Author Topic: DE/EU Simple LM399 Reference Board, improved second Version  (Read 10875 times)

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Offline RoadRunner

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DE/EU Simple LM399 Reference Board, improved second Version
« on: November 16, 2018, 09:35:29 pm »
A little while ago i made a quick LM399 based reference board and posted on the forum. Many people have made few suggestion.
So here the improved board.
Now it has reverse polarity protection using P-MOSFET with Power status LED

Good quality 1K Pot in series with 10PPM 20K register for output voltage adjust-ability.
Because LM399 initial tolerance is only 2% , feedback resistor value depend on LM399 initial calibration , it may range form 8.2K to 9.5K



PCB Gerber and source file are available here
https://github.com/circuitvalley/LM399_Voltage_reference

https://www.circuitvalley.com/2018/11/diy-open-source-lm399-V2-voltage-reference-10v-dmm-calibrate.html

There a little video description show you temperature plot over 17 hours with temperature ranging from 14 to 27 degree C.
« Last Edit: November 09, 2020, 07:41:23 pm by RoadRunner »
 
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Offline RoadRunner

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Re: DE/EU Simple LM399 Reference Board, improved second Version
« Reply #1 on: November 16, 2018, 09:37:21 pm »


Here is one unit which was shipped to one forum member from previous batch.
 

Offline RoadRunner

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Re: DE/EU Simple LM399 Reference Board, improved second Version
« Reply #2 on: November 19, 2018, 05:10:50 pm »
3 sold in one go , only two remaining
 

Offline RoadRunner

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Re: DE/EU Simple LM399 Reference Board, improved second Version
« Reply #3 on: November 28, 2018, 02:16:03 pm »
Does any one want, Last one before Christmas?
 

Offline Iwanushka

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Re: DE/EU Simple LM399 Reference Board, improved second Version
« Reply #4 on: November 30, 2018, 12:58:12 am »
I will take it.
When all you've got is a hammer, everything starts looking like a nail.- Attrition.
 

Offline RoadRunner

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Re: DE/EU Simple LM399 Reference Board, improved second Version
« Reply #5 on: November 30, 2018, 03:49:18 pm »
I will take it.

Sorry , All Gone for now, next batch after Chirstmas.
 

Offline mk_

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Re: DE/EU Simple LM399 Reference Board, improved second Version
« Reply #6 on: December 02, 2018, 10:12:43 am »
I will take it.

Sorry , All Gone for now, next batch after Chirstmas.

 if Iwanushka is in a urgent need for the device then I will wait for the next batch even if the money arrived on your account during the next days.

 

Offline branadic

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If someone is looking for a LMx99 based 10V reference, I should receive some boards of a PWM based voltage reference soon, hopefully next week.

https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg1955149/#msg1955149

-branadic-
Metrology Meeting 2020 is canceled. Looking forward for MM2021
 

Offline Iwanushka

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Re: DE/EU Simple LM399 Reference Board, improved second Version
« Reply #8 on: December 04, 2018, 02:24:41 am »
I will take it.

Sorry , All Gone for now, next batch after Chirstmas.

 if Iwanushka is in a urgent need for the device then I will wait for the next batch even if the money arrived on your account during the next days.

Mate, thanks for your kind offer, but I'm not in a hurry I can wait for the next batch.
When all you've got is a hammer, everything starts looking like a nail.- Attrition.
 

Offline mk_

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Parcel arrived well packed, testing later this weekend

Thanks a lot

Michael

 

Offline RoadRunner

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Board is back in stock if someone needs one please drop a pm.

Thanks
 

Offline toastedcrumpets

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Pm sent, I'd like one please
 

Offline RoadRunner

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Pm sent, I'd like one please
you got one, Few still available.
 

Offline hellzakk

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I'll take one
 

Offline RoadRunner

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Offline nfmax

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Mine arrived safely this morning and is currently being tested. I'm using an HP 34401A which was last calibrated by Keysight on 8th January, and has a history of very good accuracy on the 10V range. At last calibration, it read 10.00002 V from a 10.0 V source (with an uncertainty of 0.000076 V). Allowing a couple of hours for the meter to warm up, then turning on the reference, gives me readings of around 10.00003V after 2 hours. It's varying a bit, but that is probably with room temperature. I'm logging that, and I will analyse the results later. The specification accuracy for the meter (10V range, 90 day) is 0.00025 V, so it is doing much better than it needs to!

:)
 

Offline RoadRunner

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Mine arrived safely this morning and is currently being tested. I'm using an HP 34401A which was last calibrated by Keysight on 8th January, and has a history of very good accuracy on the 10V range. At last calibration, it read 10.00002 V from a 10.0 V source (with an uncertainty of 0.000076 V). Allowing a couple of hours for the meter to warm up, then turning on the reference, gives me readings of around 10.00003V after 2 hours. It's varying a bit, but that is probably with room temperature. I'm logging that, and I will analyse the results later. The specification accuracy for the meter (10V range, 90 day) is 0.00025 V, so it is doing much better than it needs to!

