Why do digital multimeters not have zero-blanking?

[HighVoltage]

The leading zeros are annoying and when I asked Keysight a while back, they did not even have a good answer for me.

But, what is even more annoying is that the modern Keithley DMM7510, 2450SMU and so on, do not have a 1000 separation. At least Keysight has implemented this correctly on the 34470A and others.

[bd139]

Just confirmed, two thurlby Thandar power supplies (ts3022/pl310) and a 1705 DMM do not have leading zeros. Well done 

[floobydust]

The International System of Units (SI) and ISO 80000 seem to have not defined it, all I find is:
5.3.4   Formatting numbers, and the decimal marker
"... If the number is between +1 and -1, then the decimal marker is always preceded by a zero."

Fired off an email to International Bureau of Weights and Measures expect to hear nothing as a small fish in the world of committees.

NIST Special Publication 330 they follow SI too.

It's all kind of hilarious.

I could book a trip to Geneva to protest.

[Benta]

"... If the number is between +1 and ?1, then the decimal marker is always preceded by a zero."

I expect it should read:

"... If the number is between +1 and -1, then the decimal marker is always preceded by a zero."

So what's your problem with this?
To me it makes perfect sense. Unless you think that .987 is the right way, of course.
I'd always use 0.987

[floobydust]

"... If the number is between +1 and ?1, then the decimal marker is always preceded by a zero."

I expect it should read:

"... If the number is between +1 and -1, then the decimal marker is always preceded by a zero."

So what's your problem with this?
To me it makes perfect sense. Unless you think that .987 is the right way, of course.
I'd always use 0.987

Typo, cut/paste changed "-" to "?". One leading zero is A-OK no problem.

It's the double-0 crap I can't stand, damn James Bond

[steve30]

My Thurlby 1503 suppresses some zeros but not others.

Code: [Select]

   .00
   0.0
  . 00
   .00
   0.0
  . 00

Basically, its zero reading is 00 and the range switches just move the decimal point.

Thinking about it now, this actually looks quite odd, but I've always found this meter quite easy to use so no issue for me.

[Halcyon]

This reminds me of some "genius" at work who decided to create their own "asset labels" using a regular label maker and stuck them on absolutely everything, rather just recording the corporate-provided asset numbers on the important (valuable) stuff and/or model/serial/part numbers of equipment.

Next time I went to use the paper shredder, that person had stuck a 30cm long tape label (I'm not exaggerating) with "Asset # 000000000123456789" on it.

[CopperCone]

once you use a instrument for a while its nice to be able to instantly tel what the fuck its doing based on the display (how its set etc).

zero blanking seems fucking annoying

the 3455a seems bad too, nice to have higher confidence (easier to see the zero rather then just the decimal), not to mention a bunch of segments need to break rather then 1 segment to cause a error reading

[Assafl]

Leading zeros are not misleading... All they tell you is that you that you are losing bits in your A/D conversion. Blanking leading zeros makes sense for low digit counts (like 3.5 digits). For high resolution devices it solves the question of how to display both the reading and the range at the same time.

As an example, if one were to measure using a 6 digit DMM and get a reading of 000.0158V one knows one should re-range the DMM. It could have blanked leading zeros or even converted to 15.8mV - but at that point one would have to deduce (using reasoning) that we are getting only 3 digits of dynamic range out of 6 possible digits. With leading zeros - this becomes plainly evident.
 
For some devices knowing where you are in the range is extremely important - a great example of this of the inaccuracy of the HP34401A at low (under 20% or range) AC volts reading. For the 34401A on ACV, a few leading zeros and one needs to exercise caution....

   

[amspire]

Leading zeros are not misleading... All they tell you is that you that you are losing bits in your A/D conversion. Blanking leading zeros makes sense for low digit counts (like 3.5 digits). For high resolution devices it solves the question of how to display both the reading and the range at the same time.

Yes. I think the main reason is so you immediately see that you are running way below full scale. You might not realise you are on the 1000V range when you are reading a 10V reference on some of the 7 1/7 or 8 1/2 meters. These meters often have many different modes with different levels of precision and so it is not at all obvious without the leading zeros.

If you are reading near full scale, the problem disappears as you are using all the digits. It is only an aesthetic problem if you are reading way below full scale and the makers of these meters are favouring clarity over aesthetics.

The main clue to this is that if you have a 7 1/2 digit meter and you are running it in a high speed mode that only gives 4 digits of resolution (if it has one), they do not show all 8 digits. They only show 4 digits.

[Dr. Frank]

The very first high resolution voltmeters, having a digital display, and originating from the early 1960ties, were these DVMs, Differential Volt Meters, like the Fluke 803 (from 1962, see picture), 883, and so forth, and calibrators like the Fluke 332A, 335A, HP 3420A and similar.

As they were operating mechanically, zero blanking was of course not possible, see picture of a 332B.

I assume, that this habit was simply taken over to the later true digital operating voltmeters and calibrators, until today.


Meters for analog units (V, A, Ohm) have fixed ranges, usually 5 per mode, and their resolution is usually fixed, e.g. 4 1/2 .. 8 1/2 digits.

