RF equipment calibration - Page 1
Forum section: electronics / testgear

author: LeoUCDavis
author_rank: Contributor
timestamp: December 24, 2015, 12:26:41 am
content: Hi allI have always wondered whether it's possible to calibration RF equipment by oneself. I understand that you may need a set of calibrated references. What would be a minimum set of such references?

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: December 24, 2015, 01:40:14 am
content: What equipment are you "trying" to calibrate? The awsnser is always is technically yes but! There is also the question of traceability.Are we talking about just using a calibration kit on a network analyzer, know RF power and frequency standard to make for a smaller confidence interval for the measurement. Or are we talking about a full factory calibration of an instrument.Some good things to have no matter what is a set of opens, shorts, and matched loads to system impedance over the frequency of operation. A good power meter is always helpful. Some very low loss cables are a must for any high-end RF stuff. If doing free space stuff(probably not) standard gain horns are a must.Some more information about what you are thinking of calibrating would be helpful. There are a lot of different instruments that fall under the category of RF and all do different things and have there own calibration methods and equipment.

author: LeoUCDavis
author_rank: Contributor
timestamp: December 24, 2015, 03:08:01 am
content: Yes I should be more specific. I am indeed thinking of calibration DMMs, oscilloscopes, power meters, spectrum analyzers for "for a smaller confidence interval for the measurement". Instead of sending the instrument to a calibration lab every year, I wonder if it would make more economic sense to invest in calibration tools.I do have the typical RF cal-kits for VNA calibration.

author: Vgkid
author_rank: Super Contributor
timestamp: December 24, 2015, 03:40:58 am
content: Since you work for a university, you would be buying new gear. Will they allow used gear from reputable dealers?

author: LeoUCDavis
author_rank: Contributor
timestamp: December 24, 2015, 03:49:16 am
content: Quote from: Vgkid on December 24, 2015, 03:40:58 amCertainly. Even buying from eBay is allowed.

author: Vgkid
author_rank: Super Contributor
timestamp: December 24, 2015, 04:25:53 am
content: Quote from: LeoUCDavis on December 24, 2015, 03:49:16 amGood, that gives you a million more chances to buy good gear.

author: LeoUCDavis
author_rank: Contributor
timestamp: December 24, 2015, 05:55:22 am
content: Quote from: Vgkid on December 24, 2015, 04:25:53 amThat's what I discovered recently. However, many second-hand good stuff on eBay are not calibrated... hence the question

author: Vgkid
author_rank: Super Contributor
timestamp: December 24, 2015, 08:58:56 am
content: A few vendors will actually calibrate the gear. Otherwise buy the gear, test it, and send it out for calibration. Some equiptment (rubidiums.gpsdo's) are actually self calibrating*. Sothey either work, or not.*Rubidiums do drift, but that is not much to worry about. Just check it against the gpsdo...What gear do you have at hand?

author: LeoUCDavis
author_rank: Contributor
timestamp: December 24, 2015, 05:47:34 pm
content: Quote from: Vgkid on December 24, 2015, 08:58:56 amVNAs, SAs, oscilloscopes, signal generator, DMMs, power supplies are mostly what I have. If you have a Rubidium, a voltage reference, and a power meter that are traceable, would you say that you could use them to keep most other equipment in good traceability?

author: KJDS
author_rank: Super Contributor
timestamp: December 24, 2015, 06:08:18 pm
content: If you've got a calibrated power meter then you can check the output level from a signal generator. Then put the same sig-gen into your spec ana and see what level it reads. Check harmonic levels too, as the power meter will read both. If you've got an accurate frequency reference then you can use that to lock the sig-gen too then check the spec ana.Make sure you understand RF VSWR errors. If a power meter reads a clean signal at 0dBm and so does your spec ana, it's tempting to think everything is rosy, however if your power meter is a little capacitive and your spec ana a little inductive, and thanks to the source match then things are working against you then errors can soon add up.

author: LeoUCDavis
author_rank: Contributor
timestamp: December 24, 2015, 10:41:54 pm
content: Quote from: KJDS on December 24, 2015, 06:08:18 pmThanks for the info. Sounds like I need the following:calibrated frequency referencecalibrated voltage referencecalibrated power meterAny others I should have?

