Metrawatt Mavowatt 45 repair+review - Page 1
Forum section: electronics / testgear

author: TizianoHV
author_rank: Regular Contributor
timestamp: February 27, 2023, 11:06:11 pm
content: INTRO:A three-phase power quality analyzer. Since I couldn’t find anything about this meter, here my experience:2022 - After some search I found this meter on Ebay, for parts. Since I needed a digital wattmeter, and the price was affordable (60€), I decided to go for it.REPAIR:When arrived it would boot only after power cycling multiple times, but no readings were showed.After tearing it apart I found the backup battery dead, but this should be needed only to keep in memory the settings and to run the RTC.After some visual inspection I noticed that the main cap present on the power supply had a broken solder joint! Flushing the broken solder joints and replacing the dead battery with a “temporary” CR2025 (already used) brought it back to life!...One year has passed and the meter started losing his settings, time for a “definitive” battery change and to take some photos for a review. The original battery (SL-389) looked expensive so I opted for a cheaper SL-750 (3.6V 1.1Ah 85°C not rechargeable).TEARDOWNThe BOM is way over the 60€ I paid for it. The power supply consists in a step-down insulation transformer, bridge rectifier, 5V regulator, some caps and fuses. It outputs 5V regulated, 13V non regulated and 18Vac. DC voltage are used by the front panel (all digital). 18VAC to feed three small insulation transformers (5.5kV) that supply power to the analog section and ensure the necessary phase-phase insulation (one board per phase).The three small insulation transformers are kept in position by screws and nuts (no washer). All of them were loose, one of the nuts was lying around. Not nice for an instrument intended to operate in high energy circuits.Each channel (phase) uses a 16bit 50kHz stereo ADC.Curios how they built themselves the optocouplers (looks like), some pcb cutouts would have been nice since there was some dirt under the pcbs.No shielding but that didn’t give me problems, even in noisy environments (manual specify it shouldn’t operate in proximity to high electric fields).REVIEW:After all those years is still well within specs, luckily since there’s no calibration procedure.All three channels are totally insulated, channel 1 will set the measurement period/frequency and all six measurement values are integrated simultaneously. That’s convenient to measure transformers ratio, efficiency and power supply’s efficiency (you can measure AC with one channel and DC with another) and much more.The interface is not that intuitive, after getting used to it the configuration process remains slow (usually not irritating). There are some traps/bugs, while doing important measurement is better to don't touch anything. Once I was measuring the energy consumption of a device, switching from the energy display to the FFT caused a massive error in the energy counter (it went from tens of Wh to hundreds of MWh!). That’s easily avoidable thanks to 4 custom selections where you can choose all the values you need. These values are saved in the buffer (small) and can be recalled in a live graph/list.FFT, under/over voltage and spike analyzer are optional, and I haven’t used them yet.With the printer you can print readings and plots at regular intervals, pretty cool (and noisy). There’s also a serial port permitting remote operation, unluckily my RS232-usb converter is too wide to fit.And much more...There's the possibility to use a PCMCIA card to increase memory, from the manual:"The measuring results for analysis functions can be stored to non-volatile memory with the plug-in memory card (accessory PC Card). A PCMCIA flash memory card is used (type I, 5 volt, AMD, series C, 1 to 10 MByte) ..... The ATA formatting standard which is frequently used with these memory cards does not apply in this case. This results in the following restrictions:-Only memory cards of the above mentioned type from AMD (Advanced Micro Devices) with a capacity of 1 to 10 MB may be used, or other 100% compatible types.-The read-out of recorded measurement data to a PC is only possible via the RS232 interface at the MAVOWATT 45 (with interconnected modem if required). Direct read-out of the memory card to a PCMCIA slot at the computer is not possible.-The memory card can only be cleared in its entirety: The deletion of individual recordings is not possible."Is there a PCMCIA to microSD adapter? or someone know how to get such card (in Europe...)? Thanks!That's my first review/big article so be kind, if you find errors let me know

author: TizianoHV
author_rank: Regular Contributor
timestamp: February 27, 2023, 11:10:09 pm
content: More photos...

author: TizianoHV
author_rank: Regular Contributor
timestamp: February 27, 2023, 11:11:05 pm
content: ''