USA Cal Club: Round 2

[bitseeker]

Ok, we'll see how it goes. Thanks, TiN.

[bitseeker]

I saw an anomalous temp sample scroll by today: 86°C

For a moment, I thought something had gone Fahrenheit all of a sudden.

[bitseeker]

I grabbed a copy of the log now that it has gone past 24 hrs to see what the data looks like. There's definitely something up with the Tempduino. It gets huge spikes in temp data (cropped them off in the attached charts) on a regular basis and the measured temperature thereafter suffers an offset until the next spike. Very strange.

The temperature value also seems to be about 2°C higher than my DMMs report.

TiN, I uploaded the temp copy in case you want to chart it: log_2019-06-24_190620.tmp.csv

[TiN]

Vertical axis labels making those charts rather useless 

I prefer scaling vertical axis on my plots in ppm deviation from the reference point for two reasons:
* Graph difference 2.5 ppm vs 5.5 ppm is easy to follow, then something like 7.2345089 to 7.2345306 V  . At least for me 
* Showing absolute values like 7.2345306 without expensive traceability to SI volt is rather pointless, as typical accuracy of hobby labs ends at 5th digit, so providing higher resolution numbers have only relative value.

According to the data, your 34401A box TC is -0.79 ppm/K.

Maybe something turns on nearby, like AC or dehumidifier or neightbour's welding supply, causing your thermometer to go nuts? For time being, before you fix the root cause you can add a hack to provide clean data, add a check "if (temp > 40c) : retry temp measurement again". Also why temperature changes in "steps". Almost looks like you restart data capture every X samples, missing some time in between.. 

Here is code for plotter I used.
It needs Python 2.7, matplotlib, numpy, scipy.

[bitseeker]

Vertical axis labels making those charts rather useless 

Those were just quick Excel charts to see, qualitatively, what the data was like, and revealed the recurring temperature data anomalies. So, not useless for what I wanted to see. Hence, I uploaded the raw data for your much better plotter program.

I prefer scaling vertical axis on my plots in ppm deviation from the reference point for two reasons:
* Graph difference 2.5 ppm vs 5.5 ppm is easy to follow, then something like 7.2345089 to 7.2345306 V  . At least for me 
* Showing absolute values like 7.2345306 without expensive traceability to SI volt is rather pointless, as typical accuracy of hobby labs ends at 5th digit, so providing higher resolution numbers have only relative value.

Yes, definitely better axes.

According to the data, your 34401A box TC is -0.79 ppm/K.

34401A or 34410A? Seems the 34410A varies inversely with the temperature.

Maybe something turns on nearby, like AC or dehumidifier or neightbour's welding supply, causing your thermometer to go nuts? For time being, before you fix the root cause you can add a hack to provide clean data, add a check "if (temp > 40c) : retry temp measurement again". Also why temperature changes in "steps". Almost looks like you restart data capture every X samples, missing some time in between.. 

I'm not familiar with this Arduino-based temperature/humidity unit that's part of the cal kit. It's the first time I've used it. So, I'm not sure what this might be. There's no nearby AC. Maybe my neighbor does have a new welder.

My logger fetches a sample from the Tempduino every time it gets readings from the DMMs. So, no lost time on the logging end. It looks like the firmware or the sensor may be resetting something at the time of the glitch and then the temperature reading "corrects" itself. Interestingly, the humidity readings do not exhibit this behavior.

The anomalous temperature reading goes too low as well as too high. However, the glitch appears as an integer value instead of the expected float. So, I'll check for that condition and retry when it appears.

Here is code for plotter I used.
It needs Python 2.7, matplotlib, numpy, scipy.

Cool. I'll check it out.

Thanks for the feedback and tips!

[bitseeker]

Added the anomalous temp check, swapped the vrefs, and started logging again.

[vindoline]

There's definitely something up with the Tempduino. It gets huge spikes in temp data (cropped them off in the attached charts) on a regular basis and the measured temperature thereafter suffers an offset until the next spike. Very strange.

The temperature value also seems to be about 2°C higher than my DMMs report.

Yeah, that's defiantly not right. To be honest, I didn't check out the Tempduino at all (I already have a temp/humidity logging setup). I just plugged in 5v to see that it "worked" and put it back in the box. The weird "noise" spikes are one thing, but I really don't like how the baseline shifts around. That makes it pretty useless 

[rhb]

I don't have any temperature control or logging facility.  Both are on the ToDo list.  So I'm planning on just making differential measurements on my 8 references and checking my DMMs.

