Group buy: LTZ1000A precision resistor set (Econistor 8G16 precision wirewound)

[jfedison741]

Hello,
Just trying to find out if there may be interest in a group buy for precision resistor sets needed to build the LTZ1000A board by Dr. Frank. These would be coming from General Resistor (parent company http://www.primetechnology.com/).

The resistor set would consist of the following (suitable for the LTZ1000A version providing a heater set point of ~ 52°C):

Ref Des  Qty  Part Number

R1         1     8G16D120R
R2,R3    2     8G16D70K
R4         1     8G16D12K5
R5         1     8G16D1K

According to the datasheet (http://primetechnology.com/cp/images/PartsDocument/163323.pdf) these resistors are specified for +/- 0.1% accuracy,  +/- 35ppm/yr stability,  and +/- 5ppm/°C (max) tempco.

This is the pricing I currently have (USD):
8G16D120R                        10 – 49 pieces    $7.08 each
8G16D70K                          10 – 49 pieces    $6.17 each
8G16D12K5                        10 – 49 pieces    $7.38 each
8G16D1K                            10 – 49 pieces    $5.09 each

So total cost (R1-R5): $31.89 + tax + shipping

General Resistor is indicating 6 weeks delivery time (so arrival week of Nov 16 or after depending on when the group order is placed).

At this time, I intend to restrict this group buy to USA addresses only. If you are interested in this group buy, please send me a PM and indicate how many sets you would like. If we have enough interest for at least 10 sets, I will place an order. Once they arrive, I will notify the group and will collect your payment & shipping address individually. I plan to ship using FedEx ground. By Oct. 16 I will update this thread on whether we have met the 10 set minimum.

Please let me know if you have any questions.

Jeff

[mawyatt]

I've designed a couple precision references for my home use. One is based around the LM399 and a standard IC reference (REF01) and has 10V, 1V and 0.1V outputs, the other has a LTZ1000 and LM399 as well as a IC reference and has 7V(Vz) & 10V outputs. The PCBs were designed for the Vishay/Dale resistors as well as 0805 & 0603 Surface Mount resistors.

The General Resistor 8G16D appears to be too long to fit, so would need to be vertically mounted. The Miniohm (5G10) and Squaristor (GG102) are smaller and might fit the PCB.

Have you considered the smaller footprint resistors, are they more expensive?

BTW Both PCBs work very well, I have all the components for the LTZ1000 section of the PCB except I forgot to order (which I need to do) the LT recommended Op-Amp

Best,

[jfedison741]

The General Resistor 8G16D appears to be too long to fit, so would need to be vertically mounted. The Miniohm (5G10) and Squaristor (GG102) are smaller and might fit the PCB.

Have you considered the smaller footprint resistors, are they more expensive?

I like the 8G16D because they have typical performance specs that appear to be very good as far as moisture and other conditions, typically 10 to 35 ppm stability across the various test conditions. The SMT precision resistors that I have seen (e.g. Vishay VSMP or Susumu RG) generally have worse stability in the range of 100 - 200 ppm for VSMP or 100 - 500 ppm for RG. Thermal emf is also specified for 8G16D (1.5 uV/°C typical) but I have not seen this defined in the spec for either VSMP or RG. At 10 piece quantities VSMP price looks comparable to that of 8G16D. I have not looked into 5G10 or GG102. My main goal is to use something that has good stability and has compatible footprint with the Dr. Frank board (8G16D are the original green resistors used in the first builds of that board).

BTW, those are very spiffy looking reference boards.

[mawyatt]

The General Resistor 8G16D appears to be too long to fit, so would need to be vertically mounted. The Miniohm (5G10) and Squaristor (GG102) are smaller and might fit the PCB.

Have you considered the smaller footprint resistors, are they more expensive?

I like the 8G16D because they have typical performance specs that appear to be very good as far as moisture and other conditions, typically 10 to 35 ppm stability across the various test conditions. The SMT precision resistors that I have seen (e.g. Vishay VSMP or Susumu RG) generally have worse stability in the range of 100 - 200 ppm for VSMP or 100 - 500 ppm for RG. Thermal emf is also specified for 8G16D (1.5 uV/°C typical) but I have not seen this defined in the spec for either VSMP or RG. At 10 piece quantities VSMP price looks comparable to that of 8G16D. I have not looked into 5G10 or GG102. My main goal is to use something that has good stability and has compatible footprint with the Dr. Frank board (8G16D are the original green resistors used in the first builds of that board).

BTW, those are very spiffy looking reference boards.

