Volt reference DIYer LTZ 10V PWM

[0.01C]

I got it from a Chinese DIYer

[Vgkid]

Do you have a schematic for that. What are the 2 covered sections. 1 is the reference, what is the other (lower one) ?

[0.01C]

Do you have a schematic for that. What are the 2 covered sections. 1 is the reference, what is the other (lower one) ?

I don't have ,  the lower one is a ferrite core cord ring

this pwm board was purchased for a eevblog member.

[Echo88]

Looks to me like the rebuild of a Datron 4910, since i see the bottom part with the 5-pole-filter but no top notch resistor-arrays like in the 5700A-PWM-DAC.

If i may ask: How much did it cost? It looks nicely made and the layout looks suitable.

[0.01C]

Looks to me like the rebuild of a Datron 4910, since i see the bottom part with the 5-pole-filter but no top notch resistor-arrays like in the 5700A-PWM-DAC.

If i may ask: How much did it cost? It looks nicely made and the layout looks suitable.

about USD158 , WIMA capacitor is second hand ,other parts are brand new.

[Echo88]

If you still have the board, could you make a few more detailed photos please? Id like to see which ICs were used and compare the board to the Datron 4910 schematic.

[picburner]

On bbs.38hot.net I found this schematic: it is not the same version of the pcb posted by 0.01C but this is inspired by the Datron 4910 also.

[Kleinstein]

That circuit looks quite different from the boards used. The PWM modulator and filter is very much like Datron 4910 including going the old way the JFETs and NE5534 - a more modern replacement would be audio grade JFET OPs. The rest looks somewhat different and strange in some places - it even looks like it might get easily unstable (at least I would expect C68 at a slightly different place - as shown it is more like a problem).  It is only the PWM generation from an µC that looks more modern - not the old style with 74HCxxx.

So the plan might be similar in intention, but looks different in the details.

[0.01C]

noise amp x10k , reading 25mVpp 

https://youtu.be/vKPXxuj6usQ

[lukier]

noise amp x10k , reading 25mVpp 

Interesting amplifier, do you have any details?

Is that based on zlymex design (0.1-10Hz, 10k gain)
https://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/
or more similar to Tek's AM502 (looks like, gains and frequency ranges)?

[0.01C]

noise amp x10k , reading 25mVpp 

Interesting amplifier, do you have any details?

Is that based on zlymex design (0.1-10Hz, 10k gain)
https://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/
or more similar to Tek's AM502 (looks like, gains and frequency ranges)?

I bought the amp. from my friend CNY300,I think it is based on lymex design.

[zhtoor]

noise amp x10k , reading 25mVpp 

Interesting amplifier, do you have any details?

Is that based on zlymex design (0.1-10Hz, 10k gain)
https://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/
or more similar to Tek's AM502 (looks like, gains and frequency ranges)?

I bought the amp. from my friend CNY300,I think it is based on lymex design.

thanks, could you point at a place where one could be bought?

regards.

[Andreas]

noise amp x10k , reading 25mVpp 

Hello,

Without putting the DUT battery supplied into a shielded environment?
Unbelievable. Where is the mains hum?

with best regards

Andreas

[0.01C]

noise amp x10k , reading 25mVpp 

Hello,

Without putting the DUT battery supplied into a shielded environment?
Unbelievable. Where is the mains hum?

with best regards

Andreas

The reading is magnified by the noise amplifier by 10k , that ltz pwm ref. noise is about 2.5uVpp

[0.01C]

noise amp x10k , reading 25mVpp 

Interesting amplifier, do you have any details?

Is that based on zlymex design (0.1-10Hz, 10k gain)
https://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/
or more similar to Tek's AM502 (looks like, gains and frequency ranges)?

I bought the amp. from my friend CNY300,I think it is based on lymex design.

thanks, could you point at a place where one could be bought?

regards.

My friend said there are still have five sets , but he needs time to welding and test, may be the end of the month to sell,

[Andreas]

The reading is magnified by the noise amplifier by 10k , that ltz pwm ref. noise is about 2.5uVpp

Mhm,

what are the H and the L LEDs for?
are they "overdrive/clipping" indicators?

Without a shielded environment and with all those switchmode supplies on the same mains outlet it is most likely that the scope is showing something wrong.

with best regards

Andreas

[lukier]

My friend said there are still have five sets , but he needs time to welding and test, may be the end of the month to sell,

Is the schematic open source? I would be keen to see how he implemented switchable frequencies and gains - this is missing from the original lymex design (fixed 0.1-10Hz, 10k gain).

[Kleinstein]

Only 2.5 µV_pp of noise is quite low.  Filtering of the supply of the reference circuit should not be that important, as there is already a DCDC converter on the board - so the supply filtering needs to be on the board anyway. If the PWM filtering is low enough it might be effective against 100 Hz ripple, maybe even 50 Hz.

