DMM, what it mean on ±(0.025%+5) ? - Electronic Circuits Projects Diagrams Free

VictorPS · 6th January 2008, 10:22 AM

I am planning to buy a new digital meter.

While reading on the spec, it show:

DC voltage range: 400mV, 4V,40V, 400V, 1000V
Accuracy: ±(0.025%+5)

Question:
what does it mean on ±(0.025%+5) ?

Thank you,

Brian Hoskins · 6th January 2008, 01:33 PM

Well, the 0.025% part means the multimeter reading will be accurate to within 0.025%. I think the number that follows is the number of counts - it's to do with rounding error and noise limitations.

Brian

ericgibbs · 6th January 2008, 02:00 PM

Quote:

Originally Posted by VictorPS

I am planning to buy a new digital meter.

While reading on the spec, it show:

DC voltage range: 400mV, 4V,40V, 400V, 1000V
Accuracy: ±(0.025%+5)

Question:
what does it mean on ±(0.025%+5) ?

Thank you,

hi,
Is the meter a 5 digit display, the Accuracy: ±(0.025%+5) usually indicates its a 5 digit.??? Lets know.

JimB · 6th January 2008, 04:57 PM

I would guess that the DVM has a 5 digit display (or 4 3/4 digit ie 399.99).

As for the +/- 0.025%, this is reasonably obvious, except that it does not state whether that is 0.025% of the actual reading, or 0.025% of full scale.

The +5, I assume this means that the last digit of the display could be up to 5 bits out.

So, if the meter were reading a standard 100.000 volts, it could display anything between 99.9 and 100.15 volts.
(400v range 0.025% = 0.1 volt, and add 5 bits to the last digit).

JimB

Leftyretro · 6th January 2008, 05:29 PM

Accuracy specifications can be very frustrating to figure out. Manufactures are of course in competition with others so such specs are important to their marketing efforts and not always totally honest or at least misleading.

Accuracy is not a simple specification where one number can totally describe the meters attributes and most don't publish their full testing protocol.

Typically you get what you pay for in this area and their is a reason the Fluke and HP (agilent) meters are so respected by both the pros and hobbyist.

Lefty

Brian Hoskins · 6th January 2008, 06:12 PM

Quote:

Originally Posted by JimB

I would guess that the DVM has a 5 digit display (or 4 3/4 digit ie 399.99).

As for the +/- 0.025%, this is reasonably obvious, except that it does not state whether that is 0.025% of the actual reading, or 0.025% of full scale.

With most DMMs it's usually a measure of the actual reading.

Brian

VictorPS · 7th January 2008, 07:29 AM

Yes, it is a 5 digit DMM.
http://www.uni-trend.com/UT71E.html

but how about the "+30"?
AC Voltage 4V/40V/400V/1000V (0.4%+30)

Do you think this model UT71E of (China made) DMM is good?
I have seen the actual thing, it look quite solid.
It can link to PC through USB or RS232 too...

ericgibbs · 7th January 2008, 09:24 AM

him
This is an extract from the user manual for your meter.

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6th January 2008, 10:22 AM	(permalink)
VictorPS	DMM, what it mean on ±(0.025%+5) ? I am planning to buy a new digital meter. While reading on the spec, it show: DC voltage range: 400mV, 4V,40V, 400V, 1000V Accuracy: ±(0.025%+5) Question: what does it mean on ±(0.025%+5) ? Thank you,

6th January 2008, 01:33 PM	(permalink)
Brian Hoskins	Well, the 0.025% part means the multimeter reading will be accurate to within 0.025%. I think the number that follows is the number of counts - it's to do with rounding error and noise limitations. Brian

6th January 2008, 04:57 PM	(permalink)
JimB	I would guess that the DVM has a 5 digit display (or 4 3/4 digit ie 399.99). As for the +/- 0.025%, this is reasonably obvious, except that it does not state whether that is 0.025% of the actual reading, or 0.025% of full scale. The +5, I assume this means that the last digit of the display could be up to 5 bits out. So, if the meter were reading a standard 100.000 volts, it could display anything between 99.9 and 100.15 volts. (400v range 0.025% = 0.1 volt, and add 5 bits to the last digit). JimB __________________ Experience is directly proportional to the value of the equipment ruined.

6th January 2008, 05:29 PM	(permalink)
Leftyretro	Accuracy specifications can be very frustrating to figure out. Manufactures are of course in competition with others so such specs are important to their marketing efforts and not always totally honest or at least misleading. Accuracy is not a simple specification where one number can totally describe the meters attributes and most don't publish their full testing protocol. Typically you get what you pay for in this area and their is a reason the Fluke and HP (agilent) meters are so respected by both the pros and hobbyist. Lefty __________________ Measurement changes behavior

7th January 2008, 07:29 AM	(permalink)
VictorPS	Yes, it is a 5 digit DMM. http://www.uni-trend.com/UT71E.html but how about the "+30"? AC Voltage 4V/40V/400V/1000V (0.4%+30) Do you think this model UT71E of (China made) DMM is good? I have seen the actual thing, it look quite solid. It can link to PC through USB or RS232 too... Last edited by VictorPS; 7th January 2008 at 07:31 AM.

7th January 2008, 09:24 AM	(permalink)
ericgibbs	him This is an extract from the user manual for your meter. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/ Last edited by ericgibbs; 7th July 2008 at 12:23 PM.