How many ever worked in a Metrology lab? How many on here ever did mission critical work, where it was damn near impossible to get the equipment back in a reasonable time, to correct any errors? Our equipment ended up in space, or places like Antarctica where it could take a year to return and repair a piece of equipment due to the transportation issues.
toggle quoted messageShow quoted text
I agree that the old stored values are not all correct, but they are better than nothing for a casual user who can't do a full calibration.
If they need better results, then it should be sent out for a proper calibration, but after doing the usual PM.
One job while in the US Army was doing PM on hundreds of video monitors for the Helicopter Flight School at Carin Airfield, and for the Air Traffic Control Towers. Rather than wait for them to fail, they were rotated out to the shop every six months and examined for possible problems. Even back in the early '70s, we saw a lot of bad electrolytics in the equipment. It was no fun carrying those 25" steel cased monitors up the narrow circular stairs to the control room.
Still it was better than the higher risk of losing more than one monitor when our section's shop was closed. The pilot's classrooms used regular TVs, so they were someone else's problem, but there were multiple monitors scattered all around the ready rooms and towers for two channels of weather data. If our system went down, they closed the school until it was back up and running.
Michael A. Terrell
From: Chuck Harris <cfharris@...>
Sent: Oct 15, 2018 10:08 AM
Subject: Re: [TekScopes] Tek 2467B
How many people would simply slap a calibration sticker
on a scope and charge for the calibration?
Using yourself as the minimum standard by which all
technicians, and calibration shops, operate is rather
That most of theses scopes haven't been in the hands
of cal lab for decades makes it even more likely that
the calibration constants are not worthy of saving.
Sure, some of the values may be right on, but which
are those? Which are wrong? You really can't tell
until you calibrate the scope.
How many of the guys on this group have replaced a
vertical attenuator, vertical hybrid, trigger hybrid,
a couple of 10K precision resistors on an A5 board,
a tripler, or perhaps even an entire EHV power supply
board and never once thought about doing a calibration?
Show of hands?
Michael A. Terrell wrote:
How many people would calibrate a scope, before verifying the scope didn't have bad caps? The S/H cap would be the least likely to fail, compared to the average lifetime of the electrolytics. Also, most of the scopes ending up in private hands haven't been in a cal lab for years or even decades so recapping the electrolytics would return it to the condition it should have been in at the last calibration. At least, anything I repaired would have been done this way.
Leakage around the S/H circuit's capacitor could be affected by contamination on the circuit board, as well. A good cleaning should always be part of testing and calibrating very high impedance circuits, as you well know. :)
I too, have worked in electronics for decades. Over five of them including at the factory on systems that were only allowed a 1.5 mV error in a system with a 0 to 5V output in a complex AGC circuit comprised of 14 Op-Amps. One of these boards was part of a kU band communications system for the International Space Station.