Author Topic: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x  (Read 134416 times)

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Offline Alex Nikitin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #175 on: November 11, 2016, 02:12:33 pm »
Short answer: the voltage never settles upwards.

And what happens if you connect both sides (one as a zener, one as a diode in series with zener)?

Cheers

Alex

I am not sure what you are asking to try. Maybe draw it out by hand and post the drawing(s)?

Like that:

Cheers

Alex
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #176 on: November 11, 2016, 03:00:48 pm »
Short answer: the voltage never settles upwards.

And what happens if you connect both sides (one as a zener, one as a diode in series with zener)?

Cheers

Alex

I am not sure what you are asking to try. Maybe draw it out by hand and post the drawing(s)?

Like that:

Cheers

Alex

I believe that is how it is connected and is how it is intended to be used. Pin 1 is the red dot which is the output. Pin 2 is grounded. Pin 3 is the case is ignored.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 
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Offline Alex Nikitin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #177 on: November 11, 2016, 03:07:11 pm »
I believe that is how it is connected and is how it is intended to be used. Pin 1 is the red dot which is the output. Pin 2 is grounded. Pin 3 is the case is ignored.

OK, thanks, that was my understanding as well, however from the discussion in this thread it was not quite clear.

Cheers

Alex
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #178 on: November 11, 2016, 04:58:29 pm »
For manual finding the optimum current, one could look an the stabilization curve (the first 10-20 seconds or so) after turning the current on. For too low a current, the voltage should drift down on settling and for to high a current the settling should be upwards.
Of cause one can do the same with the SMU and PC as well.

As heater one could use the second zener as well, so the observed voltage will stay about the same and one could use an AC coupled amplifier to watch small changes.

The much better performance at 10 mA suggests that the wandering / drift was due to thermal effects and 10 mA being much closer to the point of zero TC. Only 6 ┬ÁV suggests this is already rather close - e.g. a TC of a few ppm / K at most. Final performance can also depend slightly on the resistor to set the current and the environment temperature range.

It appears to be the opposite of your hypothesis.
For too-high current, the voltage drifts down. For too-low current, the voltage drifts up.

Now that that is sorted out, the zero T-C current for this device is between 7mA and 8mA in open air.  Covered in tissues the zero T-C current is between 6mA and 7mA.

That's better!
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #179 on: November 11, 2016, 05:44:25 pm »
An 6-8 mA current for zero TC sounds very good. However the optimum current seems to be quite temperature dependent if it already changes so much from open to air and covered.

It is interesting to see an negative TC and thus falling voltage at high current. The normal zener refs like 1N829 are the other way around with a negative TC at low currents and a positive at high currents.

It might be interesting to do full characterization with 1 or 2 samples, as this units seem to be different from the more normal western zeners and the DS does not give much information. Is the diode in forward direction reasonably normal and working as a temperature sensor ?
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #180 on: November 11, 2016, 06:06:48 pm »
I will mount a second device and take the same tests for currents causing rising and falling current. And I will have a try at measuring a single diode.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #181 on: November 11, 2016, 06:27:47 pm »
An 6-8 mA current for zero TC sounds very good. However the optimum current seems to be quite temperature dependent if it already changes so much from open to air and covered.

It is interesting to see an negative TC and thus falling voltage at high current. The normal zener refs like 1N829 are the other way around with a negative TC at low currents and a positive at high currents.

It might be interesting to do full characterization with 1 or 2 samples, as this units seem to be different from the more normal western zeners and the DS does not give much information. Is the diode in forward direction reasonably normal and working as a temperature sensor ?

A second mounted sample works exactly the same. High current causes voltage to fall. Low current causes voltage to rise.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #182 on: November 11, 2016, 11:47:11 pm »
I will mount a second device and take the same tests for currents causing rising and falling current. And I will have a try at measuring a single diode.

I mounted a device with the red dot at HI of the SMU. The device case is at LO of the SMU.

1mA of forced current creates 0.73 V. 1mA of reverse current creates -5V.

5mA creates  0.78V. -5mA creates -5.26V

I think that explains the device behavior.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline Galaxyrise

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #183 on: November 12, 2016, 01:55:24 am »

1mA of forced current creates 0.73 V. 1mA of reverse current creates -5V.

5mA creates  0.78V. -5mA creates -5.26V

I think that explains the device behavior.

 Seems to me that you're measuring a combination of temperature coefficient and dynamic resistance there, and the two measurements are not even the same difference in temperature.  I don't know how to draw any conclusions from it.
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #184 on: November 12, 2016, 02:18:34 am »

1mA of forced current creates 0.73 V. 1mA of reverse current creates -5V.