When the kit reaches me I'll spend some time investigating the Tempduino.  I should have all the parts for one, so I can probably test everything and sort out what is going on.

I'd only expected to keep the kit for a few days, but if the Tempduino needs some attention I'm happy to do that.  IIRC I got a bunch of high quality thermistors a few months ago as part of a larger order.  And thermocouples are readily available from the hardware store.

[bitseeker]

Hi rhb. Are you next on the list? That'll be great if you can check out the Tempduino.

I took a closer look at the temp and humidity data since I noticed that I didn't put my fix for the bad temp values in the right place last night. Corrected that and continued logging.

Both sensors show baseline offsets at the same time. However, only the temperature has the crazy values. Humidity values never spike (neither up nor down), they just shift at the same time that the temp shifts.

The anomalies occur every 2 hours, 20 minutes, and approximately 10 seconds (~8410 seconds). The number of seconds varies a bit because my logger records every time the DMMs finish their 100 PLC and place their values onto the GPIB bus (approximately every 3–4 seconds).

Oof, my script just died because it got an incomplete record from the Tempduino (no humidity data). That's the first time that's happened after approximately 40 hours of logging. I'll have to add a regex pattern to verify that the string received matches the expected format prior to extracting the values from it. Actually, it looks like the Tempduino died. The display went blank. Rebooting!

What do you need for logging, rhb? There's a GPIB interface in the kit and a couple of PCBs to make your own, if you want.

[hwj-d]

Perhaps it's an arduino software issue. In any case, one should look at its source code and the data sheets of the sensors, regarding time behavior over i2c or spi.

[bitseeker]

Yep. This time, I had the received values logged to the console when bad data arrived. The string format is "temp,humidity,checksum". Looks like there were a couple of cases when the data was incomplete.

(2:20:14h) 2019-06-26 14:37:10 | 34401A: +1.00002190E+01  34410A: +7.04570976E+00  24.994°C  46.904%
Error: Received unexpected output from Tempduino [34,46.891,3ba6]
Error: Received unexpected output from Tempduino [91]
(2:20:17h) 2019-06-26 14:37:14 | 34401A: +1.00002180E+01  34410A: +7.04571001E+00  24.997°C  46.872%
Error: Received unexpected output from Tempduino [39,46.851,28af]
Error: Received unexpected output from Tempduino [dd]
(2:20:21h) 2019-06-26 14:37:17 | 34401A: +1.00002180E+01  34410A: +7.04571120E+00  25.000°C  46.855%
Error: Received unexpected output from Tempduino [37,46.812,4a19]
(2:20:24h) 2019-06-26 14:37:21 | 34401A: +1.00002190E+01  34410A: +7.04570987E+00  25.439°C  46.794%

[VNUTDENYER]

Hi all, just need some info on test setups.  What interface to GPIB, which SW preferred for logging, tolerance / tracking of dual supply, temp stability needed/preferred, and ?  Plan to use E1410A in VXI mainframe with 3478A for PS and Tempduino measurements both under GPIB control (if I can get a USB dongle to check operation).  Is the list on first page original or already random sort (can figure how much time left for setup)?  Thanks again for any upfront advice on making tests useful (maybe not just to me).

[rhb]

I'm next.  I need another project like I need another hole in my head, but I'll look into the problem.  Major shift from lathe spindle bearing design though.  I'm rebuilding a new 7x14 Chinese mini-lathe as a precision instrument lathe so I can make go/no-go gauges for Chinese  RF connectors. The lathe was  delivered as a complete set of partially finished castings which was assembled at the factory to make sure they don't leave out a part.

I have 2x 34401A, 2x 3478A, 3x LM399 from Jason, 3x AD584JH from eBay and a couple of Doug Malone's references.  And I've fixed bugs in 2.5 million lines of other people's code.  So I have a reasonable chance of resolving the logger issue.

[bitseeker]

Hi all, just need some info on test setups.

Hi there. Sure, I'll answer what I can. Others will hopefully fill the gaps.

What interface to GPIB,

I'm using an Agilent 82357B USB-to-GPIB adapter.

which SW preferred for logging

I started out using BenchVue, but writing my own in Python with PyVISA enabled me to synchronize the DMM readings with temperature and humidity data. I can also extend it to log non-HPAK instruments (i.e., anything VISA-compatible), which BenchVue doesn't support.