:)

I am sure and happy that it matches the specs, Glad that you liked,
More boards available if anyone in need.

Few boards also available now with LM399H for and 42 EUR shipped within DE 45 EUR shipped worldwide. While LM399AH version priced at 50EUR DE and  53 EUR shipped worldwide.
 

Offline DC1MC

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Is it possible to to get one as close as possible to 10V ?

 Cheers,
 DC1MC
 

Offline RoadRunner

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Is it possible to to get one as close as possible to 10V ?

 Cheers,
 DC1MC

If i undstand correctly. You are asking about if output voltage is tunable? This is second version of the board. Previously there was no pot to for adjustment, now there a 1K pot to make fine adjusment to the low tempco gain resistors.  it is possible now tune voltage to 10.00000V.

Regards
« Last Edit: January 25, 2019, 08:54:13 pm by RoadRunner »
 

Offline toastedcrumpets

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OK, I just received my purchase, the shipping was fast, you can see it took 11 days from saying I want one to it arriving!

I ordered the 50 euro board. I wanted a separate voltage reference to compare my recently repaired Fluke 3330B and my Keysight 34461A against.

However, between ordering this board and it arriving I actually upgraded from a 34461A to a DMM7510  :-DMM This means i can do some serious testing of this reference.

I warmed up the DMM7510 for 90 mins and performed an ACAL. I then plugged the board into my bench PSU, first removing it from its anti-static bag, but returning it to its foam padding to reduce air currents and started logging! 5 NPLC and moving average of 20 points as recommended by the meter for maximum precision.

On startup there's a rapid transient followed by a slow drift upwards over time, but the voltage is accurate to 10ppm, which is quite impressive given its just been posted, ripped open and popped on.

Roadrunner, can you comment if you age these references at all? I'm going to leave it connected to my meter for a day or two and see what the performance is like over a longer time and will post again!
 

Offline RoadRunner

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OK, I just received my purchase, the shipping was fast, you can see it took 11 days from saying I want one to it arriving!

I ordered the 50 euro board. I wanted a separate voltage reference to compare my recently repaired Fluke 3330B and my Keysight 34461A against.

However, between ordering this board and it arriving I actually upgraded from a 34461A to a DMM7510  :-DMM This means i can do some serious testing of this reference.

I warmed up the DMM7510 for 90 mins and performed an ACAL. I then plugged the board into my bench PSU, first removing it from its anti-static bag, but returning it to its foam padding to reduce air currents and started logging! 5 NPLC and moving average of 20 points as recommended by the meter for maximum precision.

On startup there's a rapid transient followed by a slow drift upwards over time, but the voltage is accurate to 10ppm, which is quite impressive given its just been posted, ripped open and popped on.

Roadrunner, can you comment if you age these references at all? I'm going to leave it connected to my meter for a day or two and see what the performance is like over a longer time and will post again!

All Boards were aged only around 4-5 days right before i calibrate and calibration is done right 1-2 days before i ship actually handover package to post.
I let board sit in free air, no any airflow arround but also with no extra insulation or anything like that.

 

Offline toastedcrumpets

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I let board sit in free air, no any airflow arround but also with no extra insulation or anything like that.

I believe insulation is a good idea as in free air any small oscillations in the air flow can carry over to the package surface temperature, then into the package itself. This causes oscillations in the power to the heater which then causes oscillations elsewhere (i.e. heating lines or resistors). With insulation, these oscillations are damped, and then you only have to deal with the slowly varying lab temperature changes, which hopefully are negated by your low tempco resistors.
 

Offline toastedcrumpets

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Just an update. The board has been on since it arrived and seemed to settle just below 10V at 9.99997.

I logged the voltage over night during a lab temperature change from 21 to 18C, with a humidity close to 25%.
You can see the drop in temperature quite clearly as a drop in voltage. I'm guessing it settled below 10V as you have a warmer lab than I do IIRC.

I'm quite happy with this performance and will now look to make a small insulated case for it to better reduce the dependence on lab temperature, then I'll trim the pot just a little to see if I can get it closer to my 10V.

One happy customer, thanks again!
 

Offline RoadRunner

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Just an update. The board has been on since it arrived and seemed to settle just below 10V at 9.99997.

I logged the voltage over night during a lab temperature change from 21 to 18C, with a humidity close to 25%.
You can see the drop in temperature quite clearly as a drop in voltage. I'm guessing it settled below 10V as you have a warmer lab than I do IIRC.

I'm quite happy with this performance and will now look to make a small insulated case for it to better reduce the dependence on lab temperature, then I'll trim the pot just a little to see if I can get it closer to my 10V.