Agree the 8G16D do have a full range of specs that others don't and being a wire wound I believe, probably a better resistor for the LTZ1000.

The PCBs were designed to be used (without the terminals) with this enclosure. I don't have the enclosures yet, they are apparently out of stock.

https://www.ebay.com/itm/142615126986

These PCBs allow the LM399 & LTZ1000 to be compared, and also support a few different SOIC 8 packaged references, and allow all sorts of various resistors, capacitors and ICs to be used. The black board has 1V and 0.1V outputs using a CMOS Autozero Op-Amp to help with DVM calibration, but does not support the LTZ1000.

Also have some direct plug in devices for helping check DVMs, the blue one has a precision AC waveform. All the PCBs have a thermistor for temp checking, some have capability for 2 or 3 types.


Best,

[jfedison741]

Just an update:
For anyone outside United States and wanting to be part of this group buy, I just learned about a service called myus.com which will allow you to specify a US shipping address for your order and then myus.com will forward ship your order to your international address.

Right now there are a total of 5 resistor sets reserved and we need at least another 5 in order to meet the 10 part limit (and the USD250 min order from General Resistance).

[AlfBaz]

Just an update:
For anyone outside United States and wanting to be part of this group buy, I just learned about a service called myus.com which will allow you to specify a US shipping address for your order and then myus.com will forward ship your order to your international address.

Right now there are a total of 5 resistor sets reserved and we need at least another 5 in order to meet the 10 part limit (and the USD250 min order from General Resistance).

Any reason you cant just send them in a padded envelope with tracking via normal post?

[felixd]

Hey @mawyatt. What banana plugs are You using?

[mawyatt]

Got these off eBay, no part number tho. Supposedly they are gold plated copper.

Best,

[jfedison741]

Any reason you cant just send them in a padded envelope with tracking via normal post?

I haven't looked into what is needed for international shipping and I would like to simplify my shipping task. The myus.com service is available for addresses outside the US.

[maginnovision]

What is tax for you?

[alanambrose]

>>> Any reason you cant just send them in a padded envelope with tracking via normal post?

USPS? That option would work too. A bit slow delivery-wise, but nevertheless. From memory, it means filling in a tiny stick-on label with value and description and that's it. All the customs charging etc happens at the receiver's end.

Alan

[Edwin G. Pettis]

I used to ship resistors in envelopes but I had several shipments mangled by mostly foreign postal services, resistors were literally crushed so I use 200LB test boxes now and haven't lost an order yet, they do cost slightly more than an envelope but the hassle with postal insurance usually isn't worth the trouble.  Mind you, it isn't that easy to break resistor bodies, I don't know what actually caused the damage but it definitely took some effort.

Ultrohm Plus

[ramon]

Is there anything wrong with USPS FCPIS®?

[branadic]

People from Europe can order General Resistance 8G16 Econistor Series at RhopointComponents if they don't want to hazzle with import taxes.

-branadic-

[dietert1]

Last year i bought at rhopointcomponents.com and later found that those resistors were somewhat unstable under humidity (about 100 ppm changes seen). I should have five complete sets that i won't use. One set has 120R, 1K, 12K, 2x 70K, 4K7, 10K (all 8G16D, +/- 0,1 %, +/- 5 ppm/K). Last two were meant for amplifier 7 => 10V. If somebody in Germany or EU wants a set, will offer at half price plus postage, please communicate.

Regards, Dieter

Edit about the mentioned humidity test:
That was a very naive test i did when those econistors arrived in June 2019. We have several kg of desiccant for our 3D printer  and i prepared a bag and put one of those resistors inside. Within two weeks there was a 220 ppm change and i stopped watching. So that was a humidity change from 30 or 40 %  down to about 5 or 10 % RH. Repeated the test with another one, similar result. Then i checked an UPW50 and its shift was several times slower. Its enclosure seems to be better, appears similar to IC packages.

2020-10-21 Edit: The five econistor sets are gone. Hope we will see them in action..

[jfedison741]

What is tax for you?

General Resistance will charge me sales tax on the shipment, based on my address it is 8.25%.

[jfedison741]

Last year i bought at rhopointcomponents.com and later found that those resistors were somewhat unstable under humidity (about 100 ppm changes seen). I should have five complete sets that i won't use. One set has 120R, 1K, 12K, 2x 70K, 4K7, 10K (all 8G16D, +/- 0,1 %, +/- 5 ppm/K). Last two were meant for amplifier 7 => 10V. If somebody in Germany or EU wants a set, will offer at half price plus postage, please communicate.