So, there's no particular preference/requirement. It's up to your personal preference and/or equipment requirements.

tolerance / tracking of dual supply,

For the FX reference, I'm using an HP E3631A set at ±12 VDC. TiN, who provided the reference, stated that a "Decent quality linear bench PSU will be fine. For critical measurements (e.g. noise) I use two VRLA 12V batteries."

For the PX reference, I'm using an HP 6114A precision power supply set at 15 VDC. It powers the reference's own voltage regulator, included in the kit.

You can see pics in this post: https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg2498784/#msg2498784

temp stability needed/preferred

I don't have a strictly temp-controlled lab at home. I guess this depends more on what you want to measure. Different environments could be interesting to see how the equipment behaves.

Plan to use E1410A in VXI mainframe with 3478A for PS and Tempduino measurements both under GPIB control

Note that the Tempduino communicates via USB.

(if I can get a USB dongle to check operation).

The kit includes an ATmega 328-based USB-to-GPIB adapter. I'm not familiar with its operation.

Is the list on first page original or already random sort (can figure how much time left for setup)?  Thanks again for any upfront advice on making tests useful (maybe not just to me).

I read back through the thread and this was the last list that was posted: https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg2321592/#msg2321592

Vindoline is managing, so he would have the most up-to-date information on the participant list and the order.

[bitseeker]

Since I've just gone back through all the posts in this thread, I gathered a "Getting Started" list of posts about the USA Cal Club kit, its contents, and setup. If I missed anything, PM me and I'll update this.

USA Cal Club kit contents (what's in the box and how it's arranged)
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg2459097/#msg2459097
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg2472399/#msg2472399

Resistor references (installed on the lid of the PX voltage reference)
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg2409894/#msg2409894

FX voltage reference
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg2423187/#msg2423187

PX voltage reference
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg1501783/#msg1501783

PX reference's power regulator (use this to power the reference for consistency between participants)
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg1516537/#msg1516537

Tempduino (temperature and humidity)
https://www.eevblog.com/forum/metrology/usa-cal-club-round-2/msg1511497/#msg1511497

[bitseeker]

I'm next.  I need another project like I need another hole in my head, but I'll look into the problem.

I hear ya about projects. Your help is very much appreciated. I'm not sure what code is running on Tempduino or where to get it. Since cellularmitosis made it, I checked his two GitHub accounts, but didn't see anything that looked like it might be it.

https://github.com/cellularmitosis
https://github.com/pepaslabs

Major shift from lathe spindle bearing design though.  I'm rebuilding a new 7x14 Chinese mini-lathe as a precision instrument lathe so I can make go/no-go gauges for Chinese  RF connectors. The lathe was  delivered as a complete set of partially finished castings which was assembled at the factory to make sure they don't leave out a part.

What is this go/no-go gauge: To see if an RF connector was made so far out of spec as to damage the connector it would be mated with?

I have 2x 34401A, 2x 3478A, 3x LM399 from Jason, 3x AD584JH from eBay and a couple of Doug Malone's references.

Cool. If you have GPIB cables, then give the included USB-to-GPIB interface a try. I haven't tried it, so I'm not sure what software is needed to interface with it. It doesn't have VISA drivers that I'm aware of. Maybe it's Prologix compatible.

And I've fixed bugs in 2.5 million lines of other people's code.  So I have a reasonable chance of resolving the logger issue.

Excellent! Just the right man for the job.

[SirAlucard]

Do we have an up to date list of participants?

Also I think it's a great idea to have documentation regarding best practices to test and whatnot for us people new to the cal club.

[VNUTDENYER]

Thanks bitseeker.  Will plan on dual deep cycle SLA for +-12v, 15v linear for 10v,  USB for temp with included firmwar, etc.  Still need to load some logging app and test it and rig some shade on lab (camper).  May have to move into basement if too hot.  Do "we" have a feel for how long minimum temp should be stable before meaningful readings can be taken?  Is detoxit needed on copper leads for ultimate resolution (not by me    )?  Thanks again.

[rhb]

I hear ya about projects. Your help is very much appreciated. I'm not sure what code is running on Tempduino or where to get it. Since cellularmitosis made it, I checked his two GitHub accounts, but didn't see anything that looked like it might be it.

https://github.com/cellularmitosis
https://github.com/pepaslabs

I'll pester Jason if needed.  Can't be much to it.

What is this go/no-go gauge: To see if an RF connector was made so far out of spec as to damage the connector it would be mated with?

