Adjusting an old multimeter, Velleman DVM890
I've had this old multimeter for quite a long time (can't remember; maybe since around beginning of 2000). Nowadays I also have other multimeters that are of better quality. But I wanted to adjust it, because it isn't that accurate. I'm not talking about calibrating, because this meter is too cheaply built, so it cannot be calibrated. The meter had readings that differed noticeably in DC voltage, AC voltage, temperature and frequency in comparison with better quality meters. I tried hard looking for some information on this meter, but the manufacturer doesn't tell anything and their support forum was quiet (I commented on another post in their forum that was asking the same thing). So I opened the meter up and found six trimmer resistors. All trimmers are labeled VR1-VR6, so it's easy to find them. VR1 and VR5 are hidden below the display on my specimen. It seems that on later models, VR5 is just below the power switch and only VR1 is hidden. I began adjusting...