One happy customer, thanks again!
:-+ Danke
 

Offline nfmax

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #24 on: February 03, 2019, 09:41:57 am »
Mine arrived safely this morning and is currently being tested. I'm using an HP 34401A which was last calibrated by Keysight on 8th January, and has a history of very good accuracy on the 10V range. At last calibration, it read 10.00002 V from a 10.0 V source (with an uncertainty of 0.000076 V). Allowing a couple of hours for the meter to warm up, then turning on the reference, gives me readings of around 10.00003V after 2 hours. It's varying a bit, but that is probably with room temperature. I'm logging that, and I will analyse the results later. The specification accuracy for the meter (10V range, 90 day) is 0.00025 V, so it is doing much better than it needs to!

:)

Finally got around to crunching the numbers & plotting the results! One vertical division on the volts axis is one LSD of the 34401A meter display. The meter had been on since about 11:00. At 12:15 or so I went into the lab and turned up the thermostat. I started logging both voltage and temperature at that time, but didn't turn the reference on until about 12:35. The thermostat timer turns the heating off at 18:00. Although the board was just sat on the bench, without a case or cover, it doesn't seem much affected by the room temperature.

There are a few spikes (e.g. around 17:50 & at 20:29) where I was at the bench. Some of them directly relate to turning other equipment and lights on & off. I made an initial zero test, with power off, and during this I observed that the board - specifically the input protection MOSFET - seems to be light sensitive. A bright desk light just above it gave a few microvolts output from the reference. Presumably the DS diode in the MOSFET was acting as a photodiode, and although the epoxy package is black, it's very thin. It is possible the offset voltage of the output amplifier may also be slightly photosenstive. Voltnuts may want to remove the LED before putting it in a screened, light-tight box!

 

Offline Mr. Scram

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #25 on: February 03, 2019, 03:51:03 pm »
Finally got around to crunching the numbers & plotting the results! One vertical division on the volts axis is one LSD of the 34401A meter display. The meter had been on since about 11:00. At 12:15 or so I went into the lab and turned up the thermostat. I started logging both voltage and temperature at that time, but didn't turn the reference on until about 12:35. The thermostat timer turns the heating off at 18:00. Although the board was just sat on the bench, without a case or cover, it doesn't seem much affected by the room temperature.

There are a few spikes (e.g. around 17:50 & at 20:29) where I was at the bench. Some of them directly relate to turning other equipment and lights on & off. I made an initial zero test, with power off, and during this I observed that the board - specifically the input protection MOSFET - seems to be light sensitive. A bright desk light just above it gave a few microvolts output from the reference. Presumably the DS diode in the MOSFET was acting as a photodiode, and although the epoxy package is black, it's very thin. It is possible the offset voltage of the output amplifier may also be slightly photosenstive. Voltnuts may want to remove the LED before putting it in a screened, light-tight box!
I love that even a fairly "mundane" multimeter like the 34401A can show the presence of people in a room by measuring the small deviations they bring about in other electronics. The diode finding is also very interesting!
 

Offline RoadRunner

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #26 on: February 04, 2019, 09:23:21 am »
Mine arrived safely this morning and is currently being tested. I'm using an HP 34401A which was last calibrated by Keysight on 8th January, and has a history of very good accuracy on the 10V range. At last calibration, it read 10.00002 V from a 10.0 V source (with an uncertainty of 0.000076 V). Allowing a couple of hours for the meter to warm up, then turning on the reference, gives me readings of around 10.00003V after 2 hours. It's varying a bit, but that is probably with room temperature. I'm logging that, and I will analyse the results later. The specification accuracy for the meter (10V range, 90 day) is 0.00025 V, so it is doing much better than it needs to!

:)

Finally got around to crunching the numbers & plotting the results! One vertical division on the volts axis is one LSD of the 34401A meter display. The meter had been on since about 11:00. At 12:15 or so I went into the lab and turned up the thermostat. I started logging both voltage and temperature at that time, but didn't turn the reference on until about 12:35. The thermostat timer turns the heating off at 18:00. Although the board was just sat on the bench, without a case or cover, it doesn't seem much affected by the room temperature.

There are a few spikes (e.g. around 17:50 & at 20:29) where I was at the bench. Some of them directly relate to turning other equipment and lights on & off. I made an initial zero test, with power off, and during this I observed that the board - specifically the input protection MOSFET - seems to be light sensitive. A bright desk light just above it gave a few microvolts output from the reference. Presumably the DS diode in the MOSFET was acting as a photodiode, and although the epoxy package is black, it's very thin. It is possible the offset voltage of the output amplifier may also be slightly photosenstive. Voltnuts may want to remove the LED before putting it in a screened, light-tight box!

The diode finding is interesting to me as well, i will myself look into this. will share if i can come up with some results.
 

