Look at any of their scope front panels before the 24xx series. The timebase has units of mS.
Quote from: tggzzz on Yesterday at 06:47:19 PMLook at any of their scope front panels before the 24xx series. The timebase has units of mS.
Well, let's see. I have a 2232 and 2247A in front of me. And I have a 2230, 465, various 7000, and a 547 in the other room. All use lowercase "s" except for the 547 which uses all lowercase "sec" on their front panels and except for the 7000 readouts, they also all use lowercase "s" but the later later readouts had better precision.
So do you have a specific example?
I'm going to keep using mhos just to spite SI; and because it is much more mnemonic and avoids confusion with seconds no matter how marked.
Now that really annoys me: you are right and I am wrong.
Where on earth did I get that misapprehension - which has lodged in my brain over the decades? I must be channelling Aristotle, who maintained women had fewer teeth than men, but never opened either of his wifes' mouth to count them!
Now that really annoys me: you are right and I am wrong.
It happens to me also. Forget about it.
QuoteWhere on earth did I get that misapprehension - which has lodged in my brain over the decades? I must be channelling Aristotle, who maintained women had fewer teeth than men, but never opened either of his wifes' mouth to count them!
I had examples at hand to look at first hand so did not have to rely on memory. For all I know, the other 465 and 22xx series models use an uppercase "S".
Unfortunately, all this nomenclature fussiness has distracted from any real technical discussion of the; Impedance changing amplifier, Delta-Z Buffer or thing-a-ma-jig in question. I do find this item quite useful. It can be put into a spectrum analyzer - tracking gen loop to allow for characterization of scope probes or other 1Meg output impedance items. It is also useful for extending the cable on such items in certain test situations.
Impedance converters or buffers are very handy. Another place they can be used is to drive a 50 ohm frequency counter with a standard high impedance passive prove. I have seen them used for low frequency network analysis.
With an adapter that includes enough shunt capacitance, an active probe can be used as an impedance converter.
When I designed this buffer, I set up the input to look like a typical scope input ie 1M/18pf specifically so scope probes would work correctly. That would also apply to your active probe I would guess in most cases. Trim adjustment of the probe would probably be advisable for best performance.
I built another version of this type of Impedance Matching Amplifier based on a different op-amp. This version, while more complicated, uses a lower cost chip ($5 vs $15) and has a few other advantages and some disadvantages:
Advantages:
1) It's gain is 0dB rather than -6dB nominal.
2) It has a slighter higher -3dB point and the roll off is slower, resulting in usability over a greater range.
3) The 2nd Harmonic at 100MHz is down about -50dB rather than -40dB for the previous circuit.
4) Op-Amp is cheaper
5) Possible performance improvement through circuit tweaks.
6) Increased gain possible.
Disadvantages:
1) Circuit is more complicated and requires +/-5 volt regulators.
2) Previous circuit would tolerate higher input voltages as it used 9V supplies rather than 5V.
3) Harmonic data shows some spurious signals between the 2nd and 3rd Harmonic, largest of which is -50dB down from fundamental.
This version of the circuit board had an error on the IC pinout so some bodges were required. Also a pot was bodged in to adjust the gain to as close to 1:1 as possible over the frequency range of interest.
I believe that further improvement can be obtained from this op-amp, after another run of PCBs to correct errors and add a few elements for flexibility we will try again.
Yet another version of this circuit using the VCA821 suggested amplifier is in progress but I've yet to receive the PCBs.
Quote from: tggzzz on Yesterday at 06:47:19 PMLook at any of their scope front panels before the 24xx series. The timebase has units of mS.
Well, let's see. I have a 2232 and 2247A in front of me. And I have a 2230, 465, various 7000, and a 547 in the other room. All use lowercase "s" except for the 547 which uses all lowercase "sec" on their front panels and except for the 7000 readouts, they also all use lowercase "s" but the later later readouts had better precision.
Quote from: tggzzz on Yesterday at 06:47:19 PMLook at any of their scope front panels before the 24xx series. The timebase has units of mS.
