Hp1741a oscilliscope 1volt square wave calibration issue - Page 1
Forum section: electronics / repair

author: Applemac
author_rank: Regular Contributor
timestamp: December 06, 2015, 01:21:43 pm
content: Hi was wondering if someone could help, when using the 1volt square wave calibration on the Hp1741a oscilliscope, the manual states you should get a square wave 5 graticules long. Mine is six graticules long and the end of it slighlty curves.I have tried ajusting the trace alignment but that dies not change the length or the curve of the signal any ideas?

author: cs.dk
author_rank: Unknown
timestamp: December 06, 2015, 01:43:25 pm
content: What is your timebase setting? The lenght of the square will depend on that.Trace alignment is for rotating the whole CRT. You should compensate your probes to get a nice squarewave.Have a look at Allan's youtube channel:EDIT: It was this video about compensation;

author: tggzzz
author_rank: Super Contributor
timestamp: December 06, 2015, 01:53:34 pm
content: Quote from: Applemac on December 06, 2015, 01:21:43 pmA picture would help, as would a specification for the probe you are using.Is the curve there if the input is grounded? If so then the problem is in the deflection circuits.The trace alignment is irrelevant to the probe calibration, and to any curve on the waveform.I wouldn't worry about the 5-vs-6 time difference, since that signal's frequency is not critical. Use a known frequency (probably crystal controlled) to calibrate each timebase setting according to the manual.I wouldn't expect the amplitude to be exactly 1V. All that matters is that it has a sharp edge.Ensure the scope's input capacitance is within the range specified for the probe, then adjust the probe to remove undershoot/overshoot on the waveform edges.

author: Applemac
author_rank: Regular Contributor
timestamp: December 06, 2015, 05:25:04 pm
content: I wanted to include a picture taken from my ipad but this forum doesnt except the photo format that the ipad uses.I wondering if its the probes supplied with the oscilliscope they look like cheepos theyre sp100b probes with a switch that show ref x10 x1 .

author: Cyberdragon
author_rank: Super Contributor
timestamp: December 06, 2015, 06:09:52 pm
content: Some probes simply don't work with certain scopes. Probes and scopes have different input impedances, that's why probes have adjustments to match their impedance to the scope. If the probe can't adjust within the range of the scope impedance it won't work.

author: Applemac
author_rank: Regular Contributor
timestamp: December 06, 2015, 06:34:32 pm
content: That makes sense, anyone have a surgestion of a good probe to buy for my hp1741a oscilliscope?

author: cs.dk
author_rank: Unknown
timestamp: December 06, 2015, 06:40:33 pm
content: Quote from: Applemac on December 06, 2015, 05:25:04 pmConvert to a standard JPEG-file. Note the maximum filesize. Resize the picture to 1200-1600 pixels on the largest scale, and then upload. No problem.It does not help you to switch probes - The timebase would be the same.Probes that are not matched to your input impedance would over or under compensate = A rounded squarewave - Not a "longer"

author: timb
author_rank: Super Contributor
timestamp: December 06, 2015, 07:11:17 pm
content: Quote from: Applemac on December 06, 2015, 05:25:04 pmWhat? Yes it does. The iPad takes standard JPEG files. Try uploading to a site likewww.imgur.comand using the {img} tags.Also, make sure your probe is on the 10x setting. Watch the previously posted video about probe compensation.Finally, set the AC-GND-DC switch to GND and position the trace on the center graticule. Now, use the Trace Rotation control to make it as level as possible. Once that's done, don't touch it anymore.

author: Applemac
author_rank: Regular Contributor
timestamp: December 06, 2015, 07:41:53 pm
content: Dear all,Thanks with all the help its now after all your info producing a sharp square wave.