Sounds a bit weird now that I write it out. So if your high current reading is to low one option is to shave the shunt. Removing a tiny bit of material each time. How?, by scraping a razor blade along the shunt wire until the reading came up to my reference meter. So I adjusted the trim pot to improve the DC accuracy and then using my 3457A as a reference I was actually able to get the 10 amp current range within 0.25% (or better). The only range that was out far was the 10 amp current range scoring in at 3% which is just in spec based on the paperwork. The ohms ranges came in around 0.35% average and the ma ranges were again around the 0.25% average. Shockingly using my 3457A as a reference this little meter was an average of 0.25% on DC and about 0.5% average on AC. I had one goal in mind when I did so, see how accurate a $2 meter could be. I just purchased one of these from Harbor Freight for $2.00 on sale.
Not exactly what I was setting out to do. I appear to have a tendency to bring up some old posts. It is fine for small electronics circuits, provided the loose spring is not shorting anything inside. It may be a shocking or explosive experience. Also typical of cheap DMMs, although I haven't seen them that small yet 10 ohm resistor Comparing with a Fluke 179 7k5 ohm resistor Comparing with a Fluke 179 Voltage test (12V sealed battery) Ampères test (12V sealed battery with 10 ohm resistor across) Miliampères test (12V sealed battery with 7k5 ohm resistor across) In summary: do never put this DMM across the mains leads. Also typical narrow clearances, but the novelty is the slanted fuse. Typical board for cheap DMMs, with average soldering and the unfortunately way too narrow clearances. Putting the cover back without shorting everything will be interesting. The spring is not only loose from the PCB, but the aluminum stick is peeling. Several paper label warnings slapped to the back, probably to appease any lawyers. It says CAT II but does not have any indication of fused/unfused inputs.
Typical Mastech el-cheapo DMM, but with an ON/OFF switch. Sorry for the low quality of the pictures I was testing a new portable camera (also found in the same somewhere place as the DMM). Interesting: I just saw PedroDaGr8's review of another Cen-tech precious piece of equipment. Well, I decided to take some pictures that evidenced the unfortunately but expected terrible assembly and design. I just found lost somewhere a brand-new Cen-tech 90899 DMM and decided to open it up and see if anything interesting popped up.
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