Time mark generator for calibration analog oscilloscope (make or buy help) - Page 1
Forum section: electronics / testgear

author: circuitravi
author_rank: Contributor
timestamp: December 21, 2015, 05:17:42 am
content: I want a time mark generator to calibrate my analog oscilloscope. marker outputs, two nanoseconds to one milliseconds and trigger output one millisecond. please help me to buy or make a time mark generator. thanks!

author: tautech
author_rank: Super Contributor
timestamp: December 21, 2015, 06:28:26 am
content: Quote from: circuitravi on December 21, 2015, 05:17:42 amWelcome to the forum.These are a pretty specialized bit of gear, what makes you think you need one?Have you made major repair/changes to the scope?Tek and Phillips made some of the calibrators most commonly used and some Tek unit #'s from a google search are: 184, TG501, 2901. Phillips had a 100 Mhz unit and a mate owns one if/when I ever need it but I'm sorry I don't have the model #. PM something.Unless the scope is WAY out of Cal it's likely you can adjust it for quite satisfactory accuracy for most use.Dave checked and adjusted a Hameg in this vid:http://www.eevblog.com/2013/08/03/eevblog-502-19-hameg-analog-oscilloscope/

author: tautech
author_rank: Super Contributor
timestamp: December 21, 2015, 07:09:53 am
content: Found it:Phillips PM5771 with adjustable rise and fall range from 2.4 ns to 100 us in 4 fine adjustable ranges.It is a dedicated 1 Hz to 100 MHz pulse gen.

author: Smith
author_rank: Frequent Contributor
timestamp: December 21, 2015, 07:29:44 am
content: Some FG/pulse generators will do just fine. Even a simple FG with square wave output can be used to test amplitude and frequency on an analog scope. I normally set the timebase to 2 divisions, which works like a charm for testing.Sometimes I see the analog scope calibrators showing up on eBay or local sites. Most are to slow for >50MHz scopes, or they are to limited in use, or to damn expensive.

author: circuitravi
author_rank: Contributor
timestamp: December 21, 2015, 07:31:24 am
content: i have tektronix 7704a oscilloscope. i want to calibrate it. as per manual it need a time mark generator like tektronix 2901 time mark generator. is this calibrate using function generator? please help me.

author: tautech
author_rank: Super Contributor
timestamp: December 21, 2015, 08:41:57 am
content: Quote from: circuitravi on December 21, 2015, 07:31:24 amYes if you NEED to adjust it to be completely accurate.Simple checks of accuracy can be made using a FG but of course you need to know if the FG is accurate before you start. It is the same with a time mark generator, for accurate Cal procedures it too must be in calibration.You have not said what parameter needs adjusting, amplitude or timebase?There are ways to do checks without the "specified" Service manual equipment but a good understanding of how CRO's work is needed.A link to the Service manual you have will help us to devise another method to accomplish the checks you need to make.

author: tggzzz
author_rank: Super Contributor
timestamp: December 21, 2015, 10:26:57 am
content: Quote from: circuitravi on December 21, 2015, 05:17:42 amFirst you need to define how accurate the time intervals need to be. Analogue scope's specifications are usually 1% or 2%.You will probably find that the horizontal sweep is defined by a set of resistors and capacitors. It is unlikely that every timebase range uses different capacitors and resistors: usually they select different combinations of a small number of resistors and capacitors. If that is the case then you don't have to test every timebase range, you can test a suitable subset. At aguess, you might find that you can You will have to look at the service manual schematics to determine that.If you can get away with using clock periods of >10ns, then use a cheap TTL/CMOS crystal oscillator module, and divide the output using standard discrete logic.

author: Kalvin
author_rank: Super Contributor
timestamp: December 21, 2015, 10:45:07 am
content: Cheap, crystal-based function generator might do.

author: circuitravi
author_rank: Contributor
timestamp: December 21, 2015, 11:16:45 am
content: i have a service manual. when it comes to adjust geometry. it says,how this adjustment take place? is this can achieve using function generator? is they have maker output and trigger output? how can i arrange this time mark generator? thanks my dear friends......!!!

author: Smith
author_rank: Frequent Contributor
timestamp: December 21, 2015, 12:40:00 pm
content: A pulse generator is basicly a time mark generator with a lot more controls. Some frequency generators have pulse generator features too. A descent FG has way less than 100PPM output variation. A basic analog scope has 1 or 2 percent (10.000 to 20.000PPM!), so most FG's will do just fine. Only real need for a pulse generator (in stead of a FG) I can think of is to check the scopes ability to trigger on a small pulsewidth signal, or check it's ability to show small pulsewidth signals on screen.

author: circuitravi
author_rank: Contributor
timestamp: December 21, 2015, 01:35:55 pm
content: can i set pulse generator 1ms marks and 1ms triggers? is they have separate trigger control? thanks every my friend..!

author: tggzzz
author_rank: Super Contributor
timestamp: December 21, 2015, 04:34:03 pm
content: Quote from: Smith on December 21, 2015, 12:40:00 pmThat's true for synthesised FGs, but there are many analogue FGs, often based around an ICL8038.

author: circuitravi
author_rank: Contributor
timestamp: December 21, 2015, 04:37:13 pm
content: Most of the function generator hasn't a trigger output. ?Sent from my SM-N910C using Tapatalk

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 21, 2015, 04:38:31 pm
content: As noted, analog scopes are in the 2-3% accuracy range. If you have a synthesized function generator, that's probably close enough, but you may need to process the output if it doesn't provide pulse output. If you use an analog FG, you will need to hook up a frequency counter (that you can trust) to get an accurate frequency setting. TM generators generally produce narrow pips so you can check the sweep accuracy against the graticle. You can always feed a square wave through a one shot to produce a suitable pip.I built a TM generator out of a 20 MHz can oscillator, a bunch of decade dividers and a one shot. That was way more accurate than the scope. You could do the same thing with something like an arduino or rasberry pi in software as long as they use an accurate clock.At least for Tektronix, unless you've done major component replacement, it's unlikely the sweep is going to be off enough to matter.

author: circuitravi
author_rank: Contributor
timestamp: December 21, 2015, 04:58:54 pm
content: I need a trigger output? How can i achieve it? Thanks!Sent from my SM-N910C using Tapatalk

author: nixxon
author_rank: Frequent Contributor
timestamp: December 22, 2015, 03:26:02 pm
content: Quote from: Smith on December 21, 2015, 07:29:44 amI did it like you suggest when I was into this a while back. I made a waveform for my Siglent SDG1020. In my post there is also an txt.file and a screenshot of the signal on the scope:Quote from: nixxon on May 02, 2013, 07:29:00 pm