Volt reference DIYer LTZ 10V PWM  - Page 1
Forum section: electronics / general

author: 0.01C
author_rank: Regular Contributor
timestamp: July 02, 2017, 02:03:42 am
content: I got it from a Chinese DIYer

author: Vgkid
author_rank: Super Contributor
timestamp: July 02, 2017, 03:09:48 am
content: Do you have a schematic for that. What are the 2 covered sections. 1 is the reference, what is the other (lower one) ?

author: 0.01C
author_rank: Regular Contributor
timestamp: July 02, 2017, 03:23:23 am
content: Quote from: Vgkid on July 02, 2017, 03:09:48 amI don't have , the lower one is a ferrite core cord ringthis pwm board was purchased for a eevblog member.

author: Echo88
author_rank: Frequent Contributor
timestamp: July 02, 2017, 09:52:09 am
content: 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.

author: 0.01C
author_rank: Regular Contributor
timestamp: July 02, 2017, 01:15:02 pm
content: Quote from: Echo88 on July 02, 2017, 09:52:09 amabout USD158 , WIMA capacitor is second hand ,other parts are brand new.

author: Echo88
author_rank: Frequent Contributor
timestamp: July 03, 2017, 02:18:29 pm
content: 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.

author: picburner
author_rank: Frequent Contributor
timestamp: July 03, 2017, 09:49:02 pm
content: 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 04, 2017, 03:39:59 pm
content: 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.

author: 0.01C
author_rank: Regular Contributor
timestamp: July 06, 2017, 01:55:13 pm
content: noise amp x10k , reading 25mVpphttps://youtu.be/vKPXxuj6usQ

author: lukier
author_rank: Unknown
timestamp: July 06, 2017, 03:54:52 pm
content: Quote from: 0.01C on July 06, 2017, 01:55:13 pmInteresting 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)?

author: 0.01C
author_rank: Regular Contributor
timestamp: July 06, 2017, 05:00:31 pm
content: Quote from: lukier on July 06, 2017, 03:54:52 pmI bought the amp. from my friend CNY300,I think it is based on lymex design.

author: zhtoor
author_rank: Frequent Contributor
timestamp: July 06, 2017, 05:59:22 pm
content: Quote from: 0.01C on July 06, 2017, 05:00:31 pmthanks, could you point at a place where one could be bought?regards.

author: Andreas
author_rank: Super Contributor
timestamp: July 06, 2017, 09:46:13 pm
content: Quote from: 0.01C on July 06, 2017, 01:55:13 pmHello,Without putting the DUT battery supplied into a shielded environment?Unbelievable. Where is the mains hum?with best regardsAndreas

author: 0.01C
author_rank: Regular Contributor
timestamp: July 07, 2017, 01:46:58 am
content: Quote from: Andreas on July 06, 2017, 09:46:13 pmThe reading is magnified by the noise amplifier by 10k , that ltz pwm ref. noise is about 2.5uVpp

author: 0.01C
author_rank: Regular Contributor
timestamp: July 07, 2017, 01:53:51 am
content: Quote from: zhtoor on July 06, 2017, 05:59:22 pmMy 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,

author: Andreas
author_rank: Super Contributor
timestamp: July 07, 2017, 06:20:34 am
content: Quote from: 0.01C on July 07, 2017, 01:46:58 amMhm,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 regardsAndreas

author: lukier
author_rank: Unknown
timestamp: July 07, 2017, 06:25:49 am
content: Quote from: 0.01C on July 07, 2017, 01:53:51 amIs 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).

author: Kleinstein
author_rank: Super Contributor
timestamp: July 07, 2017, 07:06:55 am
content: 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 .

author: 0.01C
author_rank: Regular Contributor
timestamp: July 07, 2017, 04:03:44 pm
content: Quote from: zhtoor on July 06, 2017, 05:59:22 pmHi ,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.

author: lukier
author_rank: Unknown
timestamp: July 07, 2017, 04:22:39 pm
content: 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?

author: 0.01C
author_rank: Regular Contributor
timestamp: July 07, 2017, 04:42:08 pm
content: We have done several times group buy vishay resistor ,VHP101T 100R 9.998K ,VHP202 9.998K ,VHD200T 6K3:13K8........

