Hi Gus, Are the pulses 8ns long or are you saying they are much longer but you need to know the pulse width to within 8 ns? You will need to be concerned about not only sampling rate but also rise time (which is directly related to bandwidth). If you need 8ns pulse-width resolution, then the rise time/fall time needs to be less than about 1/4 of 8ns. This is because the pulse your scope sees will be reduced (in width) by 1 rise time and 1 fall time. You want this sum to be less than half of your required resolution. 1/2 times 1/2 =3D 1/4. So, 2 ns rise time. It takes about 3 time constants of a first-order system to rise (or fall), so you need a 2/3 ns (666ps) time constant. Bandwidth is approximately equal to 1/(2*pi*Tc) where Tc is the time constant. So, you need 240 MHz bandwidth at the probe tip. In other words, the total bandwidth of your circuit driving your probe driving your scope must be 240MHz or more. Then, you want the sampling rate to be 5 times this (if you don't want to do anything fancy) or if you are willing to do some careful interpolation between samples, you could get away with 2 or 3 times 240MHz. So, you are probably looking at a 1GSample/sec, 240MHz BW scope. The good news is that almost all modern digital storage scopes have sampling rates higher than 1 GSample/sec. The bad news is that the cost of one that can do 250MHz BW is much more than the typical low-end 100MHz or 60MHz model. Also, you will need a fast probe, perhaps even an active probe, to get this. It is pretty obvious, but I would look at Tektronix, Agilent, and LeCroy scopes. I have never rented one so I do not know how much that costs - I'm sure it's pretty costly. You could probably buy a used, working scope which is capable of this for about $1000 to $2000: Check out the following eBay items: 280389126103 LeCroy 9350AM Oscilloscope, Digital: 500MHz,1GSa/s,2ch buy it now $1200 200348744074 LECROY 9370M DIGITAL OSCILLOSCOPE DUAL 1GHz + PP062 (w/1GHz probe) buy it now $2000 160352930409 HP AGILENT 54520A 500 Mhz, 2 Channel Oscilloscope (warning: as-is) buy it now $650 or best offer 200318155708 LECROY 9354AM DIGITAL OSCILLOSCOPE QUAD 500MHZ 2GSa/s buy it now $1580 390087113847 TEKTRONIX TDS380 400 MHz 2 GS/s DIGITAL OSCILLOSCOPE buy it now $950 Are these pulses always the same amplitude? There are other kludges you can do to get a pretty good handle on the pulse width without actually sampling them. For example, you could measure the average signal voltage during an interval, along with how many pulses there were in that interval, and then get the average pulse width from that. You could also build a little circuit which used a very fast comparator to charge a capacitor during the pulse on time. After the pulse was received, the voltage on the cap would be proportional to the on time. 1nsec comparators are obtainable for about $5, but there would be considerable design skill needed to get the whole circuit working right. Sean On Fri, Aug 28, 2009 at 6:44 PM, AGSCalabrese wrote: > The waveform is repetitive NOT. > Any recommendations on a scope to rent ? > Gus > > >> On Aug 28, 2009, at 3:40 PM, Bob Blick wrote: >> >> >> On Fri, 28 Aug 2009 15:31:00 -0600, "AGSCalabrese" >> said: >>> I will be required to measure an analog pulses to a resolution of 8 >>> nano-secs. >>> Am I correct that this will require a scope that has a bandwidth of >>> 250 MHz and a sampling rate of 4 nanoseconds ? >> >> Bandwidth and sampling rate are not neccessarily tied to each other, >> so >> different scopes will have different correspondences between them, and >> if you are measuring a repetitive waveform you can have a slow >> sampling >> rate and still yield good results(assuming a quality instrument). I >> have >> a scope here with the same sampling rate as bandwidth and another with >> five times the sampling rate as bandwidth. >> >> Cheerful regards, >> >> Bob >> >> -- >> http://www.fastmail.fm - Or how I learned to stop worrying and >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0love email again >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist