This question draws upon elements of using a DVM for AC. My multi meter has a 1000V – 200mV AC range. Since there seems to be a consensus that multi meters can only reliably read 50Hz AC wave forms, why would you have this range on a meter? Very few are going to use a 50Hz signal for testing their kit. It might not even get through some small coupling capacitors. It doesn't really get to /from my sound card which I'm using as an oscilloscope. So unless you're measuring the mains, what's the point of such a huge AC range on my meter? In what circumstance would you be needing to measure for example 100 mV AC @ 50Hz?
Electronic – the 1000V – 200mV AC range for on the multi meter
acmultimeter
Related Solutions
What features give reason for such a wide range of prices for digital multi-meters?
THE most important feature is stability aka the voltage reference internal to the device. A lot of really good multimeters use the LTZ1000. Here's a picture: -
Notice how the device is mounted on spindly bits of PCB legs to avoid stress on the die causing random ppm shifts in the output voltage. If you read up on it you'll also find that it has a resistive heat generator and temperature sensor internally so it can be oven controlled.
The LTZ1000 boasts temperature drifts of 0.05 ppm per degree centrigrade. The best "off-the-shelf" device I've found is a maxim device at 2ppm/degC or the LTC6655 also at 2 ppm/degC. Long term stability is also top of the list when it comes the the voltage reference.
Next is very tight precision low drift resistors in fact matched resistor pairs like you can get from Vishay and Linear technology. These are not cheap and turn a run-of-the-mill meter into something like a decent fluke or HP meter.
Forget features - they are ten a penny in comparison.
Some multimeters have a diode tester so you could use that on any number of LEDs to find their forward voltage. This may not work on adressable LEDs. Other than this you can try to identify the LEDs and Google them to find the spec sheets Fv at the least, but bear in mind that this is usually fairly inaccurate but it could be your only option.
You could also check the output of the PSU for the LEDs and go from there about a correct supply voltage.
If I needed to test the pinout I would:
- Try to find a schematic in the manual
- Tap each contact with a lesser supply voltage till you get lights
- Attempt to find the schematic and specs of the IC that is being used to make the LEDs adressable throughout the strip. This might also reveal the reccomended input as I would hope the ICs had a constant current driver (better running conditions for an LED than contant voltage).
Hopefully this is what your looking for!
Best Answer
I have owned and used a large number of DMMs during my engineering career, and have calibrated the AC range against frequency on most of them.
The suggestion that the AC range on DMMs only reads 50/60Hz has elements of truth. A more accurate summary is that the AC range on all DMMs will read 50/60Hz, many DMMs will get to 1kHz, a few will cover the full audio range, and it's a rare beast that will read accurately above audio.
Not surprisingly, the cost of the meter has some correlation with the frequency range it can achieve. Also note that an audio range DMM will always specify this, as it's a cost-adding feature.
Given that to calibrate the frequency response, you need access to test gear that most amateurs do not have, the safest course of action is that, if your meter doesn't specify otherwise, only trust it at mains frequencies.
So, given that all meters will measure AC mains frequencies OK, why do you need 1000V to 200mV? You need 1000V to measure the mains coming in at the wall. Caution: this is not enough to be safe, you need a CAT2 or CAT3 protected meter to safely withstand (that is, fail safe) when hit with the all too common over-voltage spikes on mains supplies. People have died using a non-CAT meter on mains, even on the 1000V range.
You need 200mV to measure the voltage drop on a wire, across closed contacts, or a current shunt. Thanks to Chris for pointing out that there are plenty of intermediate AC voltages, like transformer secondaries, for which the 2v, 20v and 200v ranges are appropriate.