Tools & Procedures for Calibrating Oscilloscopes - Page 1
Forum section: electronics / testgear

author: fmashockie
author_rank: Frequent Contributor
timestamp: December 23, 2023, 04:59:01 pm
content: Hey everyone! I am reaching out for suggestions for how to calibrate/performance check an oscilloscope. I recently purchased a non-working Tektronix 2230 (it has a ton of issues). The service manual for this scope provides a list of equipment you need to conduct performance checks and calibration. They list the Tektronix TM500 series with all its plug-ins (PG506 calibration generator, SG503 leveled-sine wave generator, TG501 time-mark generator, SG502 oscillator, PG501 pulse generator). For some of them, like the oscillator/sine-wave generator, I assume any old function/signal generator would work? But I'm not even sure what the others do! These plug-ins (and the TM500 chassis) are getting harder to find; and if you do find one, they can be expensive.It also seems the TM500 series is the go-to for older oscilloscope servicing as even the manual for my HP 54602 scope has some of these plug-ins listed as necessary equipment for calibration/servicing.My question is as follows: What alternative tools could I use to conduct performance/calibration adjustments of these scopes if I don't have the Tektronix TM500 series plug-ins at my disposal? If there is alternative equipment (ideally more accessible and potentially cheaper), where could I find procedures to utilize them appropriately?Thanks in advance!

author: bdunham7
author_rank: Super Contributor
timestamp: December 23, 2023, 05:17:25 pm
content: You can do everything you need for that scope with a good quality AWG that goes to 100MHz. You just have to deconstruct the manual a bit to determine exactly what input they are asking for when they specify a setup using those specific tools.

author: David Hess
author_rank: Super Contributor
timestamp: December 25, 2023, 01:28:32 am
content: The vertical calibration requires low frequency square waves with accurate amplitude, and can be done with a function generator or AWG, a good AC voltmeter, and some attenuators. The attenuators are needed to accurately get low valued square waves.Really vertical calibration only needs to be done on two ranges, with 2mV/V being one of them because there is a separate trim for that range. The calibration between the other ranges depends on fixed resistor networks, so only one trim is required for them.Horizontal calibration can be done with a frequency source up to maybe 10 MHz, however like 50 or 100 MHz is required to do the linearity and x10 calibration of the fastest sweep speed. The manual has the details.The hard part, at least as far as required equipment, is the high frequency transient response calibration. That requires a fast reference level pulse generator like the PG506 mentioned in the service manual. Common function generators, pulse generators, and AWGs are not up to meeting the speed and flatness requirements. Leo Bodnar hassomething suitable, or it is possible to make something with 74AC or 74LVC logic gates and careful construction.Using the recommended PG506 calibration generator and TG501 time mark generator makes the whole process much quicker.