author: nidlaX
author_rank: Frequent Contributor
timestamp: December 24, 2015, 11:14:26 pm
content: Quote from: LeoUCDavis on December 24, 2015, 10:41:54 pmTo completely calibrate some DMMs, you'll need a DC voltage calibrator, an AC voltage calibrator, a resistance calibrator, and a current calibrator. Having a fixed output DC voltage reference is not enough to calibrate the DC voltage ranges on most multimeters because each range, from mVs to 100s of Vs, will require a corresponding calibration voltage. You can often find calibration instruments with a variety of functionality combined into one unit. A good example would be the Wavetek/Datron line of calibrators, but unfortunately they typically cost many thousands of dollars to purchase second hand.An HP 3245A might be useful for voltage and current calibration purposes.

author: LeoUCDavis
author_rank: Contributor
timestamp: December 24, 2015, 11:34:56 pm
content: Quote from: nidlaX on December 24, 2015, 11:14:26 pmI see. This is quite complicated. Thanks for the information.

author: acbern
author_rank: Frequent Contributor
timestamp: December 24, 2015, 11:38:04 pm
content: in my opinion, what I would recommend, as per your request if I understand correctly, and for even pretty serious use already, is the following:- 10V DC reference and a self cal voltage divider (720A/752A): covers all DC voltages- voltage sources (AC/DC), a fluke 5100 will do, it is just your transfer standard, not too precise- a RF source- a 3458A: together with thermal converter allows precise DC/AC measurements and current measurements together with your voltage sources- resistance standards (see above), can be DIY Vishay hermetic- a broad band power sensor (e.g. RS NRP, some go down to DC): RF AC- thermal converter, preferably with AC decade transformer DT72: LF AC transfer, for validation of LF AC- rubidium standard: frequencyyou can get the above for <10k on ebay I would think. Price also depends on your accuracy demands. E.g. if you do not need high accuracy LF AC measurements, no thermal converter/AC divider needed, just use the 3458A in AC SYNC mode.You need to develop a plan on how you start from thes standards to cover all ranges, and establish an error propagation analysis across the ranges (e.g., you have 10V standard, how accurate is your 1kV measurement). Some of the above is maybe simplified, your plan needs to establish all the details. You can save money, but it is an effort.Actually all I have calibrated externally as standards is a NRP RF sensor, a 10V DC source, a 10V thermal converter, a 10k ohms standard. The rubidium standard I calibrate using a GPS disciplined 10MHz receiver. All the rest I derive from these.Cal costs me less than 1k per year for all, with pretty low uncertainties. Some need cal only every three years per manufacturer if you use them seldom (as cal, and not as working standrads), such as the NRP RF sensor.Then I use auxiliarry devices: DC dividers (self cal), ESI SR series resistance transfer devices, DT72 (no cal), AC transfer meter and other gear such as 3458A, RF counter, RF gen, power splitter, resistance decade standards....That allows me to cal instruments with traceability that cover these ranges: DC 1mV-1kV, LF AC 10mV to 1kV, DC/AC Current 10uA - 10A, RF level and frequency (typically 10MHz-40GHz) , 0.1 ohm to 100MOhm.

author: G0HZU
author_rank: Super Contributor
timestamp: December 24, 2015, 11:42:16 pm
content: QuoteI have never sent any of my RF gear out for calibration because I think it adds little value and the downsides outweigh the upsides. Obviously, it would be different if I were running a business because I'd have to keep customers happy and so I'd have to pay for calibration.But sat here at home I wouldn't allow my RF test gear to go anywhere near a UK calibration house even if they offered me a complete door to door calibration service for free.I think it is far better to set up a few basic cross checks once you have several decent items of test gear.I also use a set of precision attenuators that step in 1dB steps and these work into the GHz region with very low VSWR. These help cross check various items of test gear.Although I have a newer power meter these days, my old HP431C with 478A thermistor head hasn't been formally calibrated since I rescued it from the company skip >20 years ago. But because it runs a closed loop system it has stayed in agreement with other power meters at 0dBm at 50MHz to well within 0.1dB in all this time. I use it as a cross check standard against the 50MHz power reference in my modern power meter and also against the various precision power references in my HP or Advantest spectrum analysers.In a well controlled 50R test environment the crosschecking performance of all of these is boringly reliable year after year assuming one isn't into chasing down beyond about 0.025dBI don't really see the need for a GPS or Rb frequency standard for home use. These would just be time wasting distractions that add no realistic value IMO. But they are cheap to buy nowadays so anyone can get one if they need this degree of accuracy.I do have a few cheapo low voltage reference chips here that cover up to 10V but I can safely say that these have added ZERO value to anything I have ever done here. I haven't adjusted any of my equipment because of them in many years. I don't think I've adjusted any of my DMMs (even the cheap ones) since the 1990s and I think they are as useful today as they were when I last adjusted them.

