PX Reference

[hwj-d]

Let's see, the noisefloor comes out with this LT1763 board. I'm building a little PS with mains-filtering and 2x200mA Blocktrafo for two LT1763.

[eurofox]

I got my 1st one ready, output 7.0666V on my Brymen BM869S, I just sold my Agilent 34401A and wait for my Keithley 2001 for more accurate data.

Just surprised with low voltages, usually is in the area of 7.1V

Next one will be with resistors from Edwin Pettis.

eurofox

[Dr. Frank]

I got my 1st one ready, output 7.0666V on my Brymen BM869S, I just sold my Agilent 34401A and wait for my Keithley 2001 for more accurate data.

Just surprised with low voltages, usually is in the area of 7.1V

Next one will be with resistors from Edwin Pettis.

eurofox

Beneath sample variation, that depends also on the oven temperature.
Maybe you have used 15k/1k?

Frank

[eurofox]

I got my 1st one ready, output 7.0666V on my Brymen BM869S, I just sold my Agilent 34401A and wait for my Keithley 2001 for more accurate data.

Just surprised with low voltages, usually is in the area of 7.1V

Next one will be with resistors from Edwin Pettis.

eurofox

Beneath sample variation, that depends also on the oven temperature.
Maybe you have used 15k/1k?

Frank

Hello Frank,

I got 12K2955/1K, it should be a little bit higher than with a 13K 

eurofox

[hwj-d]

Hello Dr. Frank,

for what is this temp-resistor between the two primary 110V windings in your block-transformer? Is it necessary to use one, and what type is it?

Thanks

[cellularmitosis]

I got 12K2955/1K, it should be a little bit higher than with a 13K 

No worries, the two boards which I have assembled so far are both using 12k2 /  1k dividers from the ebay hifi seller.  They seem fine in a less-than-72F environment so far.

[Dr. Frank]

Hello Dr. Frank,

for what is this temp-resistor between the two primary 110V windings in your block-transformer? Is it necessary to use one, and what type is it?

Thanks

You're  referring to my Precision Current Source article?
That's been in the EAGLE lib only, it's a principle circuit diagram.
These BLOCK transformers sometimes have a thermal safety fuse (resettable) inside, though.

Frank

[hwj-d]

Hello Dr. Frank,

for what is this temp-resistor between the two primary 110V windings in your block-transformer? Is it necessary to use one, and what type is it?

Thanks

You're  referring to my Precision Current Source article?

Yes. Forgot the thread in the moment.

That's been in the EAGLE lib only, it's a principle circuit diagram.
These BLOCK transformers sometimes have a thermal safety fuse (resettable) inside, though.

Frank

Many thanks. Then I don't need it explicitly.

[Andreas]

I got 12K2955/1K, it should be a little bit higher than with a 13K 

eurofox

Hello,
I think it is the other way round:
The raw TC of the zener is around 50 ppm/K.
with 12K3 against 13K you lower the setpoint by around 14 deg C giving -700 ppm or around -5mV against nominal.

with best regards

Andreas

[hwj-d]

New kids on the block

Build two little gem's with PX V2.4 and TEKO 371 54 x 50 x 26 mm

The pictures says it all:





The resistors i've used:





Thanks to cellular 

[hwj-d]

Some more pictures:







Size comparison:

[hwj-d]

Some measurements: these are also very stable.

[Echo88]

Nice! I particularly like the close thermal coupling of the divider-resistors.

[TiN]

Cute. However hanging binding posts are asking for a trouble  .
Also to apply term "very stable" to LTZ ref, one need use better measurement gear and talk about this after at least few months of ageing  .

[hwj-d]

Hello TiN,

yes, that's right. i know it all. 

Shurely, the cuties are not there to be used with binding posts in this way, but to be used in another housing because of additionally RF shielding. That's an experiment at all.

