EEVblog® Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: TylerPeppy on August 16, 2026, 10:52:01 pm
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Crosspost from a TE thread from earlier...
I Finally got around to building my new uDR1399 reference boards. They use bootstrapping and an LT5400 to set the amplifier gain. Both of those are things I would have wanted to see in the already available standards like the TEN-399 board and VREF10. I may be incorrect on what the VREF10 uses, so feel free to correct me. They have only burned in for about 72hrs so far, but seem to be humming along stabily. The results are from unit 1 of 3 that I have built.
I will edit and reiterate what is mentionned on the GitHub docs in spite of issues. As of current, do NOT connect a battery or other live supply to the unit while making connections. I tend to use a linear power supply and use the ON / OFF control of the channel to turn the uDR1399 unit on after connecting. Please add a 47uF electrolytic across the input posts if you wish to do so. There is a known issue where transients resulting from the hotplugging of the power cables can cause transients exceeding the LT3045's maximum inputs.
Unit 2 is reserved for Josh, but unit 3 can be spoken for if someone wishes to test a reference like this.
I measured using my DMM6500 on 10NPLC, 10 sample averaging DCV filter, AZ on, and 10GOhm InZ. Sensing is done through Banana-BNC adapters, and the internal wiring in my refs are twisted pair to the Pomona 3770 plugs. The STD-Dev running is using 1799 samples (or what 10NPLC for 30s would work out to, not including averaging filter) as suggested by iMO. The noise is high compared to the 34465A, but I have gotten ~4.15uV STD-Dev when disabling AZ, which is contrary to results we've seen so far in this thread.
More info can be found on my GitHub where I documented everything about the project: https://github.com/T-622/uDR1399-10V-Reference-Standard/tree/main (https://github.com/T-622/uDR1399-10V-Reference-Standard/tree/main)
Stability test results can be found here: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/ (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller)
Josh has one of the reference boards, and is testing it with a Keithley 2010, 34465A, and DAQ6510. He has reported numerous sets of findings, highlighting the temperature stability of the boards, and the overall noise within 30min windows on a Keithley 2010 to be <1uV std-dev. I am also attempting to build a thermal chamber to test the temperature coeffecient of the voltage output. This is proving quite difficult.
Tests Conducted:
1.) Josh's Initial Tests: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6332874/#msg6332874 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6332874/#msg6332874)
Results Using 34465A For Best Stability:
Moving Filter:
2min - 10 Sample Moving Filter: 582nV std-dev
50min - 10 Sample Moving Filter: 727nV std-dev
75min - 10 Sample Moving Filter: 753nV std-dev
100min - 10 Sample Moving Filter: 751nV std-dev
No Moving Filter?:
018min - 2.92445uV std-dev
030min - 3.02086uV std-dev
040min - 2.90277uV std-dev
075min - 2.63610uV std-dev
100min - 2.46730uV std-dev
2.) Josh's Continued Test of 10 Sample Moving Filter: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333148/#msg6333148 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333148/#msg6333148)
Using 34465A:
* Note: These sets of tests featured a lot of thermal variance in the uDR1399's environment temperature, and the thermal influence on the reference was relatively minimal.
075min - 10 Sample Moving Filter: 785nV std-dev
128min - 10 Sample Moving Filter: 817nV std-dev
267min - 10 Sample Moving Filter: 1.61831uV std-dev
360min - 10 Sample Moving Filter: 2.04978uV std-dev
500min - 10 Sample Moving Filter: 2.92553uV std-dev
3.) Battery Bank + Keithley 2750: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333938/#msg6333938 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333938/#msg6333938)
No Filter:
40min warmup: 2.56582uV std-dev. I wouldn't count this one, as the reference was still warming up. However, it appeared to reach relative stability within a 16.67min window.
Test 4: 2min Filter ON: 811uV std-dev
Test 5: 2min Filter ON: 866nV std-dev
Test 6: Filter is 10 sample moving average (?) 1799 sample std-dev moving used in TestController.
2min - Filter ON: 347nV std-dev
10min - Filter ON: 677nV std-dev
30min - Filter ON: 848nV std-dev
100min - Filter ON: 668nV std-dev
4.) Tyler - DMM6500. 10 Sample moving avg filter, AZ ON, 10V range, 10PLC: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335186/#msg6335186 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335186/#msg6335186)
* Note: My reference featured here has been burning in for 432hrs at this point of measurement.
140min - Filter On: 2.906uV std-dev. Very little temperature variation
5.) Josh - Keithley 2010 Test: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736)
Test 1: 10PLC, 10 sample filter enabled, 1799 sample std-dev-running enabled.
2min - 612nV std-dev
5min - 654nV std-dev
10min - 677nV std-dev
638min - 875nV std-dev. 2010 Std-dev as measured by TC is 3.1577428uV.