Precisely.  I was testing a batch of Chinese 50 ohm SMA terminators with a Tek 11801 and 20 GHz SD-26 and the male pin pulled out of one! The 11801/SD-26 combination is amazing for checking RF stuff.  You can evaluate the devices as fast as you can connect them.  At least, you can if you know what the time domain response should be.

Making the gauges is easy relative to rebuilding a 7x14 Chinese minilathe to hold tolerances of 0.0002".  I'm still collecting the required tooling, but I think it will be a fun project.  I don't expect to get much better than 0.001" on the first pass as I don't have adequate temperature control. But that's OK.  The whole point is to take on  a project sufficiently difficult that I learn lots of things in the process.

I've owned a 10x20 Clausing lathe and 6x24 mill for 20 years.  So I have a pretty good notion of what I'm attempting.  What's amazing to me is the nasty attitude on the 7x12minilathe list on groups.io.  They bad mouth the machine at every opportunity and my post analyzing the spindle bearings was greeted with contempt as being "reading rather than doing".  I'm not an ME, but the more I study the machine, the more impressed I am with the design.  It was designed to meet a *very* low price point.   Every decision was guided by manufacturing cost and expected level of buyer's skills. As delivered for under $550 US it's just a complete parts kit, assembled at the factory to make sure they don't leave out any parts.  But with appropriate modification and a skilled user it need apologize to no one.  There is plenty of iron where it is needed.  The major compromises are in the ergonomics of infrequent adjustments such as tailstock setover for cutting tapers.

In the late 1940's, David Broadhead, an amateur, was engaged by John Strong, one of the preeminent experimental physicists of the day,  to make the screws for a ruling engine Strong was building at Johns Hopkins.  In preparation for the work, Broadhead rebuilt his 13" Southbend to eliminate all periodic spindle errors and make the ways straight and parallel to 0.0001".  The screws were tested by interferometer to less than a millionth of an inch.  After the screws were turned, they were lapped.  The June & July 1952  issues of Scientific American have some fantastic articles about it.

At 6e-6"/"-F expansion, it doesn't take a lot of temperature differential to blow through 200e-6".  The really attractive part of rebuilding a mini-lathe to such tolerances is it's a *lot* smaller.  I plan to recondition my Clausing lathe , but I probably won't go past 0.0005" because of the size.

All the fasteners need to be replaced and some serious work done to true it up, but I know of nothing else that can touch it.  A used name brand machine will require as much or more work and parts are much harder to get.  I had planned to document the rebuild on the groups.io forum, but I'm looking for an alternative which is more pleasant.  The list has 15,000+ members, but only about 2 dozen who are active and *very* unpleasant and outright hostile.  As best I can tell, they simply BS about YouTube videos they watch.  And occasionally mangle there lathes a bit more with some poorly thought out modification.

I have IDC connectors and ribbon cable.  I just have not made GPIB cables up yet as I don't have an interface or a multiplexer.  I've got all the parts, but have not gotten around to it.

[Conrad Hoffman]

Sounds like a fun project and you know full well what's required. Stay away from Practical Machinst, as they'll trash any of the low cost imports, though some have gotten away with it recently. You might find The Home Machinist much friendlier, though the traffic is lower- https://www.chaski.org/homemachinist/index.php

What PM does have is Richard King, who probably knows more about scraping than anybody.

[bitseeker]

Also I think it's a great idea to have documentation regarding best practices to test and whatnot for us people new to the cal club.

I'll get something together before I send the kit back to vindoline. I may post it independent of this thread (e.g., USA Cal Club Getting Started Guide), since this thread is titled for Round 2. That way it can be evergreen regardless of round number.

Do "we" have a feel for how long minimum temp should be stable before meaningful readings can be taken?  Is detoxit needed on copper leads for ultimate resolution (not by me    )?  Thanks again.

Temp stability requirement depends on your equipment. Unless you have some really high-end gear, the vrefs are much more stable than the equipment measuring them.

No DeoxIT necessary that I'm aware of. I didn't have to do anything with any of the connectors. Several of them are gold-plated.

[VNUTDENYER]

Thanks again bitseeker.

[SirAlucard]

Quick question as this doesn't really belong in this thread, but does anyone here mind if I message them about some equipment questions?

[Grandchuck]

I would be happy to answer, or try to answer, questions.

[SirAlucard]

I would be happy to answer, or try to answer, questions.

I appreciate the offer, but I was looking to talk to someone that's been actively involved with the USA Cal Club for quite a while.