Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

   

Here's first pass schematic for a precision 190mv, 1.9V, and 19V reference. I decided to go with a design so each voltage could be very precisely set individually for maximum accuracy. It's a higher parts count but not really all that more complex. Now to generate a parts list and  get an order in.

Feel free to provide input/suggestions.   

Edit.....I'm going to put a design thought for a 500VDC reference on paper too. Watch this space. 

DANGER!!!
50,000 OHMS!!!
 

mnem
*Unbalanced input*

[Martin.M]

washing is done, it looks much better now.
Found that for 10,-€

[med6753]

Martin, that's a cool looking DMM but that side selector switch is really funky. 

[med6753]

DANGER!!!
50,000 OHMS!!!
 

mnem
*Unbalanced input*

Don't you mean DANGER......500 VOLTS....IDIOT AT WORK? 

Loving this retirement. I get to play all day long. The 190VDC reference has been cooking for hours and it never exceeds +/- 30mV from nominal. 

[Specmaster]

Martin, that's a cool looking DMM but that side selector switch is really funky. 

And side power entry, limits where it can be located though[emoji53]

[mnementh]

washing is done, it looks much better now. Found that for 10,-€

"When I grow up, I wanna be a Fluke."

Hey bean -

You were right about not needing hairspray. Now I got the bed temp set at 70°C, it preheats to ~60°C measured on the surface of the glass in ~3-5 minutes. After an hour or so of printing, it'll creep up and measure right on 70°C. I'm on number 7 now; once the glass cools a few minutes, part pops off by itself and then just a quick scrape with a razor and wipe with a paper napkin.

mnem
Number 7... number 7... number 7...

[Specmaster]

No No, your number 6 number 6 number 6 

[tautech]

washing is done, it looks much better now.
Found that for 10,-€

That will look nice paired with one of your teeny weeny Teks Martin. 

A pic of them together please.

[URI]

Still won't lock.   

Does it output position data on the serial port?

Back to explore my two Trimble 57963-D GPSDO boards.

Strangely I found the GPSDO I left unlocked before I left for work locked after I came back.   
Because I had it on my todo list I built a DB9 adapter for my spare board and connected both GPSDOs to my computer (now) running Lady Heather.
I had to configure Heather online because she didn't want to process the heather.cfg file, even the COM port was not processed.. 

After that I could see what the problem is:
The encased GPSDO often tracked tracked 2 satellites fewer than my spare board. As a result the encased GPSDO is in hold mode more often.
Why it did lose lock? -I don't know.
Could be a restart because of a power sag at a time when it couldn't track enough satellites?

My location is a bit bad for receiving GPS signals:
My apartment is at street level and the GPS antennas are on the window sill of a window that's looking out to the west and onto the street where on the other side (~25m distance) there's an apartment building with 4 floors.
My apartment doesn't have windows to the south or to the north.   
As a result GPS signals seem to come in weak.
My encased GPSDO sees an average of 3 sats maxing to 6 and sometimes none where my spare board never loses contact and at least tracks a minimum of 2 sats.

I'm curious how the BG7TBL will handle this situation...

[PA0PBZ]

My location is a bit bad for receiving GPS signals:
My apartment is at street level and the GPS antennas are on the window sill of a window that's looking out to the west and onto the street where on the other side (~25m distance) there's an apartment building with 4 floors.
My apartment doesn't have windows to the south or to the north.   

That is far from ideal, maybe you should try to find a way to bring an antenna outside and up, but that could be hard depending on landlord and regulations…

[bd139]

I’ve got one of these. https://www.sotabeams.co.uk/telescopic-masts-sotapoles-7m-and-10m/

Stuff it on the end and run a cable down the middle.

Hard to complain about a temporary structure. At least here. My neighbour hates my HF antenna but I don’t give a shit

[URI]

My location is a bit bad for receiving GPS signals:
My apartment is at street level and the GPS antennas are on the window sill of a window that's looking out to the west and onto the street where on the other side (~25m distance) there's an apartment building with 4 floors.
My apartment doesn't have windows to the south or to the north.   

That is far from ideal, maybe you should try to find a way to bring an antenna outside and up, but that could be hard depending on landlord and regulations…

Errrm. The antennas are on the outside window sill. Didn't describe that clearly.
Inside the window it doesn't work at all thanks to energy saving window glass that's metallized to keep the infrared inside.