Test 2: 10PLC, 10 sample filter enabled, 1799 sample std-dev-running enabled.
5min - 1.2195uV std-dev
Test 3:
5min - 803nV std-dev
10min - 671nV std-dev
15min - 711nV std-dev
Tyler
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You should link to specific posts by using the post title instead, for example: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736)
The /200 doesn't show the same for everybody depending on their display settings.
Thanks,
Josh
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You should link to specific posts by using the post title instead, for example: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736)
The /200 doesn't show the same for everybody depending on their display settings.
Thanks,
Josh
I have made some edits, included all the test until now that have been taken... And fixed links including specific posts instead.
Tyler
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Here's the last screenshot from Test 3 today before I shut it off.
Thanks,
Josh
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Crosspost from a TE thread from earlier...
I Finally got around to building my new uDR1399 reference boards. They use bootstrapping and an LT5400 to set the amplifier gain. Both of those are things I would have wanted to see in the already available standards like the TEN-399 board and VREF10. I may be incorrect on what the VREF10 uses, so feel free to correct me. They have only burned in for about 72hrs so far, but seem to be humming along stabily. The results are from unit 1 of 3 that I have built.
Unit 2 is reserved for Josh, but unit 3 can be spoken for if someone wishes to test a reference like this.
I measured using my DMM6500 on 10NPLC, 10 sample averaging DCV filter, AZ on, and 10GOhm InZ. Sensing is done through Banana-BNC adapters, and the internal wiring in my refs are twisted pair to the Pomona 3770 plugs. The STD-Dev running is using 1799 samples (or what 10NPLC for 30s would work out to, not including averaging filter) as suggested by iMO. The noise is high compared to the 34465A, but I have gotten ~4.15uV STD-Dev when disabling AZ, which is contrary to results we've seen so far in this thread.
More info can be found on my GitHub where I documented everything about the project: https://github.com/T-622/uDR1399-10V-Reference-Standard/tree/main (https://github.com/T-622/uDR1399-10V-Reference-Standard/tree/main)
Stability test results can be found here: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/ (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller)
Josh has one of the reference boards, and is testing it with a Keithley 2010, 34465A, and DAQ6510. He has reported numerous sets of findings, highlighting the temperature stability of the boards, and the overall noise within 30min windows on a Keithley 2010 to be <1uV std-dev. I am also attempting to build a thermal chamber to test the temperature coeffecient of the voltage output. This is proving quite difficult.
Tests Conducted:
1.) Josh's Initial Tests: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6332874/#msg6332874 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6332874/#msg6332874)
Results Using 34465A For Best Stability:
Moving Filter:
2min - 10 Sample Moving Filter: 582nV std-dev
50min - 10 Sample Moving Filter: 727nV std-dev
75min - 10 Sample Moving Filter: 753nV std-dev
100min - 10 Sample Moving Filter: 751nV std-dev
No Moving Filter?:
018min - 2.92445uV std-dev
030min - 3.02086uV std-dev
040min - 2.90277uV std-dev
075min - 2.63610uV std-dev
100min - 2.46730uV std-dev
2.) Josh's Continued Test of 10 Sample Moving Filter: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333148/#msg6333148 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333148/#msg6333148)
Using 34465A:
* Note: These sets of tests featured a lot of thermal variance in the uDR1399's environment temperature, and the thermal influence on the reference was relatively minimal.
075min - 10 Sample Moving Filter: 785nV std-dev
128min - 10 Sample Moving Filter: 817nV std-dev
267min - 10 Sample Moving Filter: 1.61831uV std-dev
360min - 10 Sample Moving Filter: 2.04978uV std-dev
500min - 10 Sample Moving Filter: 2.92553uV std-dev
3.) Battery Bank + Keithley 2750: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333938/#msg6333938 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333938/#msg6333938)
No Filter:
40min warmup: 2.56582uV std-dev. I wouldn't count this one, as the reference was still warming up. However, it appeared to reach relative stability within a 16.67min window.
Test 4: 2min Filter ON: 811uV std-dev
Test 5: 2min Filter ON: 866nV std-dev
Test 6: Filter is 10 sample moving average (?) 1799 sample std-dev moving used in TestController.
2min - Filter ON: 347nV std-dev
10min - Filter ON: 677nV std-dev
30min - Filter ON: 848nV std-dev
100min - Filter ON: 668nV std-dev
4.) Tyler - DMM6500. 10 Sample moving avg filter, AZ ON, 10V range, 10PLC: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335186/#msg6335186 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335186/#msg6335186)
* Note: My reference featured here has been burning in for 432hrs at this point of measurement.