Well, let's see. I have a 2232 and 2247A in front of me. And I have a 2230, 465, various 7000, and a 547 in the other room. All use lowercase "s" except for the 547 which uses all lowercase "sec" on their front panels and except for the 7000 readouts, they also all use lowercase "s" but the later later readouts had better precision.
Meh? Not mine! Indeed, not in any picture I could find, they all have SEC in upper case. And I leafed through Stan Griffith's book and looked at tons of old Tek stuff.
I also put slashes through my zeros and dashes through my 7s and Zs.
I also write my dates in DDMMMYYYY format, thus: 24May2018. This completely eliminates the possibility of confusion between the day and month, since depending upon the writer and reader the two formats MM/DD/YYYY and DD/MM/YYYY are not definitive for days <= 12. The four digit year might seem unnecessary, except to those of us who write software and/or lived through the whole Y2K thing.
I write out my dates in some form of numeric YYYYMMDD to match what I type into computers so they may be easily sorted.
And I swap the control and caps-lock keys on my keyboards so that the control key is next to the A key where God intended it. This has occasionally resulted in hilarity when someone tries to use my computer.
I just purchased a new ThinkPad X270. They reversed the Ctrl and Fn keys (Fn is to the outside on the extreme left).
Your first Thinkpad, I reckon? They have been doing this since 1992.... (Which still doesn't make it a good idea, in my book...)
Yes, my first ThinkPad. I have zero brand loyalty, I just start with a list of required specs. I build my own home machines but you sort of have to buy laptops.So I start with specs and winnow the field.
EDIT: I just read the comments in that link you provided. Here's one that sums it up: "My business partner standardized our laptops on Lenovo. Let me tell you, I remedied that in less than a year. Why, and what would make me switch back to these otherwise great machines? This button arrangement. Love the explanation, and I wish the others had all followed suit, but they didn't. We've swapped the buttons in BIOS but it causes unfamiliar users tons of pain as they keep raising issues thinking the button is broken because they're pressing the wrong one now."
Impedance converters or buffers are very handy. Another place they can be used is to drive a 50 ohm frequency counter with a standard high impedance passive prove. I have seen them used for low frequency network analysis.
Impedance converters or buffers are very handy. Another place they can be used is to drive a 50 ohm frequency counter with a standard high impedance passive prove. I have seen them used for low frequency network analysis.why dont just build an active probe (Hi-Z in 50 ohm out) with selectable 1x 1/10x input? less one Hi-Z probe to take care about. cost should be less than $100 alltogether.
Why couldn't Lenovo at least make the two keycaps the same size, so you can physically swap them?
Regarding quotes on that web page, my favorite one is from the main author of that Q&A: "Every other notebook personal computer manufacturer that I know of has the Fn and Ctrl key positions swapped."
Impedance converters or buffers are very handy. Another place they can be used is to drive a 50 ohm frequency counter with a standard high impedance passive prove. I have seen them used for low frequency network analysis.why dont just build an active probe (Hi-Z in 50 ohm out) with selectable 1x 1/10x input? less one Hi-Z probe to take care about. cost should be less than $100 alltogether.
I just found this thread. I have a Marconi 2374 high-Z probe (specified bandwidth 200 MHz) for my Marconi 2380/2382 400 MHz spectrum analyzer (50 ohm input).
I tested the THD of the probe at 500 kHz (half the maximum frequency of my Wavetek 98 DDSvgenerator, which has low THD at its 50 ohm output.
Without probe: 50 ohm output to 50 ohm input. THD = 0.12% for the naked generator (-63 dB 2nd, -61 dB 3rd, and -70 dB 4th) at 0 dBm/50 ohms = 0.22 V rms.
With probe: 50 ohm output to 50 ohm terminator to probe to 50 ohm input. THD = 1.5% (-37 dB 2nd, -46 dB 3rd, and <-72 dB 4th) at same generator level.
I quote these values as what can be accomplished with a simple circuit with discrete devices; obviously, the probe distortion is much worse than the generator's THD.
The probe comes with a set of input attenuators, which I haven't tested.