Hi,
I want to choose high accuracy high resolution multimeter.
First I want to say that I make the difference between resolution and accuracy. I know that most high resolution multimeters' accuracy do not cover last digits (at least cheaper ones). But resolution is good even if accuracy is lower.
So what I need? First about accuracy - mission impossible. Everyone wants cheap and good stuff. Yes, I know that there is no full happines, but I can't spend $1000+ for high accuracy multimeter. Second - accuracy on what - mainly DC voltage, but also resistanse. DC current accuracy would also help, but it could be a little bit lower.
What I'll use the multimeter for. Calibration of voltage references and opamp circuits for ADC/DAC, sensors and others. I can't calibrate a voltage reference that's by specification 0.4% any further if the best accuracy multimeter I have is 0.5% (MASTECH MS8220R).
Resolution? Well it's useful thing to have. To measure small changes ... etc. If I have to choose I would sacrifise resolution for accuracy of course, but most cases for a price ragnge accuracy is the same.
My idea is to use combination of multimeter and fairly accurate voltage standard from
http://www.voltagestandard.com/. Depending on the situation I will use either the multimeter or the voltage standard + multimeter to measure the difference.
Additionally it would be great to have double display - measuring 2 things at the same time is quite useful - min/max when averaging, frequency when measuring AC voltage. It
must have relative measure. The display should be 7 segment, clear, easy to read, not dot matrix. I don't like fancy digits and graphs in multimeter. Most of them have PC connection for that.
I'm not yet mentioning the price because I don't know yet what are the options, but it should be not much more than 200USD.
I looked at these models:
BRYMEN BM867 DC accuracy - 0.03%+2 digit, 50,000 counts + 500,000 counts mode (
)
BRYMEN BM869 DC accuracy - 0.02%+2 digit, 50,000 counts + 500,000 counts mode
UNI-T UT71D DC accuracy 0,05% + 5 digits 40,000 counts
I haven't looked at stationary multimeters ... mainly because they are expensive, they are bigger and have the same accuracy for higher price. I guess lower priced stationary multimeters aren't that great.
There is something else. Most of these multimeters have working temperature range quite wide. There might be slight difference between the cheaper ones and brands like Fluke, Agilent of how they specify accuracy. They should all specifyaccuracy in full temp. range, but do they? We saw before that specs not always match for lower priced brands. Yes, they are compensated, but I'm sure that accuracy change a bit with temperature. So my guess is that accuracy should be slightly better at room temperature.
So go on. Tell me how bad desision I'm making when I think of buying lower quality brand ... and thanks in advance.