140min - Filter On: 2.906uV std-dev. Very little temperature variation
5.) Josh - Keithley 2010 Test: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736)
Test 1: 10PLC, 10 sample filter enabled, 1799 sample std-dev-running enabled.
2min - 612nV std-dev
5min - 654nV std-dev
10min - 677nV std-dev
638min - 875nV std-dev. 2010 Std-dev as measured by TC is 3.1577428uV.
Test 2: 10PLC, 10 sample filter enabled, 1799 sample std-dev-running enabled.
5min - 1.2195uV std-dev
Test 3:
5min - 803nV std-dev
10min - 671nV std-dev
15min - 711nV std-dev
Tyler
Nice work!!
Did you consider installing a 3D printed cover that surrounds the ADR1399 top and bottom. This helps keep any thermals away from the 4 Kovar leads. Recall someone mentioning that slow thermals can build up and move around even in a "closed case". Having a regulator near by doesn't help either, we know we have linear regulator on our dual 10V reference (LM399 and LTZ1000) and another single 10V LM399 reference. We added the the 3D print cover but can't say for sure it's helped, but surely doesn't hurt!!
These new LM399 replacements seem worthwhile, and results seem to indicate such! Think we'll be getting a couple to checkout and compare to the other references we have.
Anyway, nice work and keep posting updates/results :-+
Best
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..you may see nice "jump(s)" in the graph above, whether they come from the Keithley 2010 or the 1399 module cannot be distinguished in this setup..
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..you may see nice "jump(s)" in the graph above, whether they come from the Keithley 2010 or the 1399 module cannot be distinguished in this setup..
Like I mentioned on another thread, I haven't seen the jumps in my boards I have left, as I cannot discern them from the DMM6500's noise. It will be interesting to see what jumps (if any) are seen on Martin's DMM7510.
Crosspost from a TE thread from earlier...
I Finally got around to building my new uDR1399 reference boards. They use bootstrapping and an LT5400 to set the amplifier gain. Both of those are things I would have wanted to see in the already available standards like the TEN-399 board and VREF10. I may be incorrect on what the VREF10 uses, so feel free to correct me. They have only burned in for about 72hrs so far, but seem to be humming along stabily. The results are from unit 1 of 3 that I have built.
Unit 2 is reserved for Josh, but unit 3 can be spoken for if someone wishes to test a reference like this.
I measured using my DMM6500 on 10NPLC, 10 sample averaging DCV filter, AZ on, and 10GOhm InZ. Sensing is done through Banana-BNC adapters, and the internal wiring in my refs are twisted pair to the Pomona 3770 plugs. The STD-Dev running is using 1799 samples (or what 10NPLC for 30s would work out to, not including averaging filter) as suggested by iMO. The noise is high compared to the 34465A, but I have gotten ~4.15uV STD-Dev when disabling AZ, which is contrary to results we've seen so far in this thread.
More info can be found on my GitHub where I documented everything about the project: https://github.com/T-622/uDR1399-10V-Reference-Standard/tree/main (https://github.com/T-622/uDR1399-10V-Reference-Standard/tree/main)
Stability test results can be found here: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/ (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller)
Josh has one of the reference boards, and is testing it with a Keithley 2010, 34465A, and DAQ6510. He has reported numerous sets of findings, highlighting the temperature stability of the boards, and the overall noise within 30min windows on a Keithley 2010 to be <1uV std-dev. I am also attempting to build a thermal chamber to test the temperature coeffecient of the voltage output. This is proving quite difficult.
Tests Conducted:
1.) Josh's Initial Tests: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6332874/#msg6332874 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6332874/#msg6332874)
Results Using 34465A For Best Stability:
Moving Filter:
2min - 10 Sample Moving Filter: 582nV std-dev
50min - 10 Sample Moving Filter: 727nV std-dev
75min - 10 Sample Moving Filter: 753nV std-dev
100min - 10 Sample Moving Filter: 751nV std-dev
No Moving Filter?:
018min - 2.92445uV std-dev
030min - 3.02086uV std-dev
040min - 2.90277uV std-dev
075min - 2.63610uV std-dev
100min - 2.46730uV std-dev
2.) Josh's Continued Test of 10 Sample Moving Filter: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333148/#msg6333148 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333148/#msg6333148)
Using 34465A:
* Note: These sets of tests featured a lot of thermal variance in the uDR1399's environment temperature, and the thermal influence on the reference was relatively minimal.
075min - 10 Sample Moving Filter: 785nV std-dev
128min - 10 Sample Moving Filter: 817nV std-dev
267min - 10 Sample Moving Filter: 1.61831uV std-dev
360min - 10 Sample Moving Filter: 2.04978uV std-dev
500min - 10 Sample Moving Filter: 2.92553uV std-dev
3.) Battery Bank + Keithley 2750: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333938/#msg6333938 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6333938/#msg6333938)
No Filter:
40min warmup: 2.56582uV std-dev. I wouldn't count this one, as the reference was still warming up. However, it appeared to reach relative stability within a 16.67min window.