author: G0HZU
author_rank: Super Contributor
timestamp: December 24, 2015, 11:55:47 pm
content: QuoteAgreed. Understanding and managing mismatch uncertainty is far more important (and usually far more significant) when making many types of RF measurement.

author: LeoUCDavis
author_rank: Contributor
timestamp: December 25, 2015, 01:07:02 am
content: Quote from: G0HZU on December 24, 2015, 11:42:16 pmThanks for the advise. What do you use the step attenuators for?

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2015, 02:22:45 am
content: The step attenuators are useful for checking the linearity of the power meter across a wide range. For this to be valid the attenuators need to be very accurate and repeatable and also the VSWR needs to be very low.I can also use them to check the accuracy of the logamp stages in a spectrum analyser or the range accuracy of my old Racal 9300 true rms voltmeter down to a few microvolts.I also check the accuracy of the attenuator itself using DC tests, low frequency AC tests using a DMM and also tests using a VNA or a signal analyser that uses a fairly accurate digital IF.Here's an old copy of a dc and LF cal check on one of the step attenuators plus some cross checks at 50MHz and 1GHz using a power meter and a VNA. You can see that this attenuator is designed to have very accurate 1dB and 10dB increments making it a useful device. It's rated to 2GHz although the accuracy will obviously degrade a bit as the frequency goes up.This level of performance is easily good enough for me but obviously, this attenuator isn't formally calibrated. I'm due to recheck all this stuff again soon and I also have a new VNA to check.

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2015, 02:33:12 am
content: Here's an old comparison plot of my two power meters against one of my sig gens. This Agilent ESGD model sig gen is known for having a very flat response as you can see in the official plot below where several sig gens are measured for flatness in the same plot:In the other plot you can see my attempt to check its performance up to 4GHz using my two power meters. Again, none of this is traceable although the sig gen did come with a nearly fresh 2 year cal certificate when I bought it.The flatness graph was done automatically using GPIB and I included the cal factor vs frequency for the Anritsu power meter including interpolation between cal points. This meter and its sensor still seems fine to meThe HP431C uses a 478A power sensor and the input return loss of these sensors isn't that great above 2GHz so you can see some mismatch uncertainty ripple in the plot for the HP431C. But both plots are easily good enough for my needs anyway

author: LeoUCDavis
author_rank: Contributor
timestamp: December 25, 2015, 02:42:41 am
content: Quote from: G0HZU on December 25, 2015, 02:22:45 amGreat information. Thanks. I assume that this is an old HP unit?

author: acbern
author_rank: Frequent Contributor
timestamp: December 25, 2015, 09:40:37 am
content: The problem with all this described above is, sure, it gives you some indications, but without known accuracy limits, its just guesswork, and misses the point of the question. For hobbyist work, sure, it's perfectly fine.In a university or for professional work, you need to know the error budget, no way arround traceable calibrations.

author: KJDS
author_rank: Super Contributor
timestamp: December 25, 2015, 10:09:37 am
content: Quote from: acbern on December 25, 2015, 09:40:37 amIt's just a case of how far to take it. As I suggested earlier, if your power meter is accurate, and you have a VNA to check a set of attenuators then there is a great deal you can do yourself and still have things traceable. Sure there's more work to do to ensure that you know the error budget, but all a cal house will do to check the amplitude accuracy of a sig-gen is to run it into a power meter.

author: PA4TIM
author_rank: Super Contributor
timestamp: December 25, 2015, 10:37:47 am
content: Quote from: LeoUCDavis on December 24, 2015, 12:26:41 amThen you still have a problem, the standards need calibration too. And that is a lot more expensive. And to proper do a calibration you need to do that under the right conditions (temp etc)By the way, calibration is not adjusting