Frequency and time counters in contrast, do not have such fixed ranges. The result is displayed in a 'floating' engineering or scientific format with exponents, so that trailing zeros do not exist. The number of digits is varying, and determined by the gate time of these counters, though.

Due to these differences, the display formatting was always done differently, over the history of these instruments.

[Brumby]

I don't think anyone can claim they are misleading - just that they are an impediment to quick recognition.


At least they are to me.

[tooki]

Leading zeros are not misleading... All they tell you is that you that you are losing bits in your A/D conversion. Blanking leading zeros makes sense for low digit counts (like 3.5 digits). For high resolution devices it solves the question of how to display both the reading and the range at the same time.

Yes. I think the main reason is so you immediately see that you are running way below full scale. You might not realise you are on the 1000V range when you are reading a 10V reference on some of the 7 1/7 or 8 1/2 meters. These meters often have many different modes with different levels of precision and so it is not at all obvious without the leading zeros.

If you are reading near full scale, the problem disappears as you are using all the digits. It is only an aesthetic problem if you are reading way below full scale and the makers of these meters are favouring clarity over aesthetics.

The main clue to this is that if you have a 7 1/2 digit meter and you are running it in a high speed mode that only gives 4 digits of resolution (if it has one), they do not show all 8 digits. They only show 4 digits.

This is a really good point.

From a usability standpoint, though, there's lots of merit in the quick recognition aspect of zero blanking.

But honestly, it doesn't have to be either/or. For example, Keithley bench meters with VFDs (other brands as well, maybe?) already use dimmed digits in their menus. Why not dim the leading zeros, so they're there, yet quickly identifiable as being zeros at a glance?

In general, I wish there was a bit more attention given to the fast readability of numeric displays. In this regard, I really like the font that Rohde+Schwarz uses on its recent LCD devices. But also, I'd love to see larger displays, period. With modern display tech, this can't be that hard.

[schmitt trigger]

Leading zeros are not misleading... All they tell you is that you that you are losing bits in your A/D conversion.  For high resolution devices it solves the question of how to display both the reading and the range at the same time.

As an example, if one were to measure using a 6 digit DMM and get a reading of 000.0158V one knows one should re-range the DMM. It could have blanked leading zeros or even converted to 15.8mV - but at that point one would have to deduce (using reasoning) that we are getting only 3 digits of dynamic range out of 6 possible digits. With leading zeros - this becomes plainly evident.
 
 

Now that you explain it that way, it makes a lot of sense.

Next time I see such a display, although it still be annoying, at least I will understand the information the DMM is trying to present me.

[StillTrying]

I'm afraid that if a "999.999" max. display was only showing  "    15.8" mV I wouldn't need all the extra zeros to know it's only using a small part of the resolution. 

[Muttley Snickers]

I found a solution, no need to thank me, it's what I do.   

[Brumby]

You would think in this modern era, someone could put an option in a setup menu somewhere where you can select what you want..

[rdl]

Just like you would think an option to select the colors of an oscilloscope's traces would be easy, but no. Most of them stick you with strange colors like yellow and pink.

[Retep]

One reason I can think of for not blanking the leading zeros is so you can see when a digit is not working. How misleading a non-working digit can be can be seen in this video: .
Having a non-working digit is not that unlikely with older equipment, however with modern (bitmapped) displays this should be a non-issue.

In the case of the HP 3455A meter I posted previously, I really wonder why HP decided to suppress the leading zero just before the decimal point. It doesn't seem to be a technical limitation since there is a digit available directly at left of the decimal point and the unit is microprocessor controlled.

[RoGeorge]

- To make sure the most significant digits are working, so you won't read 30.000 Vac instead of 230.000 Vac because of a faulty digit.
- To easily approximate the expected range/resolution

[madires]

One reason I can think of for not blanking the leading zeros is so you can see when a digit is not working. How misleading a non-working digit can be can be seen in this video:. Having a non-working digit is not that unlikely with older equipment, however with modern (bitmapped) displays this should be a non-issue.

They could have added a display test at power-on 

[StillTrying]

- To make sure the most significant digits are working, so you won't read 30.000 Vac instead of 230.000 Vac because of a faulty digit.
- To easily approximate the expected range/resolution

On a quick glance 830.000 Vac often looks like 030.000 Vac.

[IanMacdonald]

The origins of leading zero blanking lie with LED calculator displays, where displaying 00000025 used four times as much battery current as displaying 25.

There weren't that many LED DVMs, and they mostly were 1999 displays anyway. So it probably didn't matter so much there.

[RoGeorge]

On a quick glance 830.000 Vac often looks like 030.000 Vac.

"Life is hard, and then we dye."

[bitseeker]

I find the extraneous leading zeroes disturbing, especially on professional-grade equipment. They increase the cognitive load when reading a value on the display, which is not desirable on a technical instrument. Although there are many seemingly plausible hypotheses as to why the practice persists, I don't find them to be all that compelling and they've mostly been debunked in this thread.

Unnecessary leading zeroes seem to me to be more a case of The Pot Roast Principle. Keysight's response when queried about their inclusion of extraneous zeroes tends to support the notion.

Unfortunately, adding options or breaking the status quo takes time, time costs money, and companies tend not to spend either unless (they believe) it will make them more money.