Test 4: 2min Filter ON: 811uV std-dev
Test 5: 2min Filter ON: 866nV std-dev
Test 6: Filter is 10 sample moving average (?) 1799 sample std-dev moving used in TestController.
2min - Filter ON: 347nV std-dev
10min - Filter ON: 677nV std-dev
30min - Filter ON: 848nV std-dev
100min - Filter ON: 668nV std-dev
4.) Tyler - DMM6500. 10 Sample moving avg filter, AZ ON, 10V range, 10PLC: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335186/#msg6335186 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335186/#msg6335186)
* Note: My reference featured here has been burning in for 432hrs at this point of measurement.
140min - Filter On: 2.906uV std-dev. Very little temperature variation
5.) Josh - Keithley 2010 Test: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6335736/#msg6335736)
Test 1: 10PLC, 10 sample filter enabled, 1799 sample std-dev-running enabled.
2min - 612nV std-dev
5min - 654nV std-dev
10min - 677nV std-dev
638min - 875nV std-dev. 2010 Std-dev as measured by TC is 3.1577428uV.
Test 2: 10PLC, 10 sample filter enabled, 1799 sample std-dev-running enabled.
5min - 1.2195uV std-dev
Test 3:
5min - 803nV std-dev
10min - 671nV std-dev
15min - 711nV std-dev
Tyler
Nice work!!
Did you consider installing a 3D printed cover that surrounds the ADR1399 top and bottom. This helps keep any thermals away from the 4 Kovar leads. Recall someone mentioning that slow thermals can build up and move around even in a "closed case". Having a regulator near by doesn't help either, we know we have linear regulator on our dual 10V reference (LM399 and LTZ1000) and another single 10V LM399 reference. We added the the 3D print cover but can't say for sure it's helped, but surely doesn't hurt!!
These new LM399 replacements seem worthwhile, and results seem to indicate such! Think we'll be getting a couple to checkout and compare to the other references we have.
Anyway, nice work and keep posting updates/results :-+
Best
This is a very good point. For the time being, I only have made closed-cell foam plugs that cover the entire ADR1399 package in the boxes. I have the board step files, so making a cover that clips through the thermal relief cutouts wouldn't be all that difficult.
I mentioned this to Josh, and might create one in my spare time with PETG to see how it performs. As for the regulator, I kept the original placement as I had in my Rev01 boards. I figured if I placed it close to the gain setting components, I might create some more unintended drift.
I might do some thermal imaging with a macro lens to see how terribly the thermals from the regulator creep across the board. I was going to originally make the board longer, and more spaced out, but the Hammond 80x54mm enclosure was the target, so I had little room to work with.
Tyler
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..you may see nice "jump(s)" in the graph above, whether they come from the Keithley 2010 or the 1399 module cannot be distinguished in this setup..
True, but for the record, this K2010 also has an ADR1399. So the question is, which ADR1399? ;)
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..you may see nice "jump(s)" in the graph above, whether they come from the Keithley 2010 or the 1399 module cannot be distinguished in this setup..
True, but for the record, this K2010 also as an ADR1399. So the question is, which ADR1399? ;)
.. do use a low noise DUT which does not jump with your K2010. Simplest not-jumping-low-noise-DUT would be a battery, around 10-12V one. Let it run for a week/two while continuously sampling/logging and you will see.. ;)
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I think I should age my K2010 first for a year or two...after I'm done bastardizing it a little more. ;)
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I think I should age my K2010 first for a year or two...after I'm done bastardizing it a little more. ;)
What I would be interested to see rather, is the difference between an organically-aged reference, versus an accelerated-aged reference baked inside an oven. I would be interested to see if accelerated aging for a week is for example, better than organic aging for a month.
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The LM399 and ADR1399 references have the internal heater and run relatively hot (supposedly some 90 C) already. This is already close to the glass temperature of some epoxies. So going higher with an external oven may not be a good option. For these 2 references aging is mainly be having the reference powerd.
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..might be interesting to accelerate the aging of the entire "module" - there is the LT5400 divider, ie. how its epoxy package would respond to that..
PS: for example 12 days at 70C could be equivalent to something like ~1 year at ambient 25C..
PPS: the "jumping 1399" will not heal up (meaning it gets jumps-free) with aging, afaik..
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A main point with the epoxy packages, but also the PCB is humidity. Just heating for accelerated aging would also come with low relative humidity and this way drive out water. One may than see even more drift after the heated phase. When new the LT5400 like other plastic cases should start rather dry - high humidity in the plastic can cause issues with reflow soldering.