author: G0HZU
author_rank: Super Contributor
timestamp: December 25, 2015, 02:23:02 pm
content: Quote from: acbern on December 25, 2015, 09:40:37 amEven if you send the test gear off for calibration every year (or two years or four years) you can't escape from the fact that you are left hoping or guessing that the equipment will be 'calibrated'. You are hoping that it is accurate over time and temperature and operator usage, hoping or guessing that no one has knocked or abused it.Also, the calibration won't check for every possible frequency and level or mode you use in the equipment and usually the calibration just amounts to a check that the equipment is within its design limits. These limits can be quite wide.There is no perfect answer to this. In my opinion (based on having worked in RF labs all my working life) you have to rely on the design integrity of the test gear (i.e. choose your test gear manufacturer/model wisely) because this is where the true value lies. Having access to traceable calibration standards every year really doesn't add that much value to RF test gear, especially if you are working up at UHF or microwave frequencies. The real quality comes from the test gear itself and also the ability to use it and understand its limitations wrt what contributes to (or aggravates) its overall measurement uncertainty.There are basic checks that can be done to boost the confidence of measurements and a lot depends on what your application is. If you are designing calibration test gear for calibration purposes then this would be an extreme case where you would have to work very closely with a standards agency. But for most general purpose RF work this wouldn't be necessary

author: acbern
author_rank: Frequent Contributor
timestamp: December 26, 2015, 01:08:16 am
content: Sure, even a cal only gives you 95% (k=2) confidence. But that is accepted. You can also go to 99%, if need be, some vendors support this. Also, serious suppliers specify the max drift rates over a certain time once an item has been calibrated. These need to be part of the equation too.Anybody shipping an electrical product with specified behaviour needs to use cal'ed equipment in its production tests. ISO demands it. Same if you work in a universtiy and do research you wish to publish, you have to know your traceable error budget. This includes proper workmanship and related error sources.Just metrology / QA basics, no big news.

author: G0HZU
author_rank: Super Contributor
timestamp: December 26, 2015, 01:29:08 pm
content: But this thread isn't about shipping electrical products or ISO. The OP hasn't specified any requirements. I interpret this as a question as to whether it's possible to maintain reasonable calibration of test gear over longer intervals than one year by doing basic checks in a lab.There's no mention of wanting to ship products or conform to any regulations. Just a means to boost confidence of a given measurement beyond a 1 year calibration.FWIW, when I see a sig gen at work with maybe 6 months left on its annual calibration I see an instrument that passed a health check six months ago and it also means I can use it for certain applications without violating any company rules/procedures for another 6 months. That's all it means to me. It doesn't tell me how flat the sig gen response is over frequency or 'prove' how accurate it is when set to 0dBm or -120dBm at various frequencies.QuoteGoing off topic a bit here (and maybe I'm being pedantic but...) you don't 'have' to use traceable test gear to do valid research work in RF. Accuracy and innovation aren't tied together.

author: LeoUCDavis
author_rank: Contributor
timestamp: December 30, 2015, 08:06:21 pm
content: Quote from: G0HZU on December 26, 2015, 01:29:08 pmThat's exactly what I meant.QuoteYes indeed, but at some point, you always need an accurate measurement to show that your work is valid.

author: G0HZU
author_rank: Super Contributor
timestamp: December 30, 2015, 09:53:59 pm
content: QuoteI don't agreeSome things don't even need test gear or physical tests. Go back to the 1960s and look at a few classic patents. Some things just needed basic/classic theory and nothing else. eg the classic Sontheimer range of directional couplers. Even a student can explain how these work using a pen and paper based on theory dating back to the days of Faraday with no need to build anything let alone the need for traceable calibrations of any test gear.

author: G0HZU
author_rank: Super Contributor
timestamp: December 30, 2015, 10:14:52 pm
content: QuoteMaybe it would be best to describe this without using the word 'calibration' because this word is open to interpretation.For checking RF power here at home I have two RF power meters and three power heads covering up to many GHz. I can also use a packaged Agilent detector diode to check for flatness up to several GHz although these diodes are of limited use for making absolute measurements as they are temperature sensitive. However the detector flatness and input VSWR is extremely good (as in pretty awesome) from 100MHz up to 5GHz. It does prove useful when cross checking against my various power heads for flatness across a few GHz. I use one of the diodes in the range below (HP 8473C)http://cp.literature.agilent.com/litweb/pdf/5952-8299.pdfOne of my power meters is the classic HP431C with HP 478A thermistor sensor. This runs in closed loop and when used where the input VSWR is very low you can use DC substitution to improve accuracy although I have never bothered to go this far with it. I use this meter as a reference because it stays consistent year after year (for maybe 20 years so far). Note that I use it with a DMM connected to the rear DMM port rather than look at the analogue dial at the front.Unlike modern (open loop) thermocouple meters it doesn't need a 50MHz 0dBm onboard reference to self calibrate. So it doesn't have one fitted. The 478A sensor dates back 50 years or so and is often used to calibrate modern power meters because it is so simple and accurate. You can still buy one new from Keysight for about $4000 and the most accurate power meter made by Keysight uses a 478A based thermistor sensorI also have precision power references built into some of my spectrum analysers and these are very consistent year after year when cross checked. So I have references at -20dBm, -10dBm and 0dBm. I also have a way of homebrewing a reference at HF and VHF that is based on simple tests and theory. But I'm not really that interested in chasing down beyond a few percent accuracy. So the cross checking results I get year on year are much better than I think I needIn my experience, the ability to make fairly accurate relative measurements is also very important and I find that cross checking several instruments with precision attenuators is one way to boost confidence.But I'd probably better repeat that none of the stuff I do above is 'traceable' to any calibration house or standard. It just meets my needs for achieving high confidence in the measurements I make

