1 Multimeter Spec Comparison

I wrote a small application for myself to play around with JavaScript and AJAX, and this is what I chose as a demo. Since it has become quite nice, I'd like to release it. Its plotting is done completely in JavaScript using JQPlot, which - by the way - is an incredible and incredibly easy-to-use plotting library. It generates very pretty plots and is totally versatile. I can only highly recommend it.

2 Get to the application

2.1 I want to get right to the application, where is it?

You'll find it here.

2.2 Source code

I've put the source code of the whole application up on GitHub. If you have any improvements, please feel free to contibute!

2.3 License

Definition files are under the Creative Commons BY-NC-SA license v3.0. My source code is released under the GNU GPL-3.

3 FAQ

3.1 Why does it not work with IE/Chrome/Opera?

I don't know. I do not use any IE/Chrome/Opera available to test with. So it might actually work, I just have no idea. If you have patches that do not break compatibility with Firefox, I'd gladly use them. My testing is done with Firefox 3, 4 and 5 (which all work). And if you use any of the above browsers and it does work, drop me a note and I'll include that in the "tested" list. I've already figured out that it doesn't work with Chromium, but really am too much of a JavaScript novice to debug this problem. If you would like to contribute, please see section 2.2, and check out the GitHub repository. If you submit pull requests there, I'd be more than happy to make it work on more browsers than just Firefox.

3.2 What browsers does it work with?

I've successfully tested:

• Firefox 3.6.12, 3.6.17, 3.6.20
• Firefox 4.0.1
• Firefox 5.0
• Firefox 6.0.2
• Firefox 8.0
• Firefox 10.0.11
• Firefox 40.0.3

Although I've only tested Firefox, other browsers (Opera, Chrome) imght work, as well.. Crappy browsers (MSIE) likely won't and I don't really plan on fixing that.

3.3 What are these measurements?

They're not measurements. They are only vendor specifications.

3.4 What if a vendor lies about the specs?

Then the plot will lie. I cannot evaluate how accurate vendor specifications are. If they're wrong, the plot is wrong. If you distrust a vendor, keep that in mind. Maybe I'll add a "vendor distrust" function in the future where you can always add x% + n to anything a specific vendor claims.

3.5 How dare you compare a Agilent/Fluke to Uni-T crap?

I do not have any prejeduce against China multimeters and I don't give a crap about if the backside of a multimeter says "Made in USA" or "Made in Malaysia". It all depends if the vendor can deliver what he promises. Some really great vendors have put incredibly crappy products on the market -- and some unknown vendors have some surprisingly good products. The problem is telling the cheap crap apart from the bargains. While I will agree that most cheap meters are absolute crap, one should be fair and compare the vendor specs in a neutral manner. Making a decision from plot results is up to the user.

3.6 Is this 24h or 1yr accuracy? At which frequencies is AC measured?

I usually type in the accuracy which is best (i.e. 24h at the optimum frequency). This can also be seen in the comments of the XML and if you type in a datasheet, please include this crucial information, too. For example if you click on the Agilent 34401A and hit "Export XML", for the ACV range you will see a comment: "24h, 10Hz - 20kHz".

3.7 Your specs for meter X are wrong! Where did you get them from?

Sources are included in the XML files. Click on the multimeter to get a reference to who typed the data in and what source the person got it from.

3.8 Please add meter Y!

Please add it yourself. It is really easy! First, export a XML from a already added device (click on the name and hit "Export XML"). Then copy and paste the XML into your favorite editor. It is really really easy to figure out how it works. Enter the data of your favorite device in your editor, save the file. Then go to the "Edit" tab, hit "Create Device". Copy and Paste your freshly created XML into the textarea, hit "Import Device". Presto! If you send me your XML file, I can include it into the website so others can use it too!

3.9 Why don't you just compare the multimeter specs?

Yes, of course. Let's compare the Fluke 87V (6000 counts) against the Uni-T 61E (22000 counts) in the DCV range. Here are the specs of the Fluke:

Range	Accuracy
600mV	0.1% + 1
6V	0.05% + 1
60V	0.05% + 1
600V	0.05% + 1

and of the Uni-T 61E:

Range	Accuracy
220mV	0.1% + 5
2.2V	0.1% + 2
22V	0.1% + 2
220V	0.1% + 2
1000V	0.1% + 5

It does look, from the numbers, quite clear: The Uni-T has more counts, the Fluke a greater baseline precision (0.05% compared to 0.1%). Which one is the better device? If you're reluctant to say "yes", you'd be right :-) The correct answer is: It depends. Let's look at a graph created by the MMPlot application:

So when measuring from approximately 1.6-6V, the Fluke is better. From 6V-16V, the Uni-T is the better choice. You can avoid such surprises by doing the plots before buying a device.

Of course, this comparison assumes that the vendor specifications are correct. Therefore, you always need to take them with a grain of salt. While well-known vendors which provide high-quality products such as Fluke or Agilent are known to really print worst-case specs (i.e. specs which are valid over the whole temperature range, humidity range, etc) other vendors are known to not do this. Therefore the comparison is a bit unfair in this respect. You have to keep it in mind and take vendor specifications with a grain of salt.

3.10 How is this useful for me? My device isn't included!

One feature that I paid a lot of attention to was easy user-extensibility. All device definitions are in XML and can be imported via runtime. So you can look at existing XML definitions (for example by using the "export" feature), copy them into your favorite editor, write one for a device you'd like to include, and "import" that device via copy/pasting the XML. If that defintion file meets the quality standard and you want it to be released under the Creative Commons BY-NC-SA license, you can send it to me and I'll include it into the application, so everyone profits.

3.11 What are the definition file quality standards?

Very easy: The XML has to be based on some official, readily available source (i.e. a datasheet PDF). Ranges are to be entered in the order they appear in the manual. Numbers are to be entered in the way they appear in the manual (this is to make verification much easier). This means: If a vendor writes "20nF" for a range, you'd enter "20e-9" instead of "2e-8" or "0.00000002". If a resolution is specified as 0.0001kOhm, you enter "0.0001e3" instead of "0.1".