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I hope @TylerPeppy can forgive me...I might have changed the connection types on mine. ;)
Currently running off a 19.6VDC laptop power supply.
Thanks,
Josh
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I hope @TylerPeppy can forgive me...I might have changed the connection types on mine. ;)
Currently running off a 19.6VDC laptop power supply.
Thanks,
Josh
I would NEVER discourage modifications of my things, they *usually* only ever make them better. This is certainly one of those "cases" (ha!). I am eager to try these panels out as well, and potentially the Keystone 4109 versus my Pomona 3770s.
Tyler
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I would NEVER discourage modifications of my things, they *usually* only ever make them better. This is certainly one of those "cases" (ha!). I am eager to try these panels out as well, and potentially the Keystone 4109 versus my Pomona 3770s.
I know you don't mind; I was being like the Greek god Facetious. ;)
I like the 4109s better than the other ones we discussed, but the panels I made for the 4109s should accommodate all 3 and others.
I emailed you the data for 10 hours with the new panels/connections. I installed the gaskets normally. I think they're better as thermal gaskets than worrying about EMI. The panels still have continuity anyway.
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I designed a little cap for the ADR1399 as opposed to using traditional, closed-cell foam. This supports a maximum insertion height of 9.3mm of the ADR1399's case to the topside of the board.
The current version is a little more loose-fitting than I want, so I am going to dial down the tolerance compensation that I used in Fusion, but it seems to work fine. Once I have a tight-fitting part, I will attach and see if the performance changes.
Tyler
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Don't think you want a "tight fitting" cover, as this could cause some stress on the IC package. Ours is loose fitting (actually doesn't touch the case) and the cover is secured by the PCB slots (glued in place).
Best
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Don't think you want a "tight fitting" cover, as this could cause some stress on the IC package. Ours is loose fitting (actually doesn't touch the case) and the cover is secured by the PCB slots (glued in place).
Best
The original one had 0.2mm inwards offsets for the thermal relief holes so that the plug could mount properly using the cutouts. When I said "Tight fitting", I meant to refer that there is a bunch of room inside the case for the components, but the mounting holes were too loose. I have reprinted with 0.1mm and 0mm offsets to see how well. I typically use 0.2mm offsets on my Prusa MK3S+ and a 0.4mm nozzle, but sometimes these need tweaking.
Edit: The using 0mm of tolerance around the thermal cutout slots made for a snug but not overly tight fit for the cap. There is plenty of room around the component, and the ADR1399 is not impacted by the cap either.
- Tyler
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New thermal isolation caps have been installed around the 1399s, see the previous post for the .3mf file for the caps.
Updated data with these installed can be found here: https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6348896/#msg6348896 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6348896/#msg6348896)
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The new laser-cut and engraved end panels have been installed, and look great. These are Hammond Mfg. 1455CSALBK-10, and could be engraved on a cheap hobby CNC or laser engraver machine. Josh has the cutout files for multiple post types, and I will leave it up to him whether he wants to share them or not.
Tyler
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I dunno if I'd share that or not. I'll think about it.
A CNC might be able to cut that, but not a hobby laser. You need a decent fiber laser to cut metal. Any fiber or CO2 laser can do the engraving, but it's easier to setup on a galvo (as opposed to a gantry).
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I dunno if I'd share that or not. I'll think about it.
A CNC might be able to cut that, but not a hobby laser. You need a decent fiber laser to cut metal. Any fiber or CO2 laser can do the engraving, but it's easier to setup on a galvo (as opposed to a gantry).
Yes, of course. The cutting for an engraver might be easier to just mark the drill outline, and then drill by hand later if needed. I suspect this project will never garner nearly enough attention for that to be a thought/worry though.
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You could just order a PCB with black solder mask and the right cut outs and silkscreen text on it. Not as nice but much more accessible.
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We just 3D print the end plates and can add text as needed (don't have a Laser or CNC). If you need E-Field shielding, then use Cu foil on the backside of the end plate.
Best
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You could just order a PCB with black solder mask and the right cut outs and silkscreen text on it. Not as nice but much more accessible.
That's not difficult considering I already have a DXF for the outline, and can use that as the board outline in Altium, and just then need to add the cutout holes and silkscreen. Could even go a step further and use soldermask keep-out regions for the text instead of silkscreen.
We just 3D print the end plates and can add text as needed (don't have a Laser or CNC). If you need E-Field shielding, then use Cu foil on the backside of the end plate.
Best
I haven't even begun any level of EMI precompliance despite having half the equipment I need. I suspect the E-field shielding won't be nessesary. However, Andreas did post an interesting find on the Metrology forum, where using Wi-Fi on his datalogging computer caused a jump in dut STD-Dev. When using ethernet, the results went back to normal.