author: 0.01C
author_rank: Regular Contributor
timestamp: July 07, 2017, 04:50:01 pm
content: Quote from: lukier on July 07, 2017, 04:22:39 pmDo you want the 7-10 and ltz ref. PCB ?I can send you one set.

author: lukier
author_rank: Unknown
timestamp: July 07, 2017, 04:57:12 pm
content: Quote from: 0.01C on July 07, 2017, 04:50:01 pmSure, 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.Quote from: 0.01C on July 07, 2017, 04:42:08 pmI think we should introduce this bbs.38hot.net tradition here at the eevblog forumSo far I managed to buy some 2DW233 thanks to technix's group buy initiative.BTW This box of Vishays is a small fortune

author: 0.01C
author_rank: Regular Contributor
timestamp: July 08, 2017, 05:17:25 am
content: Quote from: lukier on July 07, 2017, 06:25:49 amyes

author: d-smes
author_rank: Regular Contributor
timestamp: July 08, 2017, 10:08:20 pm
content: Quote from: Andreas on July 07, 2017, 06:20:34 amAndreas- 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.

author: Andreas
author_rank: Super Contributor
timestamp: July 09, 2017, 04:06:51 am
content: Quote from: d-smes on July 08, 2017, 10:08:20 pmThat question is answered in the video.(don´t know wether the "Lab" supply for the reference is also a switchmode supply).with best regardsAndreas

author: Kleinstein
author_rank: Super Contributor
timestamp: July 09, 2017, 08:17:45 am
content: The LED circuit shown is odd: The LED would turn off if the signal gets close to saturation. Normally both LEDs would be on.So both LEDs on is OK, but hard to tell (especially from a photo) if there is some clipping.With only 25 mV at the output I would not expect clipping.

author: 0.01C
author_rank: Regular Contributor
timestamp: July 11, 2017, 06:58:33 am
content: Today I received LTZ1000 Ref. pcb and 2DW232 (date code 15-4),noise meter is on the way.

author: 0.01C
author_rank: Regular Contributor
timestamp: July 11, 2017, 07:18:41 am
content: Quote from: lukier on July 07, 2017, 04:57:12 pmwhat is the date code of your 2DW232?what color of the ltz cover you like?

author: lukier
author_rank: Unknown
timestamp: July 11, 2017, 08:26:22 am
content: Quote from: 0.01C on July 11, 2017, 07:18:41 amHmm, no date code on the package. Just factory logo and 2DW233. Yellow painted dot on the side (see picture).Quote from: 0.01C on July 11, 2017, 07:18:41 amDoesn't matterIf you are short on covers don't worry, I have a 3D printer so I can print it.

author: 0.01C
author_rank: Regular Contributor
timestamp: July 11, 2017, 08:36:23 am
content: Quote from: lukier on July 11, 2017, 08:26:22 amno date code ?

author: tszaboo
author_rank: Super Contributor
timestamp: July 11, 2017, 08:59:22 am
content: I was sending a similar PWM + LTZ1000 reference into production once. Though the application was different, I needed stable 5V from the 7.2 instead of 10, but the principle is very similar.I'm missing something from all these schematic, which was very important in my experience. R30 and R31 (from the PWM10V1 schematic) has to be low tempco, big physically, and special care has to be done for the routing. C44 and C45 also. Foil capacitors to start with, with as small leakage as possible. Otherwise there will be problems, like leakage shifting the output, and the like. I even put a leakage guard trace (driven by a whatever opamp) below C44 and C45, protecting that entire node. All leakage gets multiplied by 100KOhm so thats why.Otherwise the circuit is... a copycat. Not doing judgement, but there are better opamps available than back then. Also, the JFET switches

author: 0.01C
author_rank: Regular Contributor
timestamp: July 11, 2017, 11:31:43 am
content: 4 noise meter just arrival

author: 0.01C
author_rank: Regular Contributor
timestamp: July 15, 2017, 05:40:05 am
content: All 10V LTZ PWM reference and noise meter has been sent, I hope they enjoy, I also sent some different date code of 2dw to a member for test and comparison.

author: 0.01C
author_rank: Regular Contributor
timestamp: July 22, 2017, 01:10:33 am
content: @Charlie Beuning USAMy friend contact me today said you have bought a noise meter from his taobao shop ,but there is no stock now ,please pm me,Thanks