keys from the DGxxx series
• you can see some guard rings
• U3 and U18 no markings, I don't know what it is, U18 is probably an opamp - there are a lot of passive elements (capacitors) on the bottom of the PCB, I did not take it out because there is a lot of work on it
• a fairly good ADDA fan, type AD0412LB-G70 (12V), turns on for up to 2 seconds only during boot

A multimeter with a measuring range of 100mV, 1V and 10V can have a selected input resistance of 10M or high. The thing that worries me is the lack of a precise 1776 series Caddock divider. I also can't find a divider for> 10V voltage with a resistance of 10M. I know that this divider is switched on by a relay. By the way, it's even good that there are only 3. On the bottom there is a 0R002 measuring resistor in the Kelvin circuit for the 10A range. It's such quick facts.

[diodak]

The data port is RS232 and real RS485. There is a separate converter for this, interestingly using a ready-made SATA cable and connectors ...

[Kleinstein]

The high voltage divider is indeed missing - likely one the bottum side and also including the 10 V range. The specs show a high Z mode only for 100 mV and 1 V.  So a divider like 9.9 M - 90 K and 10 K or maybe slightly different values as the ADC could likely work with a little more than +-1 V.

The low number of relays is surprinig. Normally I would expect
1 Relais to separate the AC voltage part - allways connedted may not be that nice. There could be some photo-mos hidden from below.
1 Relais to switch between the divider and the direct 100mV/1 V ranges.
1 Relais to connect the Ohms source
1 Relais for the higher amps range. The lower ranges may be with FET switching.

With the 10 M input option also for 1 V, there may be even 2 separate relais for the voltage ranges: connect the divider and separate the 1 V path.

Quite a bit of the circuit is easy to recongnize, like the protection for the Ohms and cap ranges (chains of SOT23) and the AC part.
I am missing the protection for the Ohms sense inputs. 

[diodak]

I also thought that the 10V range is only 10M and so it says in the specification .. but indeed the 10V range has a high impedance option

[diodak]

I made a measurement when the inputs are short-circuited using a self-made jumper. Auto zero off.
The second photo shows a finger touching the jumper closer to HI and LO. The thermoelectric effect is clearly visible.
Interestingly, the multimeter appends the date and time to the screenshot. However, it cannot be forced to show the time while running like this. It's a pity

[Dathlonx]

Hi, would you recommend this multimeter after some time?
Or would you suggest something else in this price range? 

[BirdManPhil]

I have this meter, it's pretty good, I've had no issues so far but I haven't really tried to find problems I just use it on my bench daily. I paid $240 on ebay it was an open box demo unit and I honestly expected there to be some sort of problem at that price but it hasn't made me regret the purchase even once.

The only thing I am not a fan of is the pc software. When you are in remote mode (that's me 100% of the time) the on screen display does not adjust for the correct range so I end up making quick mental conversions all day long and thats annoying. FIX IT HANTEK!. I tried to get keysights lab software to recognize the meter, they use the same exact scpi commands and library as keysight so you would think it would just work, but nope. They software sees the meter, can send scpi commands to the meter to operate it exactly like a keysight dmm, but noooooo you can't actually connect it. Major bummer.