I was going to use an antenna and try and blast the DUT with varying frequency radiation first to see if I see similar behaviors, or if the metal shell sufficiently attenuates interference. My only worry is that the Hammond cases use a plastic spacer between the shell and the end plates, which is unshielded. A solution is to place the end plate behind the spacer like my initial photos showed.
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Hi,
https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6362794/#msg6362794 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6362794/#msg6362794)
This belongs here...
As I mentioned there, nothing has changed since last night; I just wanted to briefly connect the reference to check if the measurement connections were good.
The U1 chip is completely destroyed, and it also “took out” parts of the layout in the process.
I removed it and set the jumper to ext 15V—the reference itself still works... :phew:
So the question remains: what caused the chip to burn out....
It can’t be a power surge, because the batteries deliver just under 19V at no load, so I was still below the 20V maximum input voltage.
I’ll take a look at the datasheet; maybe there’s a note there regarding the design.
We should figure this out, just in case it’s a fundamental issue that could keep happening.
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Possibly the cable inductance ringing with the input capacitance? Can cause big spikes when there's no damping (e.g. you only have ceramic caps at the input with very low ESR). There's some app notes about it from linear tech.
I do see an electrolytic there though, is that across the input? Typically that would be enough to fix it, maybe it's also a super low ESR type?
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Hi,
https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6362794/#msg6362794 (https://www.eevblog.com/forum/testgear/bench-dmm-stability-comparisons-with-testcontroller/msg6362794/#msg6362794)
This belongs here...
As I mentioned there, nothing has changed since last night; I just wanted to briefly connect the reference to check if the measurement connections were good.
The U1 chip is completely destroyed, and it also “took out” parts of the layout in the process.
I removed it and set the jumper to ext 15V—the reference itself still works... :phew:
So the question remains: what caused the chip to burn out....
It can’t be a power surge, because the batteries deliver just under 19V at no load, so I was still below the 20V maximum input voltage.
I’ll take a look at the datasheet; maybe there’s a note there regarding the design.
We should figure this out, just in case it’s a fundamental issue that could keep happening.
Yep, this is the exact issue that I have seen and have mentionned in terms of hot plugging, and have warned not to do for now. Because the input is operating near the input limit of the LT3045, as Hydron mentionned, long cables with lots of inductance will ring with the cable capacitance producing a transient waveform who's peak will easily exceed the +/- 22V input maximum for the unit, which kills the VIN.
When the chip dies, the input resistance becomes quite low, and the input current will cause the chip to burn. However, yours is the worst case I have seen yet, as all my supplies are current-limited.
Solution? Use a 0.1 - 0.5ohm series R with the input, along with a high-ESR additional tantalum capacitance or electrolytic in parallel to the 4.7uF low-esr ceramic input cap close to U1 something from 10 - 100uF electrolytic should be good enough.
The reason I have not seen this issue yet is that I connect the unit to my linear supply while OFF, and then switch on the input. I have never killed a unit like this.
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@Hydron:
The electrolytic capacitor is used to buffer the ext15V path; when the jumper is set to “internal,” it is bypassed.
Since Tyler posted a link to his schematic, I assume he doesn’t mind if I post part of it here (if he does, I’ll delete it).
I took a look at the datasheet—the chip has many internal protection mechanisms—so at first I was a bit puzzled as to what could have caused it to fail.
By now, I also think there might have been voltage spikes at the input—semiconductors don't like voltage spikes... ;)
In my case, the spikes were likely caused by the circuit being closed (alligator clip connected to the battery terminal), but such spikes can also be caused by switches bouncing.
Either way, an appropriate protective measure should be added; in the simplest case, this would be a suppressor diode.
Edit:
Ah, Tyler answered..
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@Hydron:
The electrolytic capacitor is used to buffer the ext15V path; when the jumper is set to “internal,” it is bypassed.
Since Tyler posted a link to his schematic, I assume he doesn’t mind if I post part of it here (if he does, I’ll delete it).
I took a look at the datasheet—the chip has many internal protection mechanisms—so at first I was a bit puzzled as to what could have caused it to fail.
By now, I also think there might have been voltage spikes at the input—semiconductors don't like voltage spikes... ;)
In my case, the spikes were likely caused by the circuit being closed (alligator clip connected to the battery terminal), but such spikes can also be caused by switches bouncing.
Either way, an appropriate protective measure should be added; in the simplest case, this would be a suppressor diode.
Edit:
Ah, Tyler answered..
TVS could work, but given the clamping voltage / reverse working voltage window being quite small (clamp at maximum of 20V input, VRWM at 19V?), I have had a lot of difficulty finding parts that would work, and be in stock. Note that a maximum of +/-22V is the "absolute limit" for the part. Other sample schematics use the aforementionned R + C input protection rather than a diode, although the "ideal" application schematic won't include this in the LT3045 datasheet.
