TBS1052C multiply problem

Our set of TBS1052C oscilloscopes exhibit a strange effect when multiplying two waveforms. The attached shows the multiplication of two sine waves (yellow and blue waveforms) with equal frequency, 2:1 amplitude and a small phase difference. The first screenshot (Waveform1.png) shows the expected  result from multiplication (red waveform) - a 2x frequency sinewave with DC offset. However, when changing the volts/per division of one channel, the second multiplied waveform becomes distorted (Waveform1.png). We have tried different oscilloscopes of the same model and they all exhibit the same problem. However, interestingly the version B doesn't have the problem. 

Hi Andrew,

I was able to replicate your issue, the solution I found was to go into the Math menu, go to Page 2 and lower the vertical scale until this didn't happen anymore.

Obviously, this is a bug so I've reported it, I'll let you know once I have an update.

Thanks Afonso - I'll try your suggested workaround.

Andrew

Hi Andrew,

I do not think we'll be able to get you a fix in 3 weeks, you'll have to use a workaround, sorry.

I am in contact with the engineering team but I don't have a timeline for a fix yet.

Afonso - I must say this is very poor service. We bought around 50 oscilloscopes from you that are less than 12-months old that have a serious, fundamental fault. I informed Tektronix of the problem over a month ago. How many users are out there that are using the multiply function without realising it is in error - the problem was obvious for the simple set up we have.

We renew our oscilloscopes on a 3-year basis - we won't be using Tektronix again.

Andrew