The noise measurement amplifier seems to use 3 independent low pass filters und thus likely 100 kHz as the full bandwidth of the amplifier.  Normally the setup should be something like  x100  - 0.1 Hz high pass filter, maybe x 10 - low pass filters with switches  - switchable amplifier x 1 / 10 / 100 .

[0.01C]

noise amp x10k , reading 25mVpp 

Interesting amplifier, do you have any details?

Is that based on zlymex design (0.1-10Hz, 10k gain)
https://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/
or more similar to Tek's AM502 (looks like, gains and frequency ranges)?

I bought the amp. from my friend CNY300,I think it is based on lymex design.

thanks, could you point at a place where one could be bought?

regards.

Hi ,

My friend finished 4 sets today, he will placed it in Taobao for sell tomorrow, and he also want to give 5 pieces ltz pcb (pcb only) to eevblog member for free.

[lukier]

Nice!

I'm actually planning something similar - DIY Fluke 734A, that is 4 LTZ1000 based 10V reference modules, each with 10K reference as well. For now I have all the parts for the 7V reference circuit and 10K resistors (VHP202Z) and I need to design the board. Once I finish that and the references will be aging I'll have plenty of time to figure out other circuits in the module (battery + power supply/charging, 7->10V step-up, mini-oven for VHP202Z 10K maybe, small signal relay to switch output between raw 7V and 10V, output protection etc.).



He must have excellent access to parts, all the oil filled Vishays, hermetic LT1013 and so on. Many months ago I requested a quote from Vishay, as I wanted to buy the LTZ1000 resistors and 10K reference (5 sets) and I got completely ignored, so I got second hand resistors (non-oil filled Vishays for LTZ1000 and VHP202Z) from eBay and the remaining parts (including LTZ1000 and LT1013 DIP8) from DigiKey.

Interesting power/voltage connection with the bare wires soldered between the mini-module and the base board. I've decided to go the 3458A reference module route and planned pin header connectors. Are bare wires better with respect to thermal EMF?

[0.01C]

We have done several times group buy vishay resistor ,VHP101T 100R 9.998K ,VHP202 9.998K  ,VHD200T 6K3:13K8........

[0.01C]

Nice!

I'm actually planning something similar - DIY Fluke 734A, that is 4 LTZ1000 based 10V reference modules, each with 10K reference as well. For now I have all the parts for the 7V reference circuit and 10K resistors (VHP202Z) and I need to design the board. Once I finish that and the references will be aging I'll have plenty of time to figure out other circuits in the module (battery + power supply/charging, 7->10V step-up, mini-oven for VHP202Z 10K maybe, small signal relay to switch output between raw 7V and 10V, output protection etc.).



He must have excellent access to parts, all the oil filled Vishays, hermetic LT1013 and so on. Many months ago I requested a quote from Vishay, as I wanted to buy the LTZ1000 resistors and 10K reference (5 sets) and I got completely ignored, so I got second hand resistors (non-oil filled Vishays for LTZ1000 and VHP202Z) from eBay and the remaining parts (including LTZ1000 and LT1013 DIP8) from DigiKey.

Interesting power/voltage connection with the bare wires soldered between the mini-module and the base board. I've decided to go the 3458A reference module route and planned pin header connectors. Are bare wires better with respect to thermal EMF?

Do you want the 7-10 and ltz ref. PCB ?I can send you one set.

[lukier]

Do you want the 7-10 and ltz ref. PCB ?I can send you one set.

Sure, I'm planning four 10V-10K reference modules, but I have parts for 5 sets (backup) so I could build one on your PCBs first before designing my own reference mini-module. I'll PM you.

We have done several times group buy vishay resistor ,VHP101T 100R 9.998K ,VHP202 9.998K  ,VHD200T 6K3:13K8........

I think we should introduce this bbs.38hot.net tradition here at the eevblog forum So far I managed to buy some 2DW233 thanks to technix's group buy initiative.
BTW This box of Vishays is a small fortune

[0.01C]

My friend said there are still have five sets , but he needs time to welding and test, may be the end of the month to sell,

Is the schematic open source? I would be keen to see how he implemented switchable frequencies and gains - this is missing from the original lymex design (fixed 0.1-10Hz, 10k gain).

yes

[d-smes]

The reading is magnified by the noise amplifier by 10k , that ltz pwm ref. noise is about 2.5uVpp

Mhm,

what are the H and the L LEDs for?
are they "overdrive/clipping" indicators?

Without a shielded environment and with all those switchmode supplies on the same mains outlet it is most likely that the scope is showing something wrong.

with best regards

Andreas

Andreas-  You are quite right.  According to schematic, H and L LEDs are overload indicators that trigger at +/- 2.6V or so.  Since first stage gain = 100, that says input noise is >26 mV.  Assuming, of course, that noise amplifier was connected when picture was taken.