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Electrolytic across the input might be enough (maybe you can jumper things to put that 47uF electro onto the cable input?). Definitely sounds like the cause was what I posted.
Found the LT app note I was thinking of, worth a read: https://www.analog.com/media/en/technical-documentation/application-notes/an88f.pdf (https://www.analog.com/media/en/technical-documentation/application-notes/an88f.pdf)
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Electrolytic across the input might be enough (maybe you can jumper things to put that 47uF electro onto the cable input?). Definitely sounds like the cause was what I posted.
Found the LT app note I was thinking of, worth a read: https://www.analog.com/media/en/technical-documentation/application-notes/an88f.pdf (https://www.analog.com/media/en/technical-documentation/application-notes/an88f.pdf)
a 47uF on the cable input would be easy, as you'd unscrew the terminals a bit and then clamp the terminals of an electrolytic there. While that's a bit of a bodge fix, it may work well.
I will have to order some chips and try to kill them while implementing my fixes and see if they are really working.
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In a pinch, consider added a shunt zener and a small current PTZ fuse in series with the DC + Input. Use a leaded fuse from the + terminal with a leaded 20V Zener across the PCB input side to the - terminal. Somewhat of a bodge, but should suffice until a new design is forthcoming.
We have a few 24VDC wall switchers and a 24VDC linear type for reference use, that have a similar plug to the 12VDC switchers (an accident waiting to happen). We utilize these with some of our LM399 and LTZ1000 references, and other fixtures. If you are going for a redesign of this reference module and offering it for sale to others, consider using a linear pre regulator in front of everything else (along with PMOS type reverse voltage protection). For example a simple LM7818 or LM7820 pre regulator will withstand over 30VDC input.
Many folks will be utilizing batteries for the power source when doing reference noise measurements, and could easily add a couple 12V Lead Acid types for power, or 5 or 6 Lithium cells, the design should be able to handle this without issue.
Best
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In a pinch, consider added a shunt zener and a small current PTZ fuse in series with the DC + Input. Use a leaded fuse from the + terminal with a leaded 20V Zener across the PCB input side to the - terminal. Somewhat of a bodge, but should suffice until a new design is forthcoming.
We have a few 24VDC wall switchers and a 24VDC linear type for reference use, that have a similar plug to the 12VDC switchers (an accident waiting to happen). We utilize these with some of our LM399 and LTZ1000 references, and other fixtures. If you are going for a redesign of this reference module and offering it for sale to others, consider using a linear pre regulator in front of everything else (along with PMOS type reverse voltage protection). For example a simple LM7818 or LM7820 pre regulator will withstand over 30VDC input.
Many folks will be utilizing batteries for the power source when doing reference noise measurements, and could easily add a couple 12V Lead Acid types for power, or 5 or 6 Lithium cells, the design should be able to handle this without issue.
Best
I will likely redesign with an LT3055 instead of the '45, as the LT3055 can handle a 40V maximum input. The shunt zener is not a bad idea regardless, I may steal this idea in a redesign, and add a socketed fuse to protect against these situations. For the time being, an LM7818 would be a great solution to use a 24V input with, and provide some pre-regulation to the device. This could be implemented as a quick inline module to the existing banana plugs to avoid extra heat in the enclosure. This would be great with an 18650 pack, or some lead-acid 12V or 6V cells for long-term low noise testing.
This said, I do not plan on selling these modules readily:
A.) There is too much cost and time involved to make the product worthwhile to a hobbyist I would think. This is even before I make any profit.
B.) There is too much liability involved with selling things around here should things ever go sideways with the product.
I have no problem sending units and building them if people accept the risk of the HW being in early stages, but I don't plan to do much beyond that.
Tyler
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This said, I do not plan on selling these modules readily
Especially since there is already a commercial model available: the ADR1399 reference from Circuit Valley.
Speaking of which, the input circuitry of the Circuit Valley model includes an LT3042 along with a 22µF electrolytic capacitor at the input.
(https://www.eevblog.com/forum/projects/udr1399-adr1399-based-10v-reference-module/?action=dlattach;attach=2927550;image)
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I will likely redesign with an LT3055 instead of the '45, as the LT3055 can handle a 40V maximum input. The shunt zener is not a bad idea regardless, I may steal this idea in a redesign, and add a socketed fuse to protect against these situations. For the time being, an LM7818 would be a great solution to use a 24V input with, and provide some pre-regulation to the device. This could be implemented as a quick inline module to the existing banana plugs to avoid extra heat in the enclosure. This would be great with an 18650 pack, or some lead-acid 12V or 6V cells for long-term low noise testing.