Offline DC1MC

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #27 on: February 04, 2019, 11:42:33 am »
Mine arrived safely this morning and is currently being tested. I'm using an HP 34401A which was last calibrated by Keysight on 8th January, and has a history of very good accuracy on the 10V range. At last calibration, it read 10.00002 V from a 10.0 V source (with an uncertainty of 0.000076 V). Allowing a couple of hours for the meter to warm up, then turning on the reference, gives me readings of around 10.00003V after 2 hours. It's varying a bit, but that is probably with room temperature. I'm logging that, and I will analyse the results later. The specification accuracy for the meter (10V range, 90 day) is 0.00025 V, so it is doing much better than it needs to!

:)


Finally got around to crunching the numbers & plotting the results! One vertical division on the volts axis is one LSD of the 34401A meter display. The meter had been on since about 11:00. At 12:15 or so I went into the lab and turned up the thermostat. I started logging both voltage and temperature at that time, but didn't turn the reference on until about 12:35. The thermostat timer turns the heating off at 18:00. Although the board was just sat on the bench, without a case or cover, it doesn't seem much affected by the room temperature.

There are a few spikes (e.g. around 17:50 & at 20:29) where I was at the bench. Some of them directly relate to turning other equipment and lights on & off. I made an initial zero test, with power off, and during this I observed that the board - specifically the input protection MOSFET - seems to be light sensitive. A bright desk light just above it gave a few microvolts output from the reference. Presumably the DS diode in the MOSFET was acting as a photodiode, and although the epoxy package is black, it's very thin. It is possible the offset voltage of the output amplifier may also be slightly photosenstive. Voltnuts may want to remove the LED before putting it in a screened, light-tight box!

The diode finding is interesting to me as well, i will myself look into this. will share if i can come up with some results.

No so long ago there was RPi2 that was actually fully rebooting because of a "transparent" package of the power regulator:
https://www.alphr.com/raspberry-pi-2/1000375/why-a-camera-flash-will-reboot-your-raspberry-pi-2

It seem that the quality of the IC packaging went down together with the price :(

 Cheers,
 DC1MC
 

Offline cowasaki

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #28 on: February 17, 2019, 03:58:26 pm »
I would like one of these too. What is the size of the board. I’ll read the thread fully later, I take it the power requirements are in the thread.
 

Offline RoadRunner

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #29 on: February 17, 2019, 05:25:42 pm »
I would like one of these too. What is the size of the board. I’ll read the thread fully later, I take it the power requirements are in the thread.

You got one, size is 48x100mm.
 
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Offline not1xor1

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #30 on: February 18, 2019, 07:38:20 am »
I would like one of these too. What is the size of the board. I’ll read the thread fully later, I take it the power requirements are in the thread.

You got one, size is 48x100mm.

So you selected the wrong country in your account profile... obviously you are from Flatland  :D

Apart of jokes do you plan to go on selling these boards for some more time?
I would like to buy one in 3-4 months (I have to move stuff around because of home renovation, HEPA filtered ventilation system).
 

Offline toastedcrumpets

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #31 on: February 18, 2019, 09:30:13 am »
Power requirements are low, it takes 0.15A at 15V initially while the heater is getting everything up to temperature, then it settles below 0.025A  for me. You may get different results depending on air temperature and the level of insulation you have.
 

Offline RoadRunner

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #32 on: February 18, 2019, 10:25:48 am »
I would like one of these too. What is the size of the board. I’ll read the thread fully later, I take it the power requirements are in the thread.

You got one, size is 48x100mm.

So you selected the wrong country in your account profile... obviously you are from Flatland  :D

Apart of jokes do you plan to go on selling these boards for some more time?
I would like to buy one in 3-4 months (I have to move stuff around because of home renovation, HEPA filtered ventilation system).

I do have only limited time in hand to do extra stuff , so as long as something else more important does not come up it shoud be available,  3-4 Months is long time to say something.
« Last Edit: February 21, 2019, 10:58:51 am by RoadRunner »
 
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Offline jpb

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It arrived today - thank you RoadRunner.

I've not insulated it but I've fed it through an LT3042 board I got from ebay to give it a low noise 15V supply.
My 2015 is dead on and my 2000 is reading between 2 and 3 in the last digit.

I'm very pleased though I'm not sure I like the power sockets which seem to require a fat probe to be stuck in rather than the thin wires I was trying to use - perhaps I'm using them wrong.

Sorry for the out-of-focus shot of the board.

Edit : the 2000 now seems steady at 2 and occasionally down to 1 in the last digit.
« Last Edit: March 01, 2019, 09:32:34 pm by jpb »
 

Offline cowasaki

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Hoping mine arrives tomorrow.  I have spare 20v AC transformers and a batch of triple DC output PCBs I designed for another project.  Basically the transformer output is rectified then an electrolytic cap for positive and another for negative rails, space for a small cap per output, switching and output.  The two main rails are to 7812/7912 regs then a 7805 giving the three outputs.  If I build one with a 7815 and forget the neg rail it should give a perfectly stable 15v DC.  How good does the supply voltage have to be?  Is this up to it?  If so I have some nice cases so will build it up tomorrow.
 

