sorry, I couldn't resist... 🤣🤣🤣🤣
https://www.scientologie.fr/faq/sci.../what-is-the-emeter-and-how-does-it-work.html
I have seen your lab in your videos.
Nice place to work. Nice new meter, good job.
On my bench is a similar new Keysight 34461A DMM.
The newest gizmo is a Keysight E36312A power supply to bower bench projects
Keysight E36312A - 80W Triple Output Power Supply 6V/5A, (2) x 25V/1A, USB, LAN
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Chatgpt will undoubtedly adapt the definitions of 'crappy' measurements to the needs of the time.
Staring at the sun, one can detect both the leading and the trailing sundogs on the rims.
Staring at the sun, one can detect both the leading and the trailing sundogs on the rims.
Crappy probes = crappy measurements.
I got really lucky recently with purchase of a 7704A -- the fella threw in a dozen Tektronix and Phillips probes and almost all work perfectly.
I got really lucky recently with purchase of a 7704A -- the fella threw in a dozen Tektronix and Phillips probes and almost all work perfectly.
Looks like a great meter at a decent price. Still, out of my range. My HP3455A does just fine. For low resistance measurements I use an HP3478A and 4-wire probes. As a voltnut I'd really like a 7.5 or 8.5 digit meter, but that's not happening anytime soon. At a similar price as that meter, I keep looking at newer Siglent and other modern scopes, but haven't pulled the trigger. Anytime I get ready it seems like I need a root canal, car repair or some other thing.
With the discussion of electrometers in mind, probably the best reference on low level measurements is Keithleys Low Level Measurements Handbook:
https://download.tek.com/document/LowLevelHandbook_7Ed.pdf
Covers the ways to actually get meaningful measurements from extremely sensitive circuits and equipment.
https://download.tek.com/document/LowLevelHandbook_7Ed.pdf
Covers the ways to actually get meaningful measurements from extremely sensitive circuits and equipment.
Conrad-
I heartily agree with you on the usefulness of a 3455A or a 3456A. I have one of each on my rack and they will never be removed. Both have not been adjusted in years (18 for the 3455A and 15 for the 3456A) and are still well with original specifications. The only work that has been done to either is to replace the bulk filter capacitors for the power supply rails. I bring them in to work every year or so and check them against one of our 3458As or Fluke 5520A calibrators and they have effectively had no drift for the last 8 years that I have had them. Truly well built and impressive examples of HPs finest.
I heartily agree with you on the usefulness of a 3455A or a 3456A. I have one of each on my rack and they will never be removed. Both have not been adjusted in years (18 for the 3455A and 15 for the 3456A) and are still well with original specifications. The only work that has been done to either is to replace the bulk filter capacitors for the power supply rails. I bring them in to work every year or so and check them against one of our 3458As or Fluke 5520A calibrators and they have effectively had no drift for the last 8 years that I have had them. Truly well built and impressive examples of HPs finest.
@George - YW!
In very low level/precision measurements, as with RF, you quickly find that it gets expensive very quickly. The equipment itself is reasonable but the fiddly bits that make it actually work are very high. Often the cables, adapters, probes and such are many times the cost of the base equipment - and this is something that you truly do get what you pay for: those cheap Chinesium triaxial cables are pretty much useless when you really want to get down in the weeds with your measurements. And God help your wallet if you ever decide to get into measuring RF things over a few GHz or so - it is not unusual for a simple N to 2.92 adapter to cost $500 or more, and the cables can make that look cheap. Yes, you can find used accessories on ePay but there is generally a reason something that costs that much to replace is being sold rather than kept. The connectors have a limited number of attach/unattach cycles before they are out of tolerance, BTW, and very specific torque requirements for those connections.
Hal
In very low level/precision measurements, as with RF, you quickly find that it gets expensive very quickly. The equipment itself is reasonable but the fiddly bits that make it actually work are very high. Often the cables, adapters, probes and such are many times the cost of the base equipment - and this is something that you truly do get what you pay for: those cheap Chinesium triaxial cables are pretty much useless when you really want to get down in the weeds with your measurements. And God help your wallet if you ever decide to get into measuring RF things over a few GHz or so - it is not unusual for a simple N to 2.92 adapter to cost $500 or more, and the cables can make that look cheap. Yes, you can find used accessories on ePay but there is generally a reason something that costs that much to replace is being sold rather than kept. The connectors have a limited number of attach/unattach cycles before they are out of tolerance, BTW, and very specific torque requirements for those connections.
Hal
Hal
You are certainly right. RF and low level DC measurements are difficult to be executed properly.
What I object with the thread title and repeating pull-legging from Jan 🙂 is that a high resolution and wide range measuring instrument is not going to safeguard someone from making a “crappy measurement”. On the contrary, more digits and very low range capabilities of an instrument are going to fool someone that he is capable of doing a precise measurement.
e.g. I will accept as realistic a reported 3.211V measurement result done in a domestic environment but not a 3.2110000V one, even when done with the same 8.5 digit (hypothetical) instrument.
Again there are many factors affecting a measurement.
I am not expecting an amateur will do an uncertainty budget for each of his measurement procedures but I would expect from him to understand what his best measurement capabilities can be.
https://www.esscolab.com/uploads/files/measurement-guide.pdf
George
You are certainly right. RF and low level DC measurements are difficult to be executed properly.
What I object with the thread title and repeating pull-legging from Jan 🙂 is that a high resolution and wide range measuring instrument is not going to safeguard someone from making a “crappy measurement”. On the contrary, more digits and very low range capabilities of an instrument are going to fool someone that he is capable of doing a precise measurement.
e.g. I will accept as realistic a reported 3.211V measurement result done in a domestic environment but not a 3.2110000V one, even when done with the same 8.5 digit (hypothetical) instrument.