And yes, I can't mount them outside on e.g. an console that brings them away from the buildings wall to "see" more of the sky.
My landlord wouldn't even allow me to install a new telephone cable from my apartment to the basement even though the telephone cabling is old and rotten and not suited for 100MBit VDSL... In that case I just did it anyway and camouflaged the new cable (running along with other cables) with white colour and some dirt.   
An installation of a console for my GPS antennas facing to the street can't be camouflaged in any way, so no chance for me. 

I have put some copper plated board underneath the antennas and will exchange that with 5mm strong steal plates -those will stay where I put them even if there's strong wind (strong winds actually already moved my GPS antennas..).

[med6753]

Here's a first pass at a possible 500VDC reference. Basically uses two Smakn inverters in series as opposed to the 190VDC reference which used one. Since the input and output of the inverters is common they both must be totally isolated from each other or the result would be magic smoke. The quickest and safest way to do this is separate battery supplies.

The adjust resistor values on the regulator adjust pins need to be determined. One regulator would fixed at approx 250VDC and the other would have an adjust trim pot to set the output at exactly 500VDC. I see no reason why this wouldn't work and when I get a chance I'm going to cobble it together. 

[mnementh]

Not feeling brave enough to fully series-stack the inverters and run 'em both off a single 36V supply, eh? 

mnem
*Star Wars time*

[med6753]

Not feeling brave enough to fully series-stack the inverters and run 'em both off a single 36V supply, eh? 

mnem
*Star Wars time*

You can't. The -V in and -V out are common. As soon as I tied -V out of one to +V in of the other....KABOOM 

[0culus]

500 V with even a little current behind it is bound to hurt.

[med6753]

500 V with even a little current behind it is bound to hurt.

It sure will. I am compromising with that value. Some DMM's specify 750V or 1KV to calibrate their upper range. I ain't that stupid. 

[Specmaster]

Did I miss the 190V schematic somewhere along the line?

[med6753]

Did I miss the 190V schematic somewhere along the line?

I did a while back but that was a prototype. Here's the final "as built" version.

[beanflying]

Here's first pass schematic for a precision 190mv, 1.9V, and 19V reference. I decided to go with a design so each voltage could be very precisely set individually for maximum accuracy. It's a higher parts count but not really all that more complex. Now to generate a parts list and  get an order in.

Feel free to provide input/suggestions.   

KISS  Needs a bit more complexity on the trim pots whose temp co's are generally horrid. Consider using lower value pots and additional low temp co fixed resistors to get it in the ballpark.

[mnementh]

Not feeling brave enough to fully series-stack the inverters and run 'em both off a single 36V supply, eh? 

mnem
*Star Wars time*

You can't. The -V in and -V out are common. As soon as I tied -V out of one to +V in of the other....KABOOM 

Do the outputs NEED to be tied together? Each of the LR8s has reference back to its own inverter power supply. Either leg should be floatable. Then you can actually ground the (-) output rail while using a transformer-based power supply.

mnem
Mmmm... floating 500VDC... yummy.  *tzzzzt* 

[bd139]

Last time I did anything like that I used a 240->24v transformer and connected the secondary to the secondary of a 9v->240v. That booted out about 750V DC after rectification and smoothing.

Check transformer rating though. Shitty ones tend to flash over.

[URI]

Still won't lock.   

Does it output position data on the serial port?

With Lady Heather now continuously running I can observe how both units track the same satellites but the encased one eventually switched to hold mode with "PLL init" message while the spare board stays locked all the time.   

Thank goodness I ordered another GPSDO..   

[med6753]

Here's first pass schematic for a precision 190mv, 1.9V, and 19V reference. I decided to go with a design so each voltage could be very precisely set individually for maximum accuracy. It's a higher parts count but not really all that more complex. Now to generate a parts list and  get an order in.

Feel free to provide input/suggestions.   

KISS  Needs a bit more complexity on the trim pots whose temp co's are generally horrid. Consider using lower value pots and additional low temp co fixed resistors to get it in the ballpark.

I can get the trim pots cheap so I'll also order up some 5K trimmers and add 5K fixed in series and see if it makes a difference.

[beanflying]

How are you going to solder them in close proximity to that thermoplastic? Seems highly unlikely you won't uglify the hell right out of it.

Tacked them together to make them stay in place easier while I work on the strip copper links. So Far So Good

Good work on losing the hairspray. Good squirt and wipe of IPA between prints to keep any skin oils away from the glass and wash it every dozen or so prints just because. Glassy finish and no glue gunk