Offline jpb

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I don't know how good the supply should be.

I just used a (modified) LT3042 board because they are cheap on ebay (I went for a UK supplier which was £12 because I was in a hurry but the ones direct from China are less than £6). I desoldered the 33K surface mount resistor and used a Vishay 150k also off ebay. Probably way over the top but as the thing is a reference I thought it was worth over engineering.

I intend to use a supply like you suggest but make it 18V instead of 15V and use it to feed the LT3042 board.
« Last Edit: March 01, 2019, 10:55:27 pm by jpb »
 

Offline jpb

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As a postscript to my earlier post, I now find my meter probe is stuck in the connector! I managed to pull out three of them but not the fourth.

So be careful not to use probes as connectors - just straight thick wire I guess.

I must say I do not like these push connectors, I will probably have to desolder at least one to retrieve my probe. Going on the Wago web site I see that there is a special tool needed to remove wires.

RoadRunner - was there a particular reason for selecting these connectors?

EDIT : after pushing down hard on the white button and pulling hard on the probe it has now come out (though I did bend it in the process) So problem solved.
I intend putting the board in a box with terminals so might connect these with thick copper wire (I hope this doesn't lead to emf issues arising from different metals).
« Last Edit: March 01, 2019, 11:29:20 pm by jpb »
 

Offline cowasaki

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I don't know how good the supply should be.

I just used a (modified) LT3042 board because they are cheap on ebay (I went for a UK supplier which was £12 because I was in a hurry but the ones direct from China are less than £6). I desoldered the 33K surface mount resistor and used a Vishay 150k also off ebay. Probably way over the top but as the thing is a reference I thought it was worth over engineering.

I intend to use a supply like you suggest but make it 18V instead of 15V and use it to feed the LT3042 board.

I designed the board and only actually wanted 1 with a spare but when I went to put the order in it was 80p more for 10 so I went with that and they sent 11 anyway.  Somewhere I have about 7 or 8 taped together with a piece of masking tape.  If I find them soon enough you can have one for the postage.  The BOM is 4 x diodes, 1 x regulator, 1 x electrolytic cap (maybe 1000-2200) and I have a 100nF plus an LED and to 4 way headers.  If I find the boards soon enough I'll chuck all the bits in other than the electrolytic and regulator for you but obviously you will need a transformer giving maybe 3v more than your reg.


EDIT:  Just added the schematic below and image of the board.  With the USB isolation section empty this is the PSU I'll be using with the negative rail gone, a 7815 instead of the 7812 and no 7805 :)
« Last Edit: March 01, 2019, 11:35:48 pm by cowasaki »
 

Offline jpb

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I don't know how good the supply should be.

I just used a (modified) LT3042 board because they are cheap on ebay (I went for a UK supplier which was £12 because I was in a hurry but the ones direct from China are less than £6). I desoldered the 33K surface mount resistor and used a Vishay 150k also off ebay. Probably way over the top but as the thing is a reference I thought it was worth over engineering.

I intend to use a supply like you suggest but make it 18V instead of 15V and use it to feed the LT3042 board.

I designed the board and only actually wanted 1 with a spare but when I went to put the order in it was 80p more for 10 so I went with that and they sent 11 anyway.  Somewhere I have about 7 or 8 taped together with a piece of masking tape.  If I find them soon enough you can have one for the postage.  The BOM is 4 x diodes, 1 x regulator, 1 x electrolytic cap (maybe 1000-2200) and I have a 100nF plus an LED and to 4 way headers.  If I find the boards soon enough I'll chuck all the bits in other than the electrolytic and regulator for you but obviously you will need a transformer giving maybe 3v more than your reg.
Thank you for the very kind offer, but I'm probably OK as I have an external (unregulated linear) supply  which is basically a transformer plus diodes and electrolytic capacitor I was planning to use and then I'll just mount my 18V regulator in the box (that is my current plan - use the box as a heat sink).
 

Offline cowasaki

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My board arrived this morning.

I'm about 1/3 of a mV out at 10v on the Keithley 2100 about the same the other way on the PM2525. (I had to swap the power leads round).
« Last Edit: March 05, 2019, 07:01:45 pm by cowasaki »
 

Offline jpb

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My board arrived this morning.

I'm about 1/3 of a mV out at 10v on the Keithley 2100 about the same the other way on the PM2525. (I had to swap the power leads round).
I haven't checked the specs on a Keithley 2100, but that difference seems quite large. Was everything warmed up for a while?

The closeness of my results I think was slightly fortuitous as my study was quite warm (from equipment running in various experiments I'm doing) and I think RoadRunner calibrates at quite a warm 24C (that is from memory - perhaps I have that wrong) but I would still expect the variation to be a few 10s of microVolts not 300 or so.
 

Offline cowasaki

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My board arrived this morning.

