I am designing a more high tech one. It will have a USB interface, colored LCD and as many bells and whistles as I can fit on it. I plan on selling it for over a hundred.

 

Okay? So how do you plan to isolate the USB output well enough to handle being connected to a 1000 volt line at the same time?

 

Did not think of the 1000 V's with about 4 to 5 inches of separation could cause damage to the USB serial port. Isn't that enough space for clearance?

 

Okay? What is the USB port connected to internally as in what purpose does/will it serve?

 

Basically interface with a computer to transfer the data on the multi meter to a PC with some custom software.

 

And will this interface be connected while the meter is doing actual live line connections?

BTW, Here's just one of dozens of your present competitors already on the market and for only $60.

http://www.homedepot.com/p/Dawson-Digital-Multimeter-with-USB-Interface-DDM230B/206537423?cm_mmc=Shopping|THD|G|0|G-VF-PLA-D27E-Electrical|&gclid=CI6GqYntu8wCFZE0aQodPI8G0w&gclsrc=aw.ds

YouTube instructional video

 

That would be the plan. The 1000 V will be reduced by high voltage precise resistors(voltage divider) before it interfaces with the ARM processor.

 

And how do you plan to isolate both the multimeter inputs and their circuitry from the four lines that go out from the USB into the computer?

In order to do live line testing the USB signals need to have full isolation from the internal circuitry of the multimeter that is doing the actual measuring and converting of signals to the digital format that it sends to the computer via the USB connection.

To be honestI am thinking you are way in over your head both technically and financially to make such a device that you can legally sell anywhere let alone at a competitive level with existing devices already out there.

Here's the basic 'White Paper' specs for meeting basic electrical category standards.
http://www.ni.com/white-paper/5019/en/

And more info on the why of it all.
http://ecmweb.com/content/does-your-meter-safety-measure

UL related specs to meet.
http://ecmweb.com/archive/what-you-need-know-about-category-ratings

UL certifications costs.
http://www.referenceforbusiness.com/small/Sm-Z/Underwriters-Laboratories-UL.html

Figure around $8000 per certification number and a device like your may need to have over a dozen different certifications to be legally marketable .

My rough guess of what it will take to design the device you want to work the way you want and be legally marketable will push the near half million dollar investment level before a single device hits the shelf anywhere.

 

To be honest my plans only exist for developing a prototype and then seeking help regarding the UL certification process. I am aware of other manufacturers that have existing designs. None use a color LCD and touch screen because probably of the BOM cost. I just enjoy working on electronics it is my hobby. So time going into code development and PCB design is high quality time. The plasitic mold injection for the case is another problem I might not be able to tackle.

 

My suggestion would be to buy one or more of the mass produced units and dissect them to learn exactly how the pros are building theirs and why and then figuring out their weak points and improving on that.

You will be time and money ahead by dong so.

Here's your baseline competition for a full touch screen multimeter with lots of bells and whistles as well.
http://trends.directindustry.com/shanghai-yi-hua-v-instrument-co-ltd/project-156613-125893.html

 

They are rated at only 500 V but they have no rotary switch. How they do that. Using semiconductor switches.

 

That's for you to figure out.