Also, term "very stable" should mean for this early measuring of course. Maybe I should have expressed myself more cautious, but in the meantime we all know what we have from these ltz's on one or the other kind of this pcb's and costs and effort of them.

[cellularmitosis]

I love it!  Great job hwj-d.  I have some TEKO cases on their way

Have you toyed with the temperature compensation resistor yet (400k)?  I’m waiting on more thermal epoxy to arrive before I can take another shot at making a heated enclosure.

You might try measuring two LTZ’s back-to-back, which will give you more resolution.  Connect the positive output of two refs to the inputs of your meter, then bridge the two negative outputs together.

Edit: Andreas mentioned using isolated supplies for this measurement.

[hwj-d]

I love it!  Great job hwj-d.  I have some TEKO cases on their way

 

But one little caveat are there with my solder posts and TEKO 371. Because they are interference fittings, I can't get out the pcb without destroying two of them (maybe not, i've not tried it yet).

Have you toyed with the temperature compensation resistor yet (400k)?  I’m waiting on more thermal epoxy to arrive before I can take another shot at making a heated enclosure.

No, that's one urgent next point to learn for me. Next step is to build this 2*200mA psu as compact as possible. Then bring it together with temp compensation, output other voltages, maybe multiples, and so on.

What's about a kj7e's 10V buffer pcb from osh? 
(€: no, first, need to play arround with own measuring values, LTC2057, and so on, with respect to kj7e's suggestions.  )

I think, TiN and others are right. The measuring possibilities reach their limit with lm399 based instruments. Now I need a K7510...  unattainable ...

You might try measuring two LTZ’s back-to-back, which will give you more resolution.  Connect the positive output of two refs to the inputs of your meter, then bridge the two negative outputs together.

Edit: Andreas mentioned using isolated supplies for this measurement.

Yes absolutely. A big playground opens up. 

[hwj-d]

After burn in a couple of weeks, i need a calibration of one or some of them.
(as free as possible, except shipping costs of course.  )
Who can I address then, medium term, if possible in Germany or EU?
I know, maybe a difficult question...

Thanks

[Echo88]

You can ship it to me: I have a 3458A, last calibrated about 9 Months ago. Other users in Germany with a 3458A are Dr. Frank, Andreas, e61_phil and High Voltage (if memory serves me right).

[splin]

Some measurements: these are also very stable.

Min:+ 7.124 16,  Max:+ 7.124 18, Span: 0.000 01?

[cellularmitosis]

Oh, I just noticed that 7.12417 is repeated twice on the vertical scale.  What is the vertical scale of that graph?

[hwj-d]

You can ship it to me: I have a 3458A, last calibrated about 9 Months ago. Other users in Germany with a 3458A are Dr. Frank, Andreas, e61_phil and High Voltage (if memory serves me right).

That's very sweet of you! Thanks. 

After a couple of weeks burn in, I would like to use that, after PM.

Big, big thanks again

[hwj-d]

@splin,

there is a small peak, going to Max:+ 7.124 18, that's not going to span, luckily.

@cellular,

yes, that's often criticized indistinctness from many people to Keysight.

But look at the average, that's says 7.124 166 above the middle line, that is 7.124 165 (wrong) roundet to 7.124 17. The whole y-achsis is 10µV, so the lower is 7.124 16 the upper is real 7.124 17. 

[hwj-d]

The other measurement picture seems to be even more opaque. 

Average says 7.153 564V. The y-scale span is again 10µV.

Now the upper line is (wrong, at this point) roundet to 7.153 57 but real 7.153 565.
The middle line is real 7.153 560,
and the lower line is real 7.153 555, but again wrong roundet to 7.153 56

 

[splin]

@splin,

there is a small peak, going to Max:+ 7.124 18, that's not going to span, luckily.

I assume this comes from rounding issues - using 7 1/2 digits internally, but only displaying 6 1/2. One of the reasons that some prefer to use the DMM for datalogging and using a spreadsheet for the statistics calculations so you know exactly what is going on.