开云体育

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of si_emi_01
Sent: Saturday, April 30, 2022 10:21 PM
To: [email protected]
Subject: Re: [TekScopes] 2465 Calibration

Some responses.

Do you have a lot of Overshoot or Undershoot on the waveforms you are supplying it? On the other scope, what is the Rise and Fall Time? If it is too fast, since the Impedance is High, it could cause reflections. It says the Rise/Fall time is less than 10ns.

You are likely been bit by a Signal Integrity issue. The Signal Generator edge is too fast. With an edge as fast as that is, it needs to be terminated into the cable Impedance. This isn't possible in your case because the Oscilloscope Calibration routine expects certain values to be met.

As a test you could use a 50 Ohm in-line Terminator, connect that to the Oscilloscope Input. Set the Generator for twice the Voltage level (only below 2V to protect your load and Generator), start the test and see if the problem goes away (as a test only). If it works it is likely caused by Undershoot or Undershoot. If not, the problem might be somewhere else in the Signal Chain.

You might try a real short cable too reducing the cable Propagation Time and hence the ringing that could occur.

If the Rise/Fall Time is programmable make it slower per the information I provided. It may use a current source for the output, which makes the following option possible. It would give you symmetrical edge rates. If they are not, the Rise Time or Fall Time may not be the same. I'm not sure how close you need to be to my values.

Another option is that the 1kHz Frequency is pretty slow - lots of settling time possible. You could slow the edge down without affecting the Square Wave output level. I have provided information below that will help you get near the Rise/Fall Times my PG506 produces.

If you are able to slow it down, it might fix it.



I remeasured my two PG506s. The numbers are almost identical, so I will give the numbers just one:

Amplitude Output (STD and High) Connector into my Tektronix 5104 Oscilloscope
-------------------------------------------------------------------------------------------------------------
Termination - 1 MegOhm Internally Terminated input Frequency - 1.024kHz Amplitude - Follows the Amplitude Knob setting Rise Time - 12.86us (microseconds) Fall Time - 12.56 us (microseconds)


Trigger Output Connector into my Tektronix 5104 Oscilloscope
------------------------------------------------------------------------------------
Termination - 50 Ohm Internally Terminated input Frequency - Follows the Period knob setting Amplitude - Didn't record it - Crap!
Rise Time - 8.66ns (nanoseconds)
Fall Time - 4.86ns (nanoseconds)


Fast Rise (+) Going Output Connector into 50 Ohm Internally Terminated input of Tektronix 5104 Oscilloscope
-----------------------------------------------------------------------------------------------------------------------------------
Termination - 50 Ohm Internally Terminated input Frequency - Follows the Period knob setting Amplitude - 300mV Rise Time - 504.0ps (picoseconds) Fall Time - 664.0ps (picoseconds)


Fast Rise (-) Going Output Connector into 50 Ohm Internally Terminated input of Tektronix 5104 Oscilloscope
-----------------------------------------------------------------------------------------------------------------------------------
Termination - 50 Ohm Internally Terminated input Frequency - Follows the Period knob setting Amplitude - 300mV Rise Time - 504.0ps (picoseconds) Fall Time - 504.0ps (picoseconds)


Ross

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of jimbert4 via groups.io
Sent: Saturday, April 30, 2022 4:44 PM
To: [email protected]
Subject: Re: [TekScopes] 2465 Calibration

That makes sense. Oh, and I discovered that in Cal 02, vertical calibration, the 2465 is NOT put into 50 Ohm DC input mode. It is in high impedance mode. So my voltages are not being divided by 2. So now I don't know what the heck is causing the Limit errors. Sigh. Could it be that my square waves low side is not exactly at 0V? It's hard to get it exactly right on my PSG9080 signal generator. I'm using another scope to set the high and low levels as close as I can, but they interact and I can rarely get them both exactly right. Close though, within 10s of mV.