author: G0HZU
author_rank: Super Contributor
timestamp: December 30, 2015, 10:48:42 pm
content: If anyone is interested in reading more about the old 478A sensor it's worth googlingdc substitution 478A NISThttp://cp.literature.agilent.com/litweb/pdf/5990-9078EN.pdfQuoteProvided you use a test frequency where the sensor VSWR is very good (eg 100MHz to 1GHz?) you can measure RF power with fairly high confidence using DC substitution. Of course the sensor could go faulty or be damaged but you could always buy several of themMine has been amazingly consistent for over 20 years.The standard 478A sensor is rated from 10MHz to 10GHz but the input VSWR is quite poor at the extremes of this range. They make a special version for very accurate use at 50MHz that has low VSWR at 50MHz.The important (elegant) thing is that the RF power fed into into the sensor is the same as the DC power you input to balance the sensor. So you can effectively use a DMM on the DC range to measure RF power very accurately instead of the HP431 or HP432 meter's internal metering. So there is no need to have any 50MHz or 100MHz 0dBm reference built into the meter

author: G0HZU
author_rank: Super Contributor
timestamp: December 31, 2015, 11:28:22 am
content: Here's an image of my little HP8473C detector diode.This device has a very flat frequency response although it isn't very accurate in absolute terms over temperature. So I use it for cross checking the flatness of various items of test gear. You also have to be wary of uncertainty caused by harmonic distortion terms in the signal under test if you use the detector up towards the top end (linear) part of its range.This one has an input return loss of better than 30dB right up to 5GHz and it gives best performance across 100MHz to 5GHz.

author: LeoUCDavis
author_rank: Contributor
timestamp: January 01, 2016, 12:08:26 am
content: Quote from: G0HZU on December 30, 2015, 09:53:59 pmI agree, but such elegant innovations don't come by everyday and you'd still have to keep the more mundane work going.

author: LeoUCDavis
author_rank: Contributor
timestamp: January 01, 2016, 12:30:47 am
content: Quote from: G0HZU on December 30, 2015, 10:48:42 pmThanks G0HZU for the writing on power measurement. I can see that the 478A is fairly inexpensive on eBay and I'm interested in getting one to play with. How would you ensure that the reading from a second hand sensor is reasonably accurate? Do you have to compare/adjust it with a "traceable" standard?

author: G0HZU
author_rank: Super Contributor
timestamp: January 01, 2016, 12:58:53 am
content: Because these sensors are so old and so easy to damage you may find it difficult to get a working one. From what I have heard they (usually) either work or they are obviously toasted. I would expect to see lots of dead ones on ebay. You also have to get a compatible power meter to go with it and I would recommend the classic HP432A from the 1970s. Don't worry about the old school analogue dial it has. You can use a DMM on the recorder output at the back and this is going to be good enough for most users. I don't like the 432B with the dated and basic digital display and would always go for the 432A.I did a quick return loss measurement of my 478A sensor using my VNA up to 1GHz. The plot below does say C? for cal but this is because I turned down the sweep speed after I calibrated and I experimented with different power drive levels after the calibration to see if it affected things. But the RL plot didn't alter. I'm too lazy to recal the VNA for the purpose of the plotNote that this VNA actually has a year left of a 2 year Keysight calibration so this is one of only a few items of test gear I have with current calibration stickers. I didn't pay for the cal, it was an existing cal on the VNA and the Ecal kit.But check out the return loss of this fabulous old power sensor...Even at 50MHz this one is at 29dB return loss which is easily OK for my needs in terms of uncertainty when used with a decent 50MHz source with good VSWR. The HP478A and the old HP432A power meter from the 1970s are one of the most impressive pieces of RF engineering I've seen because of the simplicity and the accuracy they offerI think I have a little nugget of gold here with mine and it just keeps on working every year returning consistent performance and it is my gold standard for power because of the simple/elegant way it worksBut I don't use it for general measurements because it is quite clunky and slow to zero and set up for every measurement and I'm nervous I might damage it. The overload/damage level is marked as being only 30mW. These things are fragile!There are some tests you can do to test a sensor on its own (without a power meter) and I'll see if I can find the info.