This said, I do not plan on selling these modules readily:
A.) There is too much cost and time involved to make the product worthwhile to a hobbyist I would think. This is even before I make any profit.
B.) There is too much liability involved with selling things around here should things ever go sideways with the product.
I have no problem sending units and building them if people accept the risk of the HW being in early stages, but I don't plan to do much beyond that.
Tyler
Some of the reasons we don't sell any of our developments, personally too risky!! Altho one can get a "donation" without any risk nor implied "warranty", which seems a good path forward.
If you are rolling a new updated PCB consider a PMOS reverse polarity protector, it doesn't drop any significant forward voltage in normal operation.
Best
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This said, I do not plan on selling these modules readily
Especially since there is already a commercial model available: the ADR1399 reference from Circuit Valley.
Speaking of which, the input circuitry of the Circuit Valley model includes an LT3042 along with a 22µF electrolytic capacitor at the input.
(https://www.eevblog.com/forum/projects/udr1399-adr1399-based-10v-reference-module/?action=dlattach;attach=2927550;image)
The point of my unit, was to add some "features" to the existing CV version, which have been discussed at length on the metrology forum for extracting the best performance out of the ADR1399. Having built a rev1 unit in the same manner as the CV version, I wasn't pleased with the TC drift of using individual resistors, which is why I moved to a buried and matched network.
The bootstrapped zener was merely just a test as I wished to see the influence on the output noise, which also seems to have improved over my previous version inspired by CV. Equally, an output transistor for higher current output was nice, as I can now load the output significantly more than when only using the buffer amp output.
These were just some changes I wanted to prove out, and features that I wanted on the CV units, to try and extract the maximum stability from the reference.
I will likely redesign with an LT3055 instead of the '45, as the LT3055 can handle a 40V maximum input. The shunt zener is not a bad idea regardless, I may steal this idea in a redesign, and add a socketed fuse to protect against these situations. For the time being, an LM7818 would be a great solution to use a 24V input with, and provide some pre-regulation to the device. This could be implemented as a quick inline module to the existing banana plugs to avoid extra heat in the enclosure. This would be great with an 18650 pack, or some lead-acid 12V or 6V cells for long-term low noise testing.
This said, I do not plan on selling these modules readily:
A.) There is too much cost and time involved to make the product worthwhile to a hobbyist I would think. This is even before I make any profit.
B.) There is too much liability involved with selling things around here should things ever go sideways with the product.
I have no problem sending units and building them if people accept the risk of the HW being in early stages, but I don't plan to do much beyond that.
Tyler
Some of the reasons we don't sell any of our developments, personally too risky!! Altho one can get a "donation" without any risk nor implied "warranty", which seems a good path forward.
If you are rolling a new updated PCB consider a PMOS reverse polarity protector, it doesn't drop any significant forward voltage in normal operation.
Best
The PMOS RV protection is a good idea, I shipped Josh an inline OV, UV, RV protection module that had these features using the LTC4368. I quite liked that part, and would certainly use one in the future when integrating the design into a potential future revision.
Tyler
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..would not be a 7815 or a similar jelly-bean (with a serial zener in front of it when with an input voltage >35V) enough for the ADR1399??
The usage of those LT30xx looks like gold-plating to me.. :D
PS: I would place the linear voltage regulator off the main pcb (the pcb with the 1399 and 7->10V divider resistors on it) as the heat loss it creates depends on the input voltage in case of the batteries as well as a varying mains voltage.
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The ADR1399 should not need a special low noise supply. If at all it would be the heater part that wants a stable supply. The zener part is bootstrapped anyway and the OP-amps have a pretty good PSRR.
A 7815 is not ideal, because of the rather large drop out voltage. If really concerned with the noise for the heater, one could also use an OP-amp as driver and derive the voltage from the refenrence. Something like a TLV9301 should be sufficient.
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..would not be a 7815 or a similar jelly-bean (with a serial zener in front of it when with an input voltage >35V) enough for the ADR1399??
The usage of those LT30xx looks like gold-plating to me.. :D
PS: I would place the linear voltage regulator off the main pcb (the pcb with the 1399 and 7->10V divider resistors on it) as the heat loss it creates depends on the input voltage in case of the batteries as well as a varying mains voltage.
When the power mux on the board is selected as supplying the 15V rail with an external 15V source, this is more than possible, and an external regulator or power supply may be used. The extra heat source in proximity to the zener and gain stage components was ill-advised, so this is why I added this option. Putting the regulator in an external enclosure attached through short leads to the main ref isn't difficult.
However, I didn't have a low noise power supply at the time, so the LT30xx seemed like a fair decision, although it could certainly be a cheaper linear regulator.