5mA creates  0.78V. -5mA creates -5.26V

I think that explains the device behavior.

 Seems to me that you're measuring a combination of temperature coefficient and dynamic resistance there, and the two measurements are not even the same difference in temperature.  I don't know how to draw any conclusions from it.

The observation is that there are two devices; a 5V zener in series with a 0.7v diode. Nothing more complicated than that.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline SvanGool

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #185 on: November 12, 2016, 08:22:39 am »
The observation is that there are two devices; a 5V zener in series with a 0.7v diode. Nothing more complicated than that.

Just for clarity, are you concluding that using the circuit of Alex in https://www.eevblog.com/forum/metrology/ultra-low-noise-reference-2dw232-2dw233-2dw23x/msg1068444/#msg1068444 or are you grounding the open midpoint and are you applying  a positive voltage > 7V, via a resistor, to the kathode of D2?

I would think that D2 is a diode, because it is as a reversed zener  in the first case. Or are we saying the same?
« Last Edit: November 12, 2016, 09:16:46 am by SvanGool »
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #186 on: November 12, 2016, 09:05:01 am »
So a low TC can be obtained with both diodes in series, as an 5.4 V zener with posistive TC  and one working as a normal diode with negative TC. At some current (about 5-10 mA) the TCs will compensate, since the TC depends on the current. For a normal diode the TC gets smaller (less negative) with more current. For this zener it seems the TC is also getting smaller (a little faster than that of the diode) at high current as the overall TC seems to turn negative on high currents.

Having the two diodes in series makes it possible to use the normal diode as a temperature sensor - for compensation of residual temperature dependence (not just linear) or a regulated temperature. With the diode as a sensor one might be able to get quantitative values for the TC at maybe 5 and 10 mA.

The rather good stability even at 10 mA for a device with compensating current near 7-8 mA suggests that even with not so perfect current the TC is quite low.

o far the reference looks very good - 2 more points to check:
1) One point is hysteresis: So is the voltage the same starting from cold or a higher temperature.
    For a test one could do a sequence like: off - 7.5 mA (optimum current) - 25 mA (to heat the device)  and than 7.5 mA again.

2) The last big question is long time stability. Here the SMU might not be good enough as a current source and this would be more like testing ready made reference units with case and possibly temperature control.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #187 on: November 13, 2016, 12:08:00 am »
So a low TC can be obtained with both diodes in series, as an 5.4 V zener with posistive TC  and one working as a normal diode with negative TC. At some current (about 5-10 mA) the TCs will compensate, since the TC depends on the current. For a normal diode the TC gets smaller (less negative) with more current. For this zener it seems the TC is also getting smaller (a little faster than that of the diode) at high current as the overall TC seems to turn negative on high currents.

Having the two diodes in series makes it possible to use the normal diode as a temperature sensor - for compensation of residual temperature dependence (not just linear) or a regulated temperature. With the diode as a sensor one might be able to get quantitative values for the TC at maybe 5 and 10 mA.

The rather good stability even at 10 mA for a device with compensating current near 7-8 mA suggests that even with not so perfect current the TC is quite low.

o far the reference looks very good - 2 more points to check:
1) One point is hysteresis: So is the voltage the same starting from cold or a higher temperature.
    For a test one could do a sequence like: off - 7.5 mA (optimum current) - 25 mA (to heat the device)  and than 7.5 mA again.

2) The last big question is long time stability. Here the SMU might not be good enough as a current source and this would be more like testing ready made reference units with case and possibly temperature control.

Forcing current with a SMU, the voltage is never stable in the bottom 3 or 4 digits. There is no way to measure hysteresis unless a very stable circuit is built and placed in an enclosure.

My opinion is that a stable circuit will require the same heroic effort that is built into a Fluke 731B. Selected and matched tempco resistors. Lots of places for mistakes to show up.

Then the reference diodes have to be aged and characterized and only the best one is good enough.

working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #188 on: November 13, 2016, 12:38:36 am »
I just had a "quick and dirty" thought about sending a fairly low noise / stable current through these somewhat easily.
If the SMUs and PSUs tend to be too noisy / erratic when sourcing current into them, maybe something simple like a "12V" vechicle battery through a series resistor would be more stable and low noise at least over time spans of minutes at a time at this low output current level.  I suppose a laptop battery pack or something like that might also work if the voltage is high enough to give some decent headroom.

Of course air current / thermal variations would have to be kept to a minimum with something like Bob Pease's "nested cardboard boxes" trick and tissue or something.
 