Again there are many factors affecting a measurement.
I am not expecting an amateur will do an uncertainty budget for each of his measurement procedures but I would expect from him to understand what his best measurement capabilities can be.
https://www.esscolab.com/uploads/files/measurement-guide.pdf
George
George-
I agree completely with that- it's very easy for even those of us who should know better to confuse resolution with accuracy. Just look at all those pretty digits 😵
Really, for 99% of what is usually needed, a good handheld Fluke will serve you better than a expensive bench meter. As you say, the key is understanding not only what you are measuring but why are you measuring it in the first place? What can affect the measurements? How much accuracy is needed? What matters in real world terms and what does not? For an audio related example there are many threads where something that causes 0.002% distortion is loudly denounced as being twice as bad as something that causes 0.001% - while technically true, in the real world it Just. Doesn't. Matter. That being said, there are things with which a 0.001% difference can make a significant impact - but not very many of them...
Hal
I agree completely with that- it's very easy for even those of us who should know better to confuse resolution with accuracy. Just look at all those pretty digits 😵
Really, for 99% of what is usually needed, a good handheld Fluke will serve you better than a expensive bench meter. As you say, the key is understanding not only what you are measuring but why are you measuring it in the first place? What can affect the measurements? How much accuracy is needed? What matters in real world terms and what does not? For an audio related example there are many threads where something that causes 0.002% distortion is loudly denounced as being twice as bad as something that causes 0.001% - while technically true, in the real world it Just. Doesn't. Matter. That being said, there are things with which a 0.001% difference can make a significant impact - but not very many of them...
Hal
One example: Victor's LDO - frequency change in time (2h) - measured directly by DMM6500 (no PC needed).
Makes one wonder what measurements and precision are necessary to afford such an instrument?
I can afford one but I am content with my HP 3478A's and some Fluke's etc. plus other functions. I have enough DMM's for what I need.
Remember there is a "need" and there is a "want".
I had the pleasure of working as a young tech in a Motorola Comm factory cal lab, it was a life long learning experience. What do I get to cal or fix today? Oh shoot it's the box of broken cables that need fixing. Some RF cables for special test stations, required to be TDR'd. There was a Wiltron TDR with a return loss bridge for that. At that time we used a Fluke 5101B calibrator. It wasn't very often we had to take the cover off to cal a DMM, analogs, VTVM's needed cal more frequently. My work bench at home today basically has the exact same test gear as my bench at Motorola, but I paid a fraction of what the stuff cost as new. You save enough in order to get a spare for parts since many parts are long obsolete. My HP 8656B is from the Motorola factory were I worked, I got it off ebay from a guy who worked in the EE lab and got it at the auction when they finally shut it down. Last cal sticker was from my old work friend that left Mot. & went to HP/Agilent. I might have had to lug the 8656B back to my bench one day to do the annual performance check/cal on it at one time🙂 Won't know for sure since I do not have the cal log for it. Glad I grabbed the many service manuals they they were going to through out in the garbage since they had so many of them. Fun times on the lab bench, got to go check a PS under test with my old test gear 🙂
I can afford one but I am content with my HP 3478A's and some Fluke's etc. plus other functions. I have enough DMM's for what I need.
Remember there is a "need" and there is a "want".
I had the pleasure of working as a young tech in a Motorola Comm factory cal lab, it was a life long learning experience. What do I get to cal or fix today? Oh shoot it's the box of broken cables that need fixing. Some RF cables for special test stations, required to be TDR'd. There was a Wiltron TDR with a return loss bridge for that. At that time we used a Fluke 5101B calibrator. It wasn't very often we had to take the cover off to cal a DMM, analogs, VTVM's needed cal more frequently. My work bench at home today basically has the exact same test gear as my bench at Motorola, but I paid a fraction of what the stuff cost as new. You save enough in order to get a spare for parts since many parts are long obsolete. My HP 8656B is from the Motorola factory were I worked, I got it off ebay from a guy who worked in the EE lab and got it at the auction when they finally shut it down. Last cal sticker was from my old work friend that left Mot. & went to HP/Agilent. I might have had to lug the 8656B back to my bench one day to do the annual performance check/cal on it at one time🙂 Won't know for sure since I do not have the cal log for it. Glad I grabbed the many service manuals they they were going to through out in the garbage since they had so many of them. Fun times on the lab bench, got to go check a PS under test with my old test gear 🙂
In reality, not very many unless you have been bitten by the volt nuttery bug. For me it is useful - and worth it - since a big part of my restorations are equipment that I need to adjust to specifications and the 7.5 digit capability of the DMM7510 fit the bill for me quite well being at least an order of magnitude greater than required most all of what I adjust. While a 3458A would be nice, I just don't need it - and it doesn't have integrated graphing. For the money I think the best choice for a mid-resolution bench DMM is one of Siglents SDM30x5 series - graphing and a very usable UI.
Hal
One of the old calibration tests was to use a new carbon-zinc cell, preferably "D" size and measure the open circuit voltage. VTVMs of the day had a red dot on the 1.5 VDC scale and in calibration the cell would have the pointer nicely split the dot.
Anyone who is not old enough to actually know the answer is welcome to test their favorite meter and see what voltage they read.
Anyone who is not old enough to actually know the answer is welcome to test their favorite meter and see what voltage they read.
Sorry, I only have a HP 400D AC VTVM, it was a parting gift when I left Motorola ... I still use the knife set however, but the 400D is for the museum
Does that equipment say in the performance test procedures a requirement for 7.5 digit capability or accuracy? If it does, then you have what's required, so it's justified that way, now it comes down to pay back, if its capital equipment, a bean counter issue 🙂 Sounds like Jan's op. is a one man show, so it comes down to how deep are your pockets. Cheers folks off for a drive in the country, leaves are changing already