I'm about 1/3 of a mV out at 10v on the Keithley 2100 about the same the other way on the PM2525. (I had to swap the power leads round).
I haven't checked the specs on a Keithley 2100, but that difference seems quite large. Was everything warmed up for a while?

The closeness of my results I think was slightly fortuitous as my study was quite warm (from equipment running in various experiments I'm doing) and I think RoadRunner calibrates at quite a warm 24C (that is from memory - perhaps I have that wrong) but I would still expect the variation to be a few 10s of microVolts not 300 or so.

It was on for hours.  I've had it on again tonight and it's 9.99954 now

So my only other reference is a £4 10v ebay reference so show here 2nd we get..

So 2100 reads 9.99954 & 10.00590
The PM2525 reads  10.002 & 10.010
The UT60E reads 10.00 & 10.01
The UNI-T 4102C reads 9.99 & 10.00

Now we have 9.99965  when I switched it on cold it read 10.00118

It is just sat on the desk connected to my bench power supply which is set to 15.00123 (using the 2100)
« Last Edit: March 06, 2019, 08:23:34 pm by cowasaki »
 

Offline cowasaki

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According to my 4 wire PT100 probe on the 2100 the temperature is 27.197 or 27.1 with the infra-red thermometer

The temp of the LM399AH is 29.7 using the probe or 29.9 using the thermometer
 

Offline RoadRunner

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My board arrived this morning.

I'm about 1/3 of a mV out at 10v on the Keithley 2100 about the same the other way on the PM2525. (I had to swap the power leads round).
I haven't checked the specs on a Keithley 2100, but that difference seems quite large. Was everything warmed up for a while?

The closeness of my results I think was slightly fortuitous as my study was quite warm (from equipment running in various experiments I'm doing) and I think RoadRunner calibrates at quite a warm 24C (that is from memory - perhaps I have that wrong) but I would still expect the variation to be a few 10s of microVolts not 300 or so.

Yes it seems to be quite large, Most of people i get feedback from had variation with there insturment around +/- 100 micro volts, Since toastedcrumpets pointed out ,now During calibration i cover board with 3 CM think foam, while ambieant temprature around 22C.

Regards
 

Offline cowasaki

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My board arrived this morning.

I'm about 1/3 of a mV out at 10v on the Keithley 2100 about the same the other way on the PM2525. (I had to swap the power leads round).
I haven't checked the specs on a Keithley 2100, but that difference seems quite large. Was everything warmed up for a while?

The closeness of my results I think was slightly fortuitous as my study was quite warm (from equipment running in various experiments I'm doing) and I think RoadRunner calibrates at quite a warm 24C (that is from memory - perhaps I have that wrong) but I would still expect the variation to be a few 10s of microVolts not 300 or so.

Yes it seems to be quite large, Most of people i get feedback from had variation with there insturment around +/- 100 micro volts, Since toastedcrumpets pointed out ,now During calibration i cover board with 3 CM think foam, while ambieant temprature around 22C.

Regards

So what should I do with it as best practice? Cover it in foam in a sealed box? I can do that but wouldn’t the temperature be higher. Is my temp the reason for the low figure? The device showed a higher figure earlier before the heat increased.

Thanks.
 

Offline kado

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Hi,

i have two boards and realised, that the 10 V output voltage varies in the 100s uV if the 15V input change in 100s mV below the 15V checkpoint.

Karsten


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Offline RoadRunner

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Hi,

i have two boards and realised, that the 10 V output voltage varies in the 100s uV if the 15V input change in 100s mV below the 15V checkpoint.

Karsten


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Thanks for pointing, yes power supply need to be as close as possible to 15V.

Regards
 

Offline DC1MC

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Hi,

i have two boards and realised, that the 10 V output voltage varies in the 100s uV if the 15V input change in 100s mV below the 15V checkpoint.

Karsten

Is the reverse true as well, if the 15V increases over 15V the variation goes as well ?

 DC1MC
 

Offline cowasaki

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Hi,

i have two boards and realised, that the 10 V output voltage varies in the 100s uV if the 15V input change in 100s mV below the 15V checkpoint.

Karsten


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Thanks for pointing, yes power supply need to be as close as possible to 15V.

Regards

Well the 10V board also makes a good thermometer :)

Attached is the board when the temperature is 24.5C and the voltage is 15.0+- 0.05V

10uV out which is much more like what I expected.  I'm going to build a new 15v board and wrap the ref board and stick it in it's own box but with my reference resistors as well :)

EDIT: Just read that....  So is it better to be 0.1V over than a little under?  OR as close as possible..... and just HOW close?

ALSO....  Is it safe to wrap it up in foam?  I don't want to damage it by overheating the board or anything like that.

