You do need a voltmeter for checking various things around the house and your ecig hobby, but everyone needs a 510 threaded ohmmeter, especially if you wind coils. This one does resistance and voltage. One socket is 510 male and the other female. To check your mod voltage, you just screw it on the mod like an atomizer and press the fire button to check accuracy. The female thread is for checking your coil resistance. Just screw on your atomizer and read the resistance. You can use it as a hands free base to hold your coil deck when you wind a coil.
4 out of 5 reviewers found it accurate. One didn't and the supplier swapped it out. Now, he's happy, too.
$9.95 from Amazon
http://www.amazon.com/iSmoka-eLeaf-...&qid=1411234548&sr=8-2&keywords=510+ohm+meter
A good cheap voltmeter that's widely used around ECF. It's $5.44 with free shipping. Harbor Freight also sells this and sometimes it's on sale for $3.99. I have about 5 of them around the house in convenient places for quick checks. They all still work after years of use.
http://www.amazon.com/DT830B-Digita...UTF8&qid=1411234808&sr=8-5&keywords=voltmeter
BTW, your Segelei 50W box mod has built-in protection against shorted atomizers, so you aren't in danger of a shorted atomizer. That's assuming it's this one.
http://www.eciggity.com/sigelei-50-watt-box-mod/
Features:
★ Low Voltage Protection
★ Low Resistance Protection
★ Input High Voltage Warning
★ Output Short Circuit Protection
★ Reverse Battery Protection
★ Temperature Protection
★ USB Interface Directly Charging
★ Removable Battery Replacement
Technical Specs:
Power Adjustable Range: 7.0w - 50.0w
Output Voltage Range: 3.6v - 8.5v
Atomizer Resistance Range: 0.2Ω - 3.0Ω
Battery Voltage Range: 3.2v - 4.2v
Supported Battery Type: 18650
Error-code:
Low Res=Low atomizer resistance(﹤0.2Ω)
Low-Bat=Low battery voltage(﹤3.2V)
HHHHHHHH=High input voltage(﹥5V)