Regards, Dieter

Edit about the mentioned humidity test:
That was a very naive test i did when those econistors arrived in June 2019. We have several kg of desiccant for our 3D printer  and i prepared a bag and put one of those resistors inside. Within two weeks there was a 220 ppm change and i stopped watching. So that was a humidity change from 30 or 40 %  down to about 5 or 10 % RH. Repeated the test with another one, similar result. Then i checked an UPW50 and its shift was several times slower. Its enclosure seems to be better, appears similar to IC packages.

Thanks for sharing those humidity test results. That is definitely outside the typical value listed in the the GR datasheet (10 ppm for Moisture resistance, I haven't looked up the test conditions).  Did you inquire with Rhopoint why your resistors may have been so far from typical in terms of moisture resistance? Will keep an eye on this and will let General Resistance know if something looks amiss in the batch for this group buy.

Jeff

[jfedison741]

A quick update:

Here are the requests I have so far (14 sets total):


name                           location         # sets
jfedison741 (Jeff Fedison)      Petaluma, CA       2
alanambrose (Alan Ambrose)      myus.com (UK)      3
syau (Stanley)                  Oregon              2
texaspyro (Mark)                 Texas              2
ezeisel (Eric Zeisel)            San Diego, CA      2      
ffranzini (Francesco)            Houston, TX       2      
jchw4                           USA                 1 + 2x12.0k(0.01%) + 1x4.8k(0.01%)

If you have requested resistors, please review the list above and let me know of any corrections/modifications. I plan to place the order by Monday 26-OCT so please get any final requests in before then.

I will get an updated quote this week and post it here. Will PM you individually for your shipping address. Then will figure out the postage so I can determine your total.

Payment method can be either paypal or venmo, but if needed please feel free to suggest a different payment method.

Jeff

[uski]

Hi,

I am interested in a set, plus an extra 1K resistor (to be used for calibrating meters and so on). Happy to provide details over PM.
Also, do we have a group order of PCBs organizer ? We could do it at the same time.
Otherwise I guess I can order a set from JLCPCB - any special instructions ? Planning to get the PCB gold plated to prevent oxydation

Same for a LTZ1000A... the price break at Digikey is 25 and it's 18$ cheaper so it would make sense to do a group order if we are enough.

Thanks

[RandallMcRee]

Digikey (and other vendors) are out of stock.

You can also order in multiples of 20 direct from AD for $54.50 per. Also backordered at AD, itself. [Backorder
 Est Avail: 2021-02-26]

[uski]

Digikey (and other vendors) are out of stock.

You can also order in multiples of 20 direct from AD for $54.50 per. Also backordered at AD, itself. [Backorder
 Est Avail: 2021-02-26]

Meh. I definitely won't buy a pack of 20. We shoud definitely do a group buy. I assume I'm not alone in not having a LTZ1000A in my parts bin ? 

[jfedison741]

Hi,

I am interested in a set, plus an extra 1K resistor (to be used for calibrating meters and so on). Happy to provide details over PM.
Also, do we have a group order of PCBs organizer ? We could do it at the same time.
Otherwise I guess I can order a set from JLCPCB - any special instructions ? Planning to get the PCB gold plated to prevent oxydation

Same for a LTZ1000A... the price break at Digikey is 25 and it's 18$ cheaper so it would make sense to do a group order if we are enough.

Thanks

Yes, I have you on the list for one set plus an extra 1K. No plans right now for a group buy for the other items but feel free to put one together if desired.
Jeff

[jfedison741]

Ok, I am about ready to place the order. It looks like we will easily meet the order minimum. Here is the final list of requests that I plan to submit as an order to General Resistance on Wednesday Oct. 28. Please note the totals in the table are just the costs of the resistors (I will update later with the tax and shipping amounts per person once I get the invoice from GR).

Please let me know as soon as possilbe if any modifcation is needed. Once I hear back from GR I will post an update here about the order status. Once I have the total cost from GR I will follow-up with each person by PM to exchange shipping and payment info.

Jeff

[jfedison741]

It took a bit longer than expected but the General Resitance Econistor order is now placed. Right now GR is indicating an 8 week lead time. GR will send me a notice when the order is ready to ship and at that point I will update this thread and collect payment & address from each member of the group buy.

[jfedison741]

Here is an update on the group buy: the resistor order has been shipped from General Resistance (Prime Technology). Tracking indicates I should receive it on Friday 04-DEC-2020. I hope to get these sent out to the members of this group next week. Please PM me your shipping address in case you have not already. I will follow-up with a separate PM indicating your total for payment and requesting your shipping address if not already sent.

Best regards,
Jeff