 

Offline technix

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #189 on: November 13, 2016, 09:50:45 am »
This week's order from factory is about to close. If you want to buy one of those please PM me.
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #190 on: November 13, 2016, 10:08:23 am »
The differential resistance on the zeners should be reasonable low. So changes in the resistors are attenuated by a factor of about current setting resistor to zener resistance. This could be something in the range of 50-100 if one assumes 6 V to set the current. So the demands on the resistors are not that extreme.

For the first tests I would not assume the zeners to be as good as high end parts like LTZ1000 or LTFLU. We would be very happy it could come close to the LM399 / LM129H. So it is about resolving changes in the 10 ppm range. Some thermal shielding and soldering to a board is likely needed - alone from thermal EMF.

The measurements from VintageNut suggest he got quite good stability with the SMU as a current source. But it can depend on the individual units and environment. A dedicated reference circuit could work as well - the demands for the current setting resistors are not that high (e.g. even 100 ppm/K thick film might be good enough), at least for the hysteresis test.

Attached is a suggested simple test circuit. Paralleling R3 to R2 could be used to temporarily increase the current. The lower diode of the ref can be used to get a rough idea of the reference temperature.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #191 on: November 13, 2016, 01:59:02 pm »
Hello Kleinstein

Can you please give some analysis of how your circuit is better or different from the circuit used by zlymex on the first page of this thread?
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #192 on: November 13, 2016, 04:14:52 pm »
The circuit I showed uses only 2 (instead of 3) resistors that need to be stable. Just to get a stable current for one ref. chip, even the second resistor does not really need to be a good one either.

The difference is also not that big - just replace D1/D3 with a resistor and you are back at the circuit from the first page.

For doing a transient / current step test, it might be an advantage that the current does not depend on the voltage of the ref chip under test, but on the other one. One can look at D2/D4 (e.g. 6.2 V) or at the sum of both references (12.4 V). If you want scaling to 10 V, it works slightly better (less sensitive to resistor drift) if you start from 12 V than starting from 6.2 V.
 

Online edavid

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #193 on: November 17, 2016, 11:06:24 pm »
Here is the translated datasheet.

Thank you for preparing this translation, but I think the listed pinout is incorrect.  For the devices I received from VintageNut, pins 1 and 2 are anodes, and pin 3 is the common cathode.

Also, I measure a resistance of ~800K between the 2 anodes.  Does anyone know why that is?
 

Offline Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #194 on: November 18, 2016, 05:52:48 am »

Thank you for preparing this translation, but I think the listed pinout is incorrect.  For the devices I received from VintageNut, pins 1 and 2 are anodes, and pin 3 is the common cathode.

Hello,

The translation corresponds to the picture from the datasheet. (first page on the thread).
Do you really measure 5.6 instead of 0.7V on the ground referenced diode when using a pull-up resistor?

With best regards

Andreas
 

Online edavid

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #195 on: November 18, 2016, 05:57:26 am »
Thank you for preparing this translation, but I think the listed pinout is incorrect.  For the devices I received from VintageNut, pins 1 and 2 are anodes, and pin 3 is the common cathode.
The translation corresponds to the picture from the datasheet. (first page on the thread).
Yes, that is also incorrect (or doesn't match the parts I received).  Very odd.

Quote
Do you really measure 5.6 instead of 0.7V on the ground referenced diode when using a pull-up resistor?
Sorry, I don't understand this question.
 

Offline Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #196 on: November 18, 2016, 06:27:25 am »
if you take the cirquit from Alex:

https://www.eevblog.com/forum/metrology/ultra-low-noise-reference-2dw232-2dw233-2dw23x/msg1068444/#msg1068444
e.g. with 15V supply and resistor = 1K

what voltage do you measure between Pin 3 (case of zener) and ground?

With best regards

Andreas
 

Offline Alex Nikitin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #197 on: November 18, 2016, 08:51:06 am »
I've measured (by a multimeter diode test only so far) one of the devices I've received and it is indeed a common cathode configuration, as shown on the attached diagram.

Cheers

Alex
 

Offline Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #198 on: November 18, 2016, 10:35:23 am »
So its more difficult to measure the chip temperature since the forward diode is not referred to GND.

With best regards

Andreas
 

Offline Alex Nikitin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #199 on: November 18, 2016, 10:52:06 am »
So its more difficult to measure the chip temperature since the forward diode is not referred to GND.

With best regards

Andreas

It will be easy in a negative reference configuration though ;) . In a positive reference the diode can still be used easily for a temperature stabilization with an external heater.

Cheers

Alex
 


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