Thanks


This is now in the range of ..... which is out, the reference or the DMM? :-)
« Last Edit: March 07, 2019, 04:45:08 pm by cowasaki »
 

Offline kado

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Tune down slowly your 15V feeding source and you will get a exact 10.00000 reading. If thats the way to go with a calibration source i am not sure.
Was myself astonished about that behaviour.

Karsten


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Offline RoadRunner

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Hi,

i have two boards and realised, that the 10 V output voltage varies in the 100s uV if the 15V input change in 100s mV below the 15V checkpoint.

Karsten


Gesendet von iPhone mit Tapatalk

Thanks for pointing, yes power supply need to be as close as possible to 15V.

Regards

Well the 10V board also makes a good thermometer :)

Attached is the board when the temperature is 24.5C and the voltage is 15.0+- 0.05V

10uV out which is much more like what I expected.  I'm going to build a new 15v board and wrap the ref board and stick it in it's own box but with my reference resistors as well :)

EDIT: Just read that....  So is it better to be 0.1V over than a little under?  OR as close as possible..... and just HOW close?

ALSO....  Is it safe to wrap it up in foam?  I don't want to damage it by overheating the board or anything like that.

Thanks


This is now in the range of ..... which is out, the reference or the DMM? :-)

One volt difference in Supply voltage makes around 180uV difference in output because of reference zener diode current.
 

Offline cowasaki

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Hi,

i have two boards and realised, that the 10 V output voltage varies in the 100s uV if the 15V input change in 100s mV below the 15V checkpoint.

Karsten


Gesendet von iPhone mit Tapatalk

Thanks for pointing, yes power supply need to be as close as possible to 15V.

Regards

Well the 10V board also makes a good thermometer :)

Attached is the board when the temperature is 24.5C and the voltage is 15.0+- 0.05V

10uV out which is much more like what I expected.  I'm going to build a new 15v board and wrap the ref board and stick it in it's own box but with my reference resistors as well :)

EDIT: Just read that....  So is it better to be 0.1V over than a little under?  OR as close as possible..... and just HOW close?

ALSO....  Is it safe to wrap it up in foam?  I don't want to damage it by overheating the board or anything like that.

Thanks


This is now in the range of ..... which is out, the reference or the DMM? :-)

One volt difference in Supply voltage makes around 180uV difference in output because of reference zener diode current.

In that case I need to build another power supply.  I've got one on KiCAD at the moment which would do it based on the LT3080ET.....  Maybe that's the way to go.
 

Offline jpb

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My 15V was about 14.998V.

I used a LT3402 board from E-bay and a 150kohm Vishay resistor also from ebay (Note a LT3405 board provides more current but are about twice the price):

relatively expensive UK sourced which I used because I was in a hurry
https://www.ebay.co.uk/itm/LT3042-Ultra-low-Noise-Ultra-high-20V-200mA-PSRR-RFLinear-Regulator-Power-Module/142890461926?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
much cheaper straight from China
https://www.ebay.co.uk/itm/20V-200mA-Ultra-Low-Noise-LT3042-PSRR-RF-Linear-Regulator-Power-Module-K/283132638364?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

NB I had to desolder the setting resistor from the board and also connect the enable pin with the wire as shown in the picture on my earlier post.
https://www.ebay.co.uk/itm/Vishay-S102C-150K-0-01-Metal-Foil-Resistors/352563629910?ssPageName=STRK%3AMEBIDX%3AIT&var=621889264013&_trksid=p2060353.m1438.l2649
« Last Edit: March 08, 2019, 06:33:06 pm by jpb »
 

Offline kado

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jbp

thanks for the detailed information and links!

Bye the way: where could one buy those fine dual banana cables? Never find them until now.

Karsten


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Offline jpb

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jbp

thanks for the detailed information and links!

Bye the way: where could one buy those fine dual banana cables? Never find them until now.

Karsten


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They are pomona ones - they are quite expensive new but I buy them if I see them going cheap on ebay - most of the time ebay is more expensive than digikey so beware!:
They come in different lengths e.g.
https://www.digikey.co.uk/product-detail/en/pomona-electronics/2BA-24/501-1696-ND/736429
 

Offline cowasaki

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It arrived today - thank you RoadRunner.

I've not insulated it but I've fed it through an LT3042 board I got from ebay to give it a low noise 15V supply.
My 2015 is dead on and my 2000 is reading between 2 and 3 in the last digit.

I'm very pleased though I'm not sure I like the power sockets which seem to require a fat probe to be stuck in rather than the thin wires I was trying to use - perhaps I'm using them wrong.

Sorry for the out-of-focus shot of the board.

Edit : the 2000 now seems steady at 2 and occasionally down to 1 in the last digit.

Do you have the schematic or other information regarding the ebay board?
 

Offline jpb

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Do you have the schematic or other information regarding the ebay board?
I don't but it there is a lot of information on the LT3042 datasheet:
https://www.analog.com/media/en/technical-documentation/data-sheets/3042fb.pdf
I think the board is pretty close to the schematic on the datasheet first page.

