Is there such an instrument, similar to an oscilloscope, that displays a history of voltage and current (like a heart-beat monitor). Oscilloscopes don't do it for me because they just show instantaneous wave forms.
As an example use; I'd like to have a circuit that consisted of motor, switch and power supply being measured by this instrument. When I close the switch, activating the motor, I could look at the instrument, and see how much current was pulled from the supply and in what way. It would look like a large dip in the line graph. I'd also be able to see how the voltage fluctuated, historically. Does such a device exist?
The problem with a histogram is that you might know that the low current was 0.5 A and the high voltage was 10.0 V, but you wouldn't be able to tell if they happened at the same time.
There are power meters that present this kind of data. It is intended to make sure that your CDMA signal has the correct distribution of powers.
I have heard of DMMs with outputs on them, which you could hook up to a data logger.
with two of them, you could track both voltage and amps and log the data and graph it.
I am sure it wouldn't be too hard to set up either.
Neight:
I have heard of DMMs with outputs on them, which you could hook up to a data logger.
with two of them, you could track both voltage and amps and log the data and graph it.
I am sure it wouldn't be too hard to set up either.
THe problem is, before I shell out the money for any of this stuff, I need to see proof that it has the specific, specific functionality that I'm looking for. What is the type of display mode that I described even called?
What time frame of measurement? Do you need instantaneous display, or would 10 seconds later be OK?
Arduino has analog inputs. If you can use them to measure the voltage and current, you can either sent text data to Excel or other spreadsheet for graphing, or to "Processing" to make graphs.
David82:
THe problem is, before I shell out the money for any of this stuff, I need to see proof that it has the specific, specific functionality that I'm looking for. What is the type of display mode that I described even called?
What you are describing is simply a datalogging application. The details are mostly in the input capablities you are requiring, the storage depth you have available (not an issue with modern PCs usually) and the speed of sampling you require. There are many ways to accomplish such a task(s) and it may or may not require an arduino, although that tends to lower the costs a lot if the arduino's 10 bit ADC, sampling speed, and max serial baud rate speed meets your requirements.
So it's your requirements that point the direction to the 'best and proper' selection of components and software, with maximum sampling speed being among the most important specification only you can provide.
So go download Simplot. Free. Will show you the basic waveform you want.
If Simplot doesn't do 1-shot capture, then you will need to buy something like DPScope, where you can set a trigger level that the scope will capture data on when the level is reached.
You will also need a "current probe" if you want to measure current levels.
I did some more googling. It seems that what I'm looking for is a Graphical Digital Multimeter. It displays a historical graph of measured data. Not 100% sure yet though.
The Fluke 287 / 289 seems to be the more preferred version of this type of DMM. The problem I have with oscilloscopes is that I'm not confident they have that same mode. I've never seen any evidence that they graph the way the graphical DMM does.
David82:
The Fluke 287 / 289 seems to be the more preferred version of this type of DMM. The problem I have with oscilloscopes is that I'm not confident they have that same mode. I've never seen any evidence that they graph the way the graphical DMM does.
The DSO203 is NOT 72MHz analog bandwidth, despite the fact that -everyone- selling them claims it.
The capture speed is 72Msps (mega samples per second), but that is divided among the channels in use and is NOT the bandwidth. For an analog signal like a sine wave, you really need 8x or greater samples per second than the frequency of the sine wave.
So to use the two analog channels, it is really a 4MHz 'scope. Not bad for such a tiny little thing, but it is -not- 72MHz.
This is born out by the antialiasing filters on U17 and U18 on the two analog channels which have a -3dB cutoff of about 4.4MHz.
Channels 3 and 4 are digital inputs only. I think they require CMOS logic levels to trigger. If your signal is less, nothing shows. Those channels will not display anything but square waves. So they are useless for troubleshooting a digital signal for ringing, undershoot, etc. In addition, using all four channels brings it down to 18Msps capture per channel, bringing the bandwidth down to about 2MHz. Add to that, there is a manufacturing error on the digital inputs that slows their frequency response down to about 1MHz bandwidth due to excessive capacitance from a couple of TVS voltage protection devices.
If I'm looking at a digital signal with a scope rather than a logic analyzer, I'm looking for things like ringing, overshoot, undershoot, etc. For that, you really need a scope with a bandwidth at least 10x the square wave's base frequency. Or you can calculate it based on the rise time of the wave. In that case, the minimum bandwidth is 0.4 divided by the rise time. That is the number used for digital scopes, often, whereas for analog scopes we usually use 0.35 divided by the rise time.
Why modern DSOs with flat response lowpass filters should use 0.4 instead of the 0.35 used with gaussian lowpass:
