How to measure Voltage & Current with a single multimeter, Simultaneously?

Question

I have bought a cheap but neat Uni-T UT61E multimeter, which only has one display as most multimeters. For 40 Euro's I cant complain. It's on the way to me.

Q.1 If I would like to measure both Voltage and Current, do I have to buy another multimeter? Are there mutlimeters that measure both Voltage and Current in two displays with multiple wires attached to the meter? Have searched but haven't found any hand-multimeter.

Q.2 I would like to put a very tiny voltage/current multimeter lcd on my batery pack so that I can check the volage there (without using my big multimeters) on travels. Any advice on how/where I can find such things? So far I only found this which is a self-build kit:
Do you have better advice and/or know any existing final products that are calibrated and working okay?

http://www.electronics-diy.com/store.php?sel=kits&sub=pic_voltmeters

My new big mutlimeter on its way, with which I guesse I cant view voltage and current simultaneously:

Answer 1

Q1. They do exist, but they are (much) more expensive. In most cases you can measure a fixed battery voltage and continue to assume that voltage while measuring current. Or, you can buy a meter with a dual display, but those typically aren't cheap. Most dual display meters though can't do everything you need - for example, they can only measure voltage and frequency at the same time. I'd suggest what you do instead is keep the nice meter for accurately measuring most things but buy one of the cheapie Mastech £3 meters to measure the second quantity. They actually do pretty well, most within 0.5% accuracy. And it's no big deal if you damage one.

Q2. I've heard good reviews from this one, designed for model aircraft.

Answer 2

To anwer your first question:

If you want to measure both current and voltage at the same time, you're doing a power measurement. A typical multimeter has no support for that. To do accurate power measurements, your best bet is to use 2 multimeters at the same time.

If you use 1 multimeter and swap V/I in 2 tests, you may get a little error due to the internal resistance of the multimeter in the Amp range. That might lower the voltage on your load, which may increase current depending on the type of load (switching supplies draw more current with lower input voltages).

Answer 3

You do not need to measure voltage and current in Your loader simultaneously. They do not change rapidly in Your loader/battery set. You can simply measure Voltage, then current. By me, it is better to buy good quality Charger and batteries, than carrying multimeter with You.

Answer 4

I often just use two or more multi meters to measure voltage and current simultaneously. I just note the results down by hand periodically, and calculate a rough figure for power draw over time. For more professional purposes, you can get data logging equipment such as Trendeca that can simultaneously log voltage, current, and a whole host of other parameters. This type of equipment is expensive, but produces better results than I can get by hand.