I just blundered around unsoldering resistors (and accidentally unsoldering and resoldering a capacitor!) until the output was determined by the external resistor I had soldered. The board is clearly labelled underneath as shown in the attached photo. I think it was R6 I had to unsolder. You can also follow the traces from the chip if your eyesight is up to it (mine is getting a little dodgy now-a-days!)

You also need to connect the enable to positive VIN (check on the datasheet).

It would be neater to just connect enable to VIN on the underside of the board.

I left the resistor legs very long for two reasons - one I thought I might want to use it for something else if it didn't work well on the board and secondly to avoid over-heating it when soldering (I also used a copper crocodile clip as a heat sink).

Of course, you can also fit a switch between VIN and Enable if you want to turn the thing on and off.
« Last Edit: March 16, 2019, 09:03:45 pm by jpb »
 

Offline jpb

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Offline grizewald

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I've cased mine as well, but as I always power the reference with a bench supply, I didn't need to add any other components, just a plug for the supply and a pair of 4mm plugs for the output.

The dimensions of the board are a little unfortunate as it doesn't fit inside any of the standard Hammond cases which are also tall enough. So, all I did was make a little foam igloo to keep the LM399 and it's leads warm and cosy and 3D print a couple of plastic rails to adapt the board to the case.

  Lord of Sealand
 

Offline alex-sh

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The dimensions of the board are a little unfortunate as it doesn't fit inside any of the standard Hammond cases which are also tall enough. So, all I did was make a little foam igloo to keep the LM399 and it's leads warm and cosy and 3D print a couple of plastic rails to adapt the board to the case.


Well, I am not so sure about unfortunate dimension. Did you measure it correctly?
This is the same LM399 board cased into Hammond 1455C1201. It is a tight fit though - I do not think you can squeeze in anything else.

« Last Edit: April 23, 2019, 10:54:01 am by alex-sh »
 

Offline grizewald

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Well, I am not so sure about unfortunate dimension. Did you measure it correctly?

 ::)

With the insulation I added around the LM399 and allowing for the board to be held in the lowest slots on the inside of the case, the remaining 18.5mm in height was not enough. This is why I included the phrase "which are also tall enough".

Maybe your LM399 is mounted closer to the PCB than mine. Did you add any insulation around the reference to quickly stabilise the temperature and avoid convection effects?
« Last Edit: April 23, 2019, 04:08:49 pm by grizewald »
  Lord of Sealand
 

Offline alex-sh

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Maybe your LM399 is mounted closer to the PCB than mine. Did you add any insulation around the reference to quickly stabilise the temperature and avoid convection effects?

I am not sure how close my LM399 is mounted to the board compare to yours.
Yes, mine is fully insulated. In fact I put in a lot of insulation material. However, the problem I had was not height. The problem I had was length. With the banana plugs I have used, it was difficult to put it all together.
 

Offline TA2AWX

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Hi, good project. I recently salvaged 2 LM399AH2s from a junkyard board and thinking of making this. I readily have OP07CP opamps in my parts bin, do you think they could replace LT1001 in this project?

Thanks!
 

Offline ZhuraYuk

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Won't variable resistor make tuned voltage incorrect due high TCR and overall instability of element, like vibrations? Maybe better decision to measure it resistance and then replace with some vishay constant value resistors?
 
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Offline pizzigri

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #64 on: September 29, 2020, 12:33:02 pm »
Roadrunner, do you still have these boards?
 

Offline RoadRunner

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Re: (Back in Stock) DE/EU Simple LM399 Reference Board, improved second Version
« Reply #65 on: September 29, 2020, 05:49:59 pm »
Roadrunner, do you still have these boards?

Yes only few boards are still available , As there is worldwide shortage of LM399AH.
 

Offline pizzigri

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Received my board a couple of days ago, and placing it in a box with good insulation.
A question: where to get GOOD female contacts for input/output?
Another thing, is there a problem in using an all-plastic ox or do I need also shielding?
Heres a pic of how the ref is coming along.
I made a double insulation chamber, and suspended the board using vibration absorbing rubber loops used in microphones.

 

Online coromonadalix

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Good setup,  the board suspenders are killer  :-+

I dont think the lm399 is prone to emi interferences ?  personally i would have used an metallic box,  but if the box  is not mishandled or thrown on the floor it should be ok ?

gurus here may have another view(s) ?
 

Offline cowasaki

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I have a metal box within a rack unit in my workshop which contains the reference.  I'm have built a decent 15v power supply and a circuit which has Botha lower and higher temperature setting.  The temperatures are correct with my platinum probe to the keithley and the heater kicks in as soon as the temperature dips below the minimum and turns off as the temperature goes above the maximum.  BUT I have a big over shoot in temperature which I believe is probably due to the heater element I am using which is probably too large.

Question 1 - What is the best range to use?

Question 2 - What is a reasonable heating element?
 


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