author: G0HZU
author_rank: Super Contributor
timestamp: January 01, 2016, 01:15:35 am
content: QuoteI guess only you know what you would accept as accurate. I just want consistency and for the first few years I owned this meter I used to bring it into work to check against the 0dBm reference used in the modern calibrated power meters at work. But it was boringly repeatable and I don't bother any more.I suppose the correct way to check it would be via dc substitution using an HP432A and a fairly decent DMM because this would exploit the true qualities of this sensor without worrying about how well adjusted the HP432A is in terms of the dial accuracy or its recorder output accuracy. But I'm much too lazy to bother to do this with my meter even though it has connections at the back marked up for operation using DC calibration.

author: LeoUCDavis
author_rank: Contributor
timestamp: January 01, 2016, 05:05:12 am
content: Quote from: G0HZU on January 01, 2016, 12:58:53 amLooks very nice. I see several listings on eBay that claim a working condition. Maybe I'll get one of them to find out. Thanks for all the helpful information.

author: G0HZU
author_rank: Super Contributor
timestamp: January 01, 2016, 04:54:20 pm
content: Note that if you already have access to a few modern thermocouple power meters you probably aren't adding any useful day to day value by getting a thermistor based power meter.The thermistor sensors do require care to avoid damage and they also require regular and careful zeroing. Also, on the sensitive power ranges the zero will drift if you handle the sensor (thermal effects) or even if you move the whole meter/cable/sensor assembly. So you may need to keep zeroing the meter several times a minute on the lower ranges! The 432A has an auto zero feature which helps a bit here but you still need to allow time to zero itself regularly. It really is a labour of love to use them as a day to day power meter and these are some of the reasons they aren't used any more in modern RF labs.Also, the interconnecting cable between the sensor and meter can be quite hard to find and a good one can be expensive because of this. The cable can also be intermittent. Some of this stuff is 40-50 years old.I just use mine as a cross checking meter. If I was seriously into calibration like some of the calibration petrolheads are on here then I suppose I would have tried cross checking via DC substitution. But I have many references and sources here that I can cross check to adequate confidence without needing to do this.However, for some people on here, calibration is like a religion (make your cheques payable to 'Calibration Heaven') and they chase down every $$$ avenue that gets more and more accuracy in terms of voltage and frequency etc etc. It's almost as if calibration 'is' the hobby

author: acbern
author_rank: Frequent Contributor
timestamp: January 02, 2016, 04:15:00 pm
content: Quote from: G0HZU on January 01, 2016, 04:54:20 pmWell, I guess you miss the point. The initiator of this posting was asking how to avoid costs for calibration of equipment. I would assume that they do this (getting gear calibrated) to get a meter that they know is within (certain) specs. Otherwise it would be useless. He was not asking: is calibration necessary?Now of course not everybody needs calibrated equipment for all their measurement jobs. You can write a physics document about e.g. a new theory or basic research without it. You cannot do that if you have e.g. re-measured a certain particle parameter to achieve a better accuracy. It all depends on what you do. And it certainly has nothing to do with 'calibration is the hobby' (except for those who have it as a hobby, if these exist, and thats fine too).But if you negate the need for calibration for those who need it (for whatever reason, and as the initiator of the post), then in deed all calibration is worthless and a waste. Certainly not an engineering/scientific approach.

author: G0HZU
author_rank: Super Contributor
timestamp: January 02, 2016, 05:43:41 pm
content: I wasn't missing the point. I drew a stark contrast between my needs and the extreme needs of some others. It's up to the individual to decide what they 'need'. If I want to make a humerous comment about it then that's up to meI've offered up the methods I use (and the limitations). It's up to the OP to decide if any of the info is useful.QuoteThat was a pretty lame strawman IMO