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[patsmx5]

Need one that can measure very low voltages, low frequencies. 5-6 Hz and up. Need to be able to datalog with it. Cheap is good. I think JD posted about one a while back but I couldn't find it. I got a fancy 2 ch 100mhz tech but it weighs 90 lbs and doesn't datalog.

[patsmx5]

Oh yeah, needs to be able to datalogg multiple channels. I'd say 4 to be safe, I know I'll need 3 minimum. More the better. And the voltages I'll need to measure are down to 20 micro volts, up to say 5 milli volts.

[rawr]

5-6 hz is kind of super fuckin low.  Do you really need that low?  Most shit starts at 20hz minimum at least for a reliable signal.

The rigol shit says it does 5hz, it may. idk how accurate it is I haven't touched one.

[patsmx5]

5-6 hz is kind of super fuckin low.  Do you really need that low?  Most shit starts at 20hz minimum at least for a reliable signal.

The rigol shit says it does 5hz, it may. idk how accurate it is I haven't touched one.

yeah, I know it's stupid low but that's where this thing will need to pickup. preferably go lower, but 5 is the minimum. I dunno if any of them will detect a 5Hz signal at 20 micro volts, but that's what I need.

[rawr]

what do you need the oscope for? This a mostly one time measurement deal or will this be something that you're using  a lot?


I may be able to hook it up if its just something dumb you need verified and can ship.

[patsmx5]

I'll be using it for a few months here and there as I do some testing/measuring and eventually for building and testing a circuit that decodes the signal I'm trying to datalog. I also want a good one just to have, as I have used my Tek Oscope several times, but 9 times out of 10 I need to be able to datalog for it to really be useful.

Also will need a signal gernator that can do signals as described. May need more than one, as I'll need 2-3 signals being generated that I can adjust to tune the receiver to pick out the right one.

Oh yeah, and I don't really know what I'm doing either, so this project might take a while.

[rawr]

I work with this shit all day big money 100k dollar boxes and you're going to be hard pressed to find shit that goes down that low 


My calibrator goes down to 20hz minimum. I've got a sig gen that will do 5hz.


Best thing for 5 hz, assuming you're doing car shit, is actually building a rotating assembly with the sensors mounted, a known good bench dmm and a stable power supply and actually create the signals how they would be in the real world using the sensors and a rotating mass. Or do shit at like 20-30hz then step the signal down in a real world app.

Use time/refresh rates to figure out the wave form and the offset.  idk, but there's ways to do it for cheap.

[JaredKaragen]

FYI ~2hz is the resonance frequency of a chickens skull... Enough amplitude and the brain turns to jello

Good luck finding one tho... That's a little twoards specialized gear

[t_cel_t]

is this an analog or digital signal?

the low voltages is nothing, every scope can pic that up.
4 channels and a way of saving it, thats where your looking at $5000+ for the cheapest scope.

if you dont need a visual, you could use an arduino and a datalogger shield, im not sure of the voltages needed but it will probably work. or you could throw together a board with a quad op amp and bump the voltages up to a readable level.
http://www.ladyada.net/make/logshield/lighttemp.html

[fe3tcourier]

You say that you don't know what you're doing. Thus I'll ask if they're analogue signals or not? If not, you want a logic analyser. They do 0.00000001 Hz to 20000000000 Hz just fine :-)

[rawr]

I still want to know what you're measuring at 5hz.


Weird accelerometer?  5hz is too slow for a trigger wheel or almost anything else.


Even if those sigs aren't digi he can use a adc

[E-b0la]

Something spinning at 300 rpm?

Ever look at some of the NI USB dataloggers? The NI USB 6008 and 6009 are pretty inexpensive, although they only have 12 and 14 bit ADC's so I'm not sure that's accurate enough for your application, but it could be since you are only measuring a window of a few millivolts.

You will need software for for them. You can get eval versions of labview. I'm not sure if there are any free versions of software for NI hardware.

[E-b0la]

http://www.ni.com/labview/signalexpress/

NI's Signal express limited edition is free, and comes with a 30 day full evaluation. I guess you can't use the analysis tools and such with the free edition, but you can save the data in some form excel can read and then do the analysis there.

[patsmx5]

I still want to know what you're measuring at 5hz.


Weird accelerometer?  5hz is too slow for a trigger wheel or almost anything else.


Even if those sigs aren't digi he can use a adc

I work in the oil field. We have a telemetry system used in drilling tools that go down hole to transmit data to the surface. One system uses very low frequency radio waves, actually goes down to 2-3 hz, but that data rate is uncommonly used. Typical 5-12 Hz. The signals are analog.

What I need is something that can datalog several channels. It doesn't have to display the data in realtime, recording it is fine. If I can record, then go back and "Play" it somehow or just look at the data in a text file, that's would be fine. I need to keep the signals analog.

Actually building a rotating signal gen isn't a bad idea.  That would actually be perfect for what I'm doing, as I could change the speed of the wheel to vary frequency, and the distance of the sensor to vary amplitude. Good call there. Might build the trigger wheel motorized so I can keep it turning a certain speed, or even better, turn it on/off at different rates to create different transients.

[rawr]

Yeah just find some dataloggers. Way cheaper than an oscope

[patsmx5]

Yeah just find some dataloggers. Way cheaper than an oscope

So who sells dataloggers that record voltages this low? I figured it would have to be a scope, no?

[rawr]

Opamp circuit with a datalogger or rs232 on a used bench 8 digit multimeter or data acquisition unit ( more expensive and requires cards but has many channels ) recommended agilent stuff

[patsmx5]

Opamp circuit with a datalogger or rs232 on a used bench 8 digit multimeter or data acquisition unit ( more expensive and requires cards but has many channels ) recommended agilent stuff

Oh yeah, and I don't really know what I'm doing

I'm guessing Opamp circuit to boost the signal? I requested samples of an amp for this and have them already. RS232 is a serial cable says wikipedia.

I have no problem amping the signal up first if needed so I can datalog it, but i have to be able to step it back down when I'm done with it so it's at its normal un-amped voltage.

[rawr]

Yeah just to boost the signal like a 10x probe on an osciliscope.

RS232 to data log with a computer from a bench meter instead of using a daralogger. There's lots of ways you can do this stuff.

Post on tt and ask jd or Fred of he's not busy

[patsmx5]

I do have a pos laptop I could use to datalog with. I guess I would need a rs232 adapter or something? I have an old laptop, it has a db9 serial, and of course usb ports too.

[E-b0la]

how many channels are we talking 4, 8, more?

[patsmx5]

At least 4. If it were limited to 4, I would probably be ok. If it only costed a bit more to have an extra channel or two, I would pay it so I don't have to worry about running out of